3D打印参数对响应型标签的影响因素有哪些

Additive manufacturing (AM) is an innovative production process that allows for designing objects with self‐responsive properties exploiting the potentialities of nanotechnologies. In this context, acrylonitrile butadiene styrene (ABS) filled with multi‐walled carbon nanotubes (MWCNT) is printed via fusion deposition modeling (FDM) by setting two different printing directions, 0° and 90°. The investigation of the electrical properties of 3D printed parts demonstrates that the printing direction affects the pathway of electrical current flow and, consequently, the heating performance. A suitable setting of the raster angle allows the alignment of the carbon nanotubes along the printing direction. This alignment, verified through morphological investigations, strongly influences the heating properties due to the Joule effect.

The low bioavailability of orally administered drugs as a result of the instability in the gastrointestinal tract environment creates significant challenges to developing site-targeted drug delivery systems. This study proposes a novel hydrogel drug carrier using pH-responsive materials assisted with semi-solid extrusion 3D printing technology, enabling site-targeted drug release and customisation of temporal release profiles. The effects of material parameters on the pH-responsive behaviours of printed tablets were analysed thoroughly by investigating the swelling properties under both artificial gastric and intestinal fluids. It has been shown that high swelling rates at either acidic or alkaline conditions can be achieved by adjusting the mass ratio between sodium alginate and carboxymethyl chitosan, enabling site-targeted release. The drug release experiments reveal that gastric drug release can be achieved with a mass ratio of 1:3, whilst a ratio of 3:1 allows for intestinal release. Furthermore, controlled release is realised by tuning the infill density of the printing process. The method proposed in this study can not only significantly improve the bioavailability of oral drugs, but also offer the potential that each component of a compound drug tablet can be released in a controlled manner at a target location.

Additive manufacturing (AM), commonly referred to as 3D printing, has undergone significant advancements, particularly in the realm of stimuli-responsive 3D printable and programmable materials. This progress has led to the emergence of 4D printing, a fabrication technique that integrates AM capabilities with intelligent materials, introducing dynamic functionality as the fourth dimension. Among the stimuli-responsive materials, Shape Memory Polymers (SMPs) have gained prominence, notably for their crucial applications in stress-absorbing components. However, the exact 3D shape morphing of 4D printed products is affected by both the 3D printing conditions as well as the stimuli activation. Hence it has been hard to precisely control the 3D shape morphing accuracy. To model and optimize the dynamic 3D evolution of the 4D printed parts, we conducted both simulation studies and real-world experiments and introduced a novel machine learning approach extending the concept of normalizing flows. This method not only enables the process optimization of the dynamic 3D profile evolution by optimizing the process conditions during 3D printing and stimuli activation but also provides interpretability for the intermediate shape morphing process. This research contributes to a deeper understanding of the nuanced interplay between process parameters and the dynamic 3D transformation process in 4D printing.

In this work, the focus was on blending polyethylene terephthalate‐1,4‐cyclohexanedimethanol ester (PETG) with poly(ethylene‐co‐octene) (POE) by melt blending in different ratios to develop a novel thermo‐responsive shape memory polymer for 4D printing. SEM images of the blends showed that the compatibility of the blends increased with the increase of POE content and formed a co‐continuous structure at 70% POE content. Mechanical test results showed that the elongation at break of the blends increased significantly with increasing POE content, exhibiting enhanced toughness. Analysis of the DSC and TGA curves identified a thermal transition temperature of 80°C for the blends and confirmed that no thermal decomposition occurred during the 3D printing process. Shape memory performance tests showed that the PETG4/POE6 blend exhibited the best shape memory performance (shape fixation rate of 92.78% and shape recovery rate of 94.72%) and remained stable after 10 test cycles. In addition, the optimal 3D printing parameters were determined by studying printing parameters: layer thickness of 0.1 mm, filler density of 100%, hot‐bed temperature of 70°C, and printing speed of 80 mm/s. Under this parameter, the PETG4/POE6 blends exhibited excellent shape memory performance and rapidly recovered to the initial shape after complex deformation. In conclusion, this study provides a valuable theoretical basis and practical guidance for the development and application of similar shape memory materials in 4D printing.

Based on the traditional additive manufacturing, four-dimensional (4D) printing technology combines structure and shape memory effect (SME), which provides an effective way for the evolution of three-dimensional (3D) printing structure in shape, property and function. However, most of the current researches focus on the influence of printing process parameters on the mechanical properties of parts, and the actuation performance of hybrid conductive polymers is poor. Herein, a method combining 3D printing and coating is proposed to fabricate the electrothermal-responsive three-layer structural flexible actuator of paper-based Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) and multi-walled carbon nanotubes (MWCNTs) composites and polylactic acid (PLA) using 4D printing. The paper-based flexible layer is used as the support layer, the PLA layer made by 3D printing on one side of the paper-based layer is used as the active deformation layer, the MWCNTs/PEDOT:PSS conductive layer coated on the other side of the paper-based layer is used as the electrical actuation layer. The 4D deformation principle of the electrothermal-responsive flexible actuator was analyzed. The influence of printing parameters on the deformation angle of the flexible actuator was analyzed by orthogonal experiment. The experimental results show that the optimal printing parameters are the printing thickness of 0.1 mm, the printing speed of 50 mm s−1, the filling rate of 58%, and the substrate temperature of 60 °C. Under the optimal parameters, the fabricated three-layer structural flexible actuator of paper-based PEDOT:PSS/MWCNTs composites and PLA achieves a larger bending angle of 472.54° under a driving voltage of 25 V. Therefore, the prepared flexible actuator has excellent actuation performance. Moreover, the fabricated flexible actuators are applied in the fields of the flexible hand and the flexible manipulator, which demonstrates the great potential of the flexible actuator in the fields of human-computer interaction and flexible robot.

This study investigates the effects of 3D printing parameters on the shape transformation capabilities of structures fabricated from a composite of 80% PCTG, PET, PTMG, and 20% additives with shape memory properties. Different values of printing speed, infill density, and water temperature after printing have significant effects on the structures of PCTG-based with SMPs that influence the shape memory behaviour. In order to improve the effectiveness and precision of shape recovery under heat stimuli, the research uses the shape memory polymer (SMP) principle to optimize three important parameters, which are printing speed, infill density, and water temperature after printing. Samples were created using fused deposition modeling (FDM) technology across 27 experiments, and their recovery functionality time and thermal responsiveness were then assessed. The project employs Taguchi analysis to analyse the results by using ANOVA method. The results showed that the most important factor influencing shape recovery was the water temperature after printing, which was followed by printing speed and infill density. While lower infill densities improved flexibility and shortened recovery time, higher temperatures led to faster recovery. On the other hand, slower printing speeds lengthened the print time but enhanced interlayer stability and adhesion. A printing speed of 40 mm/s, an infill density of 30%, and a post-printing water temperature of 100°C were found to be the optimal parameter combination, resulting in the quickest recovery time of 7.27 seconds. This study provides important insights for developing 4D printing technologies by highlighting the crucial interaction between printing parameters and external factors in determining the performance of 3D-printed SMP structures. This study fills in gaps in the literature, laying the groundwork for the reliable design and production of smart materials with revolutionary potential.

Abstract Mimicking extracellular matrices holds great potential for tissue engineering in biological and biomedical applications. A key compound for the mechanical stability of these matrices is collagen, which also plays an important role in many intra‐ and intercellular processes. Two‐photon 3D laser printing offers structuring of these matrices with subcellular resolution. So far, efforts on 3D microprinting of collagen have been limited to simple geometries and customized set‐ups. Herein, an easily accessible approach is presented using a collagen type I methacrylamide (ColMA) ink system which can be stored at room temperature and be precisely printed using a commercial two‐photon 3D laser printer. The formulation and printing parameters are carefully optimized enabling the manufacturing of defined 3D microstructures. Furthermore, these printed microstructures show a fully reversible response upon heating and cooling in multiple cycles, indicating successful collagen folding and unfolding. This experimental observation has been supported by molecular dynamics simulations. Thus, the study opens new perspectives for designing new responsive biomaterials for 4D (micro)printing.

Stimuli-responsive hydrogels exhibiting physical or chemical changes in response to environmental conditions have attracted growing attention for the past few decades. Poly(N-isopropylacrylamide) (PNIPAAm), a temperature responsive hydrogel, has been extensively studied in various fields of science and engineering. However, manufacturing of PNIPAAm has been heavily relying on conventional methods such as molding and lithography techniques that are inherently limited to a two-dimensional (2D) space. Here we report the three-dimensional (3D) printing of PNIPAAm using a high-resolution digital additive manufacturing technique, projection micro-stereolithography (PμSL). Control of the temperature dependent deformation of 3D printed PNIPAAm is achieved by controlling manufacturing process parameters as well as polymer resin composition. Also demonstrated is a sequential deformation of a 3D printed PNIPAAm structure by selective incorporation of ionic monomer that shifts the swelling transition temperature of PNIPAAm. This fast, high resolution, and scalable 3D printing method for stimuli-responsive hydrogels may enable many new applications in diverse areas, including flexible sensors and actuators, bio-medical devices, and tissue engineering.

Programmable materials that can reversibly transform between distinct shapes represent a promising technology for applications spanning biomedicine, robotics, and aerospace engineering. Although shape memory polymers offer promising stimuli‐responsive behavior, current manufacturing approaches limit geometric complexity and performance optimization. Here, we demonstrate a manufacturing strategy that combines radiation‐induced crosslinking with additive manufacturing to create programmable shape memory materials with superior performance and architectural control. This study examines radiation crosslinking of 3D printed polycaprolactone‐trimetylolpropane triacrylate (PCL–TMPTA) composites comprised of two different concentrations of TMPTA (2.5% and 5%), revealing fundamental structure–property relationships that enable rational material design. Specimens were fabricated with optimized 3D printing processing parameters and subsequently crosslinked using 60 Co gamma irradiation (5–25 kGy). An unprecedented enhancement in extensional stress from 10 kPa (unirradiated) to 120 kPa (25 kGy) for PCL–TMPTA composites—a 12‐fold improvement—highlights the modification using high energy radiation. Additionally, the delay in relaxation time in stress relaxation reflects the additional macromolecular linkage that critically ensures shape fixity and shape memory behavior. Shape memory evaluation through thermo‐mechanical cycling at 70°C achieved perfect shape fixity ratios of 100% and recovery ratios exceeding 98% for crosslinked specimens, representing state‐of‐the‐art performance. Microstructural analysis via polarized light microscopy and micro‐computed tomography confirmed radiation‐induced morphological evolution and structural integrity preservation during shape memory cycles.

A possible strategy in regenerative medicine is cell-sheet engineering (CSE), i.e., developing smart cell culture surfaces from which to obtain intact cell sheets (CS). The main goal of this study was to develop 3D printing via extrusion-based bioprinting of methylcellulose (MC)-based hydrogels. Hydrogels were prepared by mixing MC powder in saline solutions (Na2SO4 and PBS). MC-based hydrogels were analyzed to investigate the rheological behavior and thus optimize the printing process parameters. Cells were tested in vitro on ring-shaped printed hydrogels; bulk MC hydrogels were used for comparison. In vitro tests used murine embryonic fibroblasts (NIH/3T3) and endothelial murine cells (MS1), and the resulting cell sheets were characterized analyzing cell viability and immunofluorescence. In terms of CS preparation, 3D printing proved to be an optimal approach to obtain ring-shaped CS. Cell orientation was observed for the ring-shaped CS and was confirmed by the degree of circularity of their nuclei: cell nuclei in ring-shaped CS were more elongated than those in sheets detached from bulk hydrogels. The 3D printing process appears adequate for the preparation of cell sheets of different shapes for the regeneration of complex tissues.

Liquid crystal elastomers (LCEs) are polymer networks that exhibit anisotropic liquid crystalline properties while maintaining the properties of elastomers, presenting reversible high-speed and large-scale actuation in response to external stimuli. Herein, we formulated a non-toxic, low-temperature liquid crystal (LC) ink for temperature-controlled direct ink writing 3D printing. The rheological properties of the LC ink were verified under different temperatures given the phase transition temperature of 63 °C measured by the DSC test. Afterwards, the effects of printing speed, printing temperature, and actuation temperature on the actuation strain of printed LCEs structures were investigated within adjustable ranges. In addition, it was demonstrated that the printing direction can modulate the LCEs to exhibit different actuation behaviors. Finally, by sequentially conforming structures and programming the printing parameters, it showed the deformation behavior of a variety of complex structures. By integrating with 4D printing and digital device architectures, this unique reversible deformation property will help LCEs presented here apply to mechanical actuators, smart surfaces, micro-robots, etc.

Thermally responsive shape memory polymers (SMPs) used in 4D printing are often reported to be activated by external heat sources or embedded stiff heaters. However, such heating strategies impede the practical application of 4D printing due to the lack of precise control over heating or the limited ability to accommodate the stretching during shape programming. Herein, we propose a novel 4D printing paradigm by fabricating stretchable heating circuits with fractal motifs via electric-field-driven microscale 3D printing of conductive paste for seamless integration into 3D printed structures with SMP components. By regulating the fractal order and printing/processing parameters, the overall electrical resistance and areal coverage of the circuits can be tuned to produce an efficient and uniform heating performance. Compared with serpentine structures, the resistance of fractal-based circuits remains relatively stable under both uniaxial and biaxial stretching. In practice, steady-state and transient heating modes can be respectively used during the shape programming and actuation phases. We demonstrate that this approach is suitable for 4D printed structures with shape programming by either uniaxial or biaxial stretching. Notably, the biaxial stretchability of fractal-based heating circuits enables the shape change between a planar structure and a 3D one with double curvature. The proposed strategy would offer more freedom in designing 4D printed structures and enable the manipulation of the latter in a controlled and selective manner.

Coaxial 3D bioprinting has advanced the formation of tissue constructs that recapitulate key architectures and biophysical parameters for in-vitro disease modeling and tissue-engineered therapies. Controlling gene expression within these structures is critical for modulating cell signaling and probing cell behavior. However, current transfection strategies are limited in spatiotemporal control because dense 3D scaffolds hinder diffusion of traditional vectors. To address this, we developed a coaxial extrusion 3D bioprinting technique using ultrasound-responsive gene delivery bioinks. These bioink materials incorporate echogenic microbubble gene delivery particles that upon ultrasound exposure can sonoporate cells within the construct, facilitating controllable transfection. Phospholipid-coated gas-core microbubbles were electrostatically coupled to reporter transgene plasmid payloads and incorporated into cell-laden alginate bioinks at varying particle concentrations. These bioinks were loaded into the coaxial nozzle core for extrusion bioprinting with CaCl2 crosslinker in the outer sheath. Resulting bioprints were exposed to 2.25 MHz focused ultrasound and evaluated for microbubble activation and subsequent DNA delivery and transgene expression. Coaxial printing parameters were established that preserved the stability of ultrasound-responsive gene delivery particles for at least 48 h in bioprinted alginate filaments while maintaining high cell viability. Successful sonoporation of embedded cells resulted in DNA delivery and robust ultrasound-controlled transgene expression. The number of transfected cells was modulated by varying the number of focused ultrasound pulses applied. The size region over which DNA was delivered was modulated by varying the concentration of microbubbles in the printed filaments. Our results present a successful coaxial 3D bioprinting technique designed to facilitate ultrasound-controlled gene delivery. This platform enables remote, spatiotemporally-defined genetic manipulation in coaxially bioprinted tissue constructs with important applications for disease modeling and regenerative medicine.

For decades, coaxial printing has been widely applied in 3D tissue engineering scaffold fabrication. However, there are few reports regarding polymeric materials application in shell production due to fabrication constraints. In this study, a combination of cryogenic printing and coaxial printing aims to approach the challenge. Polycaprolactone (PCL) and sodium alginate (SA) were selected as the representative shell and core materials to test the feasibility of the coaxial cryogenic printing by optimizing key parameters, including working temperature, air pressure, PCL, and SA concentration. According to the optical and SEM images, the SA core contracts a string inside the PCL shell, illustrating the shell/core structure of the 3D coaxial PCL/SA scaffolds. Besides, the shell/core 3D scaffold possesses a 38.39 MPa Young’s modulus in mechanical tests; the PCL shell could retain at least 8 h in 5 mol/L HCl solution, leading to a fabricated drug-loaded PCL/SA shell/core “responsive” to acidic pH. In summary, coaxial cryogenic printing was developed to fabricate 3D scaffolds with a PCL/SA shell/core scaffold, broadening the material range of coaxial printing and providing promising applications in drug release.

Soft robots based on stimulus-responsive hydrogels can utilize external stimuli to achieve controllable actuation and perception. Multilayer hydrogel materials can be used to develop stimulus-responsive soft robots with high complexity and stability. In this work, hydrogels with different properties are synthesized by adjusting the component ratio of the poly(N-isopropylacrylamide) (PNIPAM) prepolymer solution. Multilayer hydrogel structures with good mechanical properties and temperature response characteristics are fabricated by using photopolymerization 3D printing technology. In addition, PNIPAM hydrogels are combined with multi-walled carbon nanotubes (MWCNTs) by impregnation to form a composite hydrogel with excellent photo-responsiveness. We put forward the hydrogel structural dynamic model and control equation, unveiled the driving principle and design method of the robot, and determined the key parameters for adjusting dynamics. Inspired by the deformation of frogs, we have designed three bionic miniature soft robots based on multilayer hydrogel structures. They exhibit distinct movement patterns: the tadpole robot achieves an average swimming speed of 0.48 mm/s through tail-wagging motion, the legged tadpole robot reaches a swimming speed of 1 mm/s via leg-kicking propulsion, and the frog robot jumps to a height of 14 mm under visible light stimulation. This work is of great significance for developing hydrogel-based bionic robots, providing valuable insights into the design of visible light-driven robotic systems.

The zinc oxide (ZnO)-grafted polymers have emerged as a prominent material for fabrication of 3D printed biosensor due to its inherent antibacterial, antifungal, room temperature ferromagnetic magnetic behaviour, crystallinity, high thermal conductivity and high exaction binding energy. In this study, ZnO (nanoparticles (NPs)) were grafted with polylactic acid (PLA) using twin-screw compounder for preparations of feedstock filaments. The filaments were prepared by varying input parameters of twin-screw compounder such as ZnO concentration in PLA (0–2%), forced loading (10–15 kg) and torque (0.1–0.2 Nm). Further tests were conducted for thermal properties (on differential scanning calorimetry set-up), mechanical properties (on ultimate tensile testing set-up, Shore D surface hardness, optical photomicrograph-based porosity analysis) and shape memory effect (with stimulus as water under different temperature conditions). The results of the study show that inducing 1% ZnO in PLA led to the formation of highly responsive composite with water as stimulus (at 25°C temperature), mechanically weak, porous, soft surface, while incorporation of 2% ZnO in PLA headed to less porous, harder and responsive composite to the water as stimulus (at 40°C temperature). The proposed combination of ZnO NPs and PLA shows encouraging range of crystallinity, tensile properties and shape memory effect, which made it an eligible candidate for 3D printing applications.

The development of next-generation chemiresistive sensors demands materials that are selective, energy-efficient, and amenable to scalable fabrication for deployment in environmental monitoring, industrial safety, and precision agriculture. This work reports a multifunctional sensing platform based on polymer blend composites engineered to detect a broad spectrum of gas analytes—ranging from polar (ammonia, ethanol) to non-polar (toluene) species—under varying humidity and thermal environments. A binary system of polyvinyl alcohol (PVA) and cellulose acetate butyrate (CAB) is strategically formulated to exploit amphiphilic interactions, while multi-walled carbon nanotubes (MWCNTs) impart a percolative conductive network that enables robust chemiresistive transduction. Phase-separated microstructures generated during drying enhance surface area and diffusivity, enabling rapid response and recovery dynamics at room temperature, with minimal energy input. To advance the processing fidelity and functional performance of these composites, a machine learning (ML)-assisted Direct Ink Writing (DIW) methodology is introduced. Supervised learning algorithms are deployed to identify optimal print parameters—including nozzle speed, extrusion pressure, and filler content—thus minimizing trial-and-error and enabling high-resolution deposition of highly filled, processable inks. The resulting films exhibit tunable thermo-resistive behavior, with electrical resistivity modulating by 6–7 orders of magnitude near 100 °C, along with improved mechanical modulus and strain responsivity. Collectively, this study integrates rational polymer design, intelligent manufacturing, and multi-functional sensing to deliver a versatile materials platform compatible with battery-operated IoT devices, flexible electronics, and distributed sensor networks. The demonstrated synergy between material composition and data-driven processing opens pathways toward the scalable fabrication of adaptive polymer-based electronics for emerging technological applications.

Incorporating shape-morphing capability into 3D microprinting enables the fabrication of 4D-printed microarchitectures as proof-of-concept actuators for potential use in soft robotics and microfluidic systems. The ability of these 3D microstructures to actuate rapidly and reversibly enables precise, non-invasive, and controllable deformation. In this study, we investigated the programmable shape-morphing behavior of 3D microarchitectures fabricated using two-photon polymerization (2PP) of a well-established temperature-responsive hydrogel, poly(N-isopropylacrylamide) (pNIPAM). We first systematically studied how 2PP 3D printing parameters (e.g., laser power, scanning speed) and the chemical composition of pNIPAM, including monomer and crosslinker, influence the shape morphing of bilayer microstructures within a temperature range of ~ 32 °C to 60 °C. The (thermo)mechanical properties of the hydrogels, including the Young’s modulus, thermal expansion coefficients, and angular deflection, were also measured at different laser doses and temperatures. Based on these experimental measurements, we calibrated a thermomechanical model capable of predicting the shape morphing of 4D-printed microarchitectures. These microarchitectures served as proof-of-concept actuators, demonstrating the potential of programmable microscale soft robotics and microfluidic systems. The findings provide design guidelines for engineering stimuli-responsive 3D microstructures, highlighting limitations and opportunities for future integration into functional soft robotic or microfluidic systems made of a single material.

Significant progress in fabricating new multifunctional soft materials and the advances of additive manufacturing technologies have given birth to a new generation of soft robots with complex capabilities, such as crawling, swimming, jumping, gripping, and releasing. Within this vast array of responsive soft materials, hydrogels receive considerable attention due to their fascinating properties, including biodegradable, self-healing, stimuli-responsive, and large volume transformation. Konjac glucomannan (KGM) is an edible polysaccharide that forms a pH-responsive, self-healing hydrogel when crosslinked with borax, and it is the focus of this study. A novel KGM-Borax ink for three-dimensional (3D) printing of free-form structures and soft robots at room temperature is presented. A complete process from ink preparation to the fabrication of a completely cross-linked part is demonstrated. Print setting parameters, rheological properties of the ink and crosslinked gels were characterized. Print quality was found to be consistent across a wide range of print settings. The minimum line width achieved is 650 μm. Tensile testing was carried out to validate the self-healing capability of the KGM-Borax gel. Results show that KGM-Borax has a high self-healing efficiency of 98%. Self-healing underwater was also demonstrated, a rarity for crosslinked gels. The means to form complex structures via 3D printing, reacting to environmental stimuli and the resilience against damage, make this new KGM-Borax gel a promising candidate for the fabrication of the next generation of soft robots.

Poly(lactic acid) (PLA) is a popular material in 3D printing due to its affordability, ease of use, and bio‐based composition. A notable feature of PLA is its ability to undergo self‐deformation when heated above its glass transition temperature (Tg), with deformation behavior adjustable through printing and structural parameters, making it a promising candidate for smart gripping applications. This study quantitatively assesses the self‐deformation performance of an electrically responsive PLA composite activated via Joule heating. Using a testing framework with 3D‐printed U‐shaped samples in two scenarios; the material demonstrates effective self‐bending, achieving over 70% deformation in the first scenario, and a temperature increase up to 80 °C in the second. These findings support the potential of using electro‐responsive PLA in smart gripping applications.

Tunable BioInks for cross-platform 3D printing enable affordable, multilayer biomedical devices. Adjusting viscoelastic and light-responsive parameters apply across SLA, DLP, and extrusion systems.

Precision medicine aims to improve patient outcomes and minimize adverse effects by tailoring drug based therapies to each individual’s characteristics. Magnetically actuated drug delivery systems enable noninvasive, targeted, and on-demand therapeutic release. However, important challenges in the design considerations, including the drug dosage volumes and total dosage incorporated in the design, as well as the ability to batch manufacture such devices with high repeatability, still need to be addressed. In this paper, we explore the role of controlled drug delivery systems with a particular focus on magnetic field-responsive systems and the transformative impact of 3D printing technology. We use stereolithography 3D printing in combination with high-concentration magnetic composite UV curable resins for the fabrication of high-resolution, magnetically actuated drug delivery devices. By optimizing the 3D printing parameters, we achieve structurally consistent and reproducible scaffolds with high geometric fidelity. Our results show that the scaffolds based on 40 w/w% magnetic microparticles and photo-curable resin exhibit strong magnetic responsiveness when applying low magnetic field strengths, leading to compression ratios up to 52.94% and drug release amounts ranging from 8.6 ± 0.5 μl/mm to 135.9 ± 3.1 μl/mm. Comparative analysis of six scaffold designs reveals that the scaffold’s structural configuration can be used to tailor the drug release profile. The presented fabrication method and drug delivery devices are particularly suited for applications demanding accurate dose delivery and remote actuation. We present a proof-of-concept demonstration of our device for precise drug delivery in ophthalmic treatment.

Light-responsive hydrogels are intelligent materials that respond to external light stimuli. When exposed to light, they shrink by releasing water, enabling non-invasive, cost-effective, and remotely controllable actuation. Their adaptability to light parameters such as intensity, direction, wavelength, and irradiation time makes these materials ideal for developing soft robotic actuators. However, hydrogel-based actuators face several challenges due to poor mechanical properties, complex fabrication, and biocompatibility concerns. To address these limitations, this study presents a light-driven 3D-printed elastomer/hydrogel composite actuator. The soft photo-actuator combines TangoPlus, a flexible 3D printing material, with a poly(N-isopropylacrylamide) (PNIPAM) hydrogel copolymerized with the photochromic molecule spiropyran. The study's key contributions include an investigation into prototypes that demonstrate enhanced mechanical integrity, where hydrogel thickness and curing time are shown to affect the actuator's shrinkage response in a predictable manner. Furthermore, a proof-of-concept of a 3D gripping mechanism is proposed to demonstrate the actuator's potential applicability.

This research introduces a novel flexible spherical carbon nanoparticle‐based polyurethane conductive ink, which is employed to fabricate strain sensors by a lab‐developed direct ink writing/3D printing system. Rheological tests are performed, and sensors are pasted on glass fiber‐reinforced plastic specimens to study strain gauge behaviors under quasistatic loading. The gauge factor in tensile loading is found to be layer width dependent as decreasing the strain gauge's layer width increases the sensitivity of the strain sensor. A maximum gauge factor of 34 is achieved using a layer width of 0.2 mm, 17 times greater than commercially available metal foil strain gauges. The four‐point bend tests are performed under tension/compression to assess the sensor's strain‐sensing and damage‐monitoring ability. Fractographic analysis is coupled with strain monitoring using the developed sensor, which confirms that the failure progresses from intralaminar failure modes such as ply splitting in tension. At the same time, delamination leads to kink band formation under compression and the eventual failure of load‐bearing fibers. The developed sensor exhibits repeatable performance with low hysteresis and integrated nonlinearity errors for up to 1000 cycles. The developed sensors could be effectively employed for online in situ structural health monitoring of aerospace structures under static and dynamic loading.

This article reports facile fabrication of a multifunctional smart surface having superhydrophobic self-cleaning property, superoleophilicity, and antimicrobial property. These smart surfaces have been synthesized using the stereolithography (SLA) method of the additive manufacturing technique. SLA is a fast additive manufacturing technique used to create complex parts with intricate geometries. A wide variety of materials and high-resolution techniques can be utilized to create functional parts such as superhydrophobic surfaces. Various materials have been studied to improve the functionality of 3D printing. However, the fabrication of such materials is not easy, as it is quite expensive. In this work, we used a commercially available SLA printer and its photopolymer resin to create various micropatterned surfaces. Additionally, we applied a low surface energy coating with ZnO nanoparticles and tetraethyl orthosilicate to create hierarchical roughness. The wettability studies of created superhydrophobic surfaces were evaluated by means of static contact angle using the sessile drop method and rolling angle measurements. The effects of various factors, including different concentrations of coating mixture, drying temperatures, patterns (pyramids, pillars, and eggbeater structures), and pillar spacing, were studied in relation to contact angles. Subsequently, all the functional properties (i.e., self-cleaning, oleophilicity, and antibacterial properties) of the as-obtained surfaces were demonstrated using data, images, and supporting videos. This inexpensive and scalable process can be easily replicated with an SLA 3D printer and photopolymer resin for many applications such as self-cleaning, oil-water separation, channel-less microfluidics, antibacterial coating, etc.

The development of additive manufacturing equipment and the accessibility of metal powders have recently generated considerable interest in the additive production of smart materials, often known as 4D printing. Recent research centered on ternary alloy systems of NiTi. However, iron shape memory alloy (Fe-SMA), which has outstanding superelasticity and consistent superplastic behavior across a wider temperature range, can provide a valuable counterpart for NiTi SMA. However, the viability and impact of manufacturing processing factors on Fe-SMA alloy are not well understood. The current study examines the impact of laser powder bed fusion (LPBF) processing parameters on Fe-Mn-Al-Ni shape memory alloy characteristics such as crack formation, surface roughness, laser-track morphology, density, dimensional accuracy, hardness, and phase transformation. To effectively capture thermal behavior and gather in-situ fabrication data, in-situ monitoring of sample printing was carried out utilizing a unique sensing system made up of a long wave infrared camera throughout a temperature range of −20 °C to 1500 °C. To characterize the microstructure and phase change of the manufactured samples with respect to manufacturing processing parameters, surface roughness testing, gas pycnometer, Vickers hardness testing, and differential scanning calorimetry (DSC) were used. The research showed that volumetric energy densities (VEDs) between 62 and 93 J.mm−3 produce higher-quality materials with fewer defects, which improved the densification and properties of manufactured Fe-SMA (hardness, density, and porosity).

Additive manufacturing has evolved over the last few decades. Three-dimensional printing is a digital manufacturing technology that provides nearly endless options for the creation of an accessible instrument for all parts of various medical practices, including tissue engineering, through meticulous optimization of material, processing, and geometry for every point in an object. Three-dimensional printing has opened up a new, faster, and safer manufacturing process, despite its incapability to fabricate complex structures and objects. Recently, novel four-dimensional printing techniques have been developed for the transformation of typical stable three-dimensional printed parts into smart objects. The limitations of three-dimensional printing could be remedied with four-dimensional printing, by applying time as the fourth dimension. Self-repairing and speedy printing are two additional benefits of this technology's by using smart materials. By adapting this technology, numerous medical domains could be profited. Four-dimensional printing does not have the ability to produce curved complicated forms. However, five-dimensional printing overcomes the flaws seems in four-dimensional printing. Five-dimensional additive manufacturing relies on the rotation of both the print bed and the extruder head. Five-dimensional printing outlasts in terms of durability than three- and four-dimensional printing. Currently, a combination of the principles of four- and five-dimensional printing into a single process is called six-dimensional printing. In six-dimensional printing, the form changes over time due to the reaction of environmental factors, which is primarily used in biomedical applications. This paper summarizes extensive research on biomaterials in the field of biomedical science and discusses the present implications of three-, four-, five-, and six-dimensional printing techniques.

Additive manufacturing techniques, particularly vat photopolymerization (VPP), have emerged as significant drivers of advancements in materials and technology. VPP offers unparalleled precision and detail in translating complex three-dimensional (3D) forms, making it particularly suitable for smart polymers responsive to external factors such as pH, heat, magnetic fields, electric fields, humidity, light, and temperature. This review comprehensively explores the mechanisms and applications of VPP in fabricating smart polymer-based structures for biomedical purposes. It begins by detailing various VPP methods, highlighting the growing demand for innovative solutions in the biomedical sector. The review further examines the advantages of VPP, including its capability to handle intricate geometries, facilitate rapid prototyping, and provide design flexibility with diverse material options. Additionally, it discusses the challenges and prospects of materials such as bioabsorbable polymers and bioinks, emphasizing their role in bone tissue engineering, dentistry, drug delivery, and tissue regeneration. This review could be a valuable resource for biomedical engineers and clinical researchers seeking to integrate advanced printing technologies into biomedical applications.

The exponential rise of healthcare problems like human aging and road traffic accidents have developed an intrinsic challenge to biomedical sectors concerning the arrangement of patient-specific biomedical products. The additively manufactured implants and scaffolds have captured global attention over the last two decades concerning their printing quality and ease of manufacturing. However, the inherent challenges associated with additive manufacturing (AM) technologies, namely process selection, level of complexity, printing speed, resolution, biomaterial choice, and consumed energy, still pose several limitations on their use. Recently, the whole world has faced severe supply chain disruptions of personal protective equipment and basic medical facilities due to a respiratory disease known as the coronavirus (COVID-19). In this regard, local and global AM manufacturers have printed biomedical products to level the supply–demand equation. The potential of AM technologies for biomedical applications before, during, and post-COVID-19 pandemic alongwith its relation to the industry 4.0 (I4.0) concept is discussed herein. Moreover, additive manufacturing technologies are studied in this work concerning their working principle, classification, materials, processing variables, output responses, merits, challenges, and biomedical applications. Different factors affecting the sustainable performance in AM for biomedical applications are discussed with more focus on the comparative examination of consumed energy to determine which process is more sustainable. The recent advancements in the field like 4D printing and 5D printing are useful for the successful implementation of I4.0 to combat any future pandemic scenario. The potential of hybrid printing, multi-materials printing, and printing with smart materials, has been identified as hot research areas to produce scaffolds and implants in regenerative medicine, tissue engineering, and orthopedic implants.

Acknowledgement: This research/project is supported by SIMTech, A*STAR. ABSTRACT The emergence of 4D printing introduces stimuli-responsive, shape-changing capabilities through additive manufacturing (AM) and smart materials, has advanced the field of soft robotics. However, there are currently lack of methods or tools that capable of aiding in the generative design of 4D AM structures. The current generative design procedure for 4D AM structures often lacks transferability among various structures due to limited understanding of shape memory material behaviors for soft robotics. To develop such a digital library, investigation of fundamental elements, such as material properties of shape memory materials, geometry parameters of design primitives, and 4D printing process parameters are necessary. (1) Material properties of shape memory materials, including shape memory effect, thermal characteristics, and mechanical behaviors, are critical for the material selection of targeted 4D AM structures in soft robotics. (2) Geometry parameters of design primitives, including shape, size, and motion capabilities, are essential to the foundation for creating different morphing systems and programmable structures in the digital library for soft robotics design. (3) Printing process parameters, including infill density, layer thickness, and temperature control, are important for optimizing the fabrication of shape memory components with desired properties and functionalities in soft robotics. As one of the important digital library design primitives, the hinge structure plays a pivotal role in enabling controlled movement and flexibility in 4D AM structures, crucial for soft robotic joint functionality. The designed hinges enable articulation and bending, thus facilitating shape changes and dynamic responses for the generative design of soft robotic morphing systems. In this study, the hinge structures will be fabricated using conventional polylactic acid (PLA) filaments, which exhibit shape memory effects and offer low infill density through fused filament fabrication 4D AM process. (1) To characterize material properties of the PLA filament, such as glass transition temperature, tensile strength, modulus of elasticity, and elongation at break, through dynamic mechanical analysis and static tensile test. (2) To implement the Taguchi method and factorial design of experiment approach to systematically vary hinge geometry parameters, including shape memory properties, such as thickness, width, length, and curvature, for the digital library. (3) To establish the property-structure-process relationship for the 4D printed PLA hinges through the measurement of bending angles and recovery rate. This study will lay the foundation for the creation of an extensive digital library based on various shape memory materials and design primitives for 4D generative design, with a specific focus on soft robotics.

The additive manufacturing of RFID smart tags typically involves printing of antennas using electrically conductive materials along with the hybrid integration of the off-the-shelf low-power electronic components. In this case, the conductivity of printed material could significantly influence the reliable working of electronics as the electromagnetic performance of the antenna depends on it. In this research, we demonstrate the effect of conductive materials for printed antenna and show how their reliable operation could be attained by using suitable number of coatings. The printed antenna with its low-power electronics circuit is also compared with the conventional copper etched rigid and flexible tags to show the challenges regarding the electromagnetic performance. The printed tags are further subjected to different bending cycles to investigate their mechanical stability under varying strain conditions.

No abstract available

The emerging Internet of Things (IoT) paradigm keeps pressure on constant innovation of manufacturing processes, mainly on additive technologies that can significantly reduce waste and cost of manufactured parts. Promising field for high volume, low cost and quick time to market additive fabrication method is printing. This paper briefly compares current printing technologies used for electronics fabrication, mainly for low cost Radio Frequency Identification (RFID), Near Field Communication (NFC) tags, smart labels, smart packaging, sensors etc. with focus on "offset lithography". This method raises a big challenges, one of them is chip contacting method. This work summarizes current contacting methods suitable for printed electronics on flexible substrates with focus on promising contactless RFID magnetic coupling method that does not require conductive connection between chip and antenna itself.

4D (four-dimensional) printing is an innovative manufacturing tool for creating smart, shape-morphing materials extending the capabilities of additive manufacturing (3D printing) to minimise complex manufacturing and part assembly, whilst potentially reducing the energy consumption required in part creation. The purpose of this study is to investigate the feasibility of 4D printing of fibrous constructs utilising discontinuous carbon and glass fibre reinforcements in multilayer architectures. As the final step of 4D printing process, the shape transformation is achieved by controlling the gradient of in-plane thermal shrinkage through the thickness at the single-layer level. A critical understanding of how printing conditions govern the development of anisotropic molecular chain alignment is essential for achieving targeted morphing behaviour. It has been observed that several key factors influence the morphing mechanism, including the alignment of molecules through the nozzle, flow speed changes during deposition, extrusion temperature and post-print cooling rate. Anisotropic molecular chain alignment arises from rapid cooling near the polymer's glass transition temperature, resulting in the locking of aligned molecular chains, and consequently generating shrinkage strain, within the printed multilayer composite. It was observed that asymmetric cooling and complex thermal boundary conditions, coupled with the influence of fibre reinforcement on thermal conductivity and local cooling dynamics, play a significant role in determining the degree of anisotropy. This research demonstrates how multilayer fibre-reinforced composites can be strategically engineered to enable programmable shape-morphing behaviours without relying on dual-material or multi-directional printing; thus, opening new applications for 4D printing of fibre-reinforced components.

In this study, to develop soft pressure sensor applicable to wearable robots using stretchable polymers and conductive fillers, 3.25 wt% carbon nanotubes/thermoplastic polyurethane filament with shore 94 A were manufactured. Three infill densities (20%, 50%, and 80%) and patterns (zigzag (ZG), triangle (TR), honeycomb (HN)) were applied to print cubes via fused filament fabrication 3D printing. Most suitable infill conditions were confirmed based on the slicing images, morphologies, compressive properties, electrical properties, and electrical heating properties. For each infill pattern, ZG and TR divided the layers into lines and figures, and the layers were stacked by rotation. For HN, the same layers were stacked in a hexagonal pattern. Consequently, TR divided layer in various directions, showed the strongest compressive properties with toughness 1.99 J for of infill density 80%. Especially, the HN became tougher with increased infill density. Also, the HN laminated with the same layer showed excellent electrical properties, with results greater than 14.7 mA. The electrical heating properties confirmed that ZG and HN had the high layer density, which exhibited excellent heating characteristics. Therefore, it was confirmed that performance varies depending on the 3D printing direction, and it was confirmed that HN is suitable for manufacturing soft sensors.

The growing demand for sustainable and efficient environmental monitoring systems has driven the development of innovative sensor technologies. This study presents a hybrid ultra-high frequency radio-frequency identification (RFID) sensor tag fabricated on uncoated paper substrate, which constitutes approximately 87% of the tag's mass thereby making the sensor tag more sustainable and eco-friendly. The sensor tag integrates an AS3213C.4 RFID chip together with an antenna, an interdigitated capacitor as a humidity sensor, pads, and interconnects. Temperature sensing is facilitated by the RFID chip's internal temperature sensor, while humidity is monitored through changes in the printed capacitor. All structures except for the chip were screen printed using a conductive silver ink. The silver layer exhibited a thickness of 5.6 μm and a sheet resistance of 56.4 mΩ/sq, sufficient for wireless communication over a distance of 2 m. The sensor was wirelessly interrogated using a Kathrein antenna and reader system, with data retrieved via commercial software. Temperature tests demonstrated accurate readings from 26 °C to 80 °C, aligning with the chip's specifications of −40 °C to 125 °C, with a precision of 1 °C in the range of 10 °C to 50 °C. Humidity measurements in a climate chamber, conducted between 15% and 55% relative humidity, showed an average sensitivity of 0.45% per % humidity change. Hysteresis effects of 7.4% were observed due to the moisture absorption and structural changes of the paper substrate. This work highlights the potential of paper-based sensor tags for sustainable environmental monitoring, aligning with the principles of Industry 4.0 and the Internet of Things (IoT), while addressing the growing challenge of electronic waste.

Continuous glucose monitoring based on the minimally invasive implantation of glucose sensor is characterized by high accuracy and good stability. At present, glucose concentration monitoring based on fluorescent glucose capsule sensor is a new development trend. In this paper, we design a fluorescent glucose capsule sensor with a design optimization study. The motion trajectory of incident light in the fluorescent gel layer is simulated based on the Monte Carlo method, and the cloud maps of light intensity with the light intensity distribution at the light-receiving layer are plotted. Altering the density of fluorescent molecules, varying the thickness of tissue layers, and adjusting the angle of incidence deflection, the study investigates the influence of these parameter changes on the optimal position of reflected light at the bottom. Finally, the simulation results were utilized to design and fabricate a fluorescent glucose capsule sensor. Rabbit subcutaneous tissue glucose level tests and real-time glucose solution concentration monitoring experiments were performed. This work contributes to the real-time monitoring of glucose levels and opens up new avenues for research on fabricating glucose sensors.

This paper presents a novel thermopile-based heat flux sensor utilizing an alumina ceramic substrate. The design innovatively employs the substrate directly as the thermal resistance layer and forms the thermopile through an alternating welding method of thermoelectric wires. Simulation analysis was conducted to investigate the effects of substrate material, thickness, and the number of thermocouple pairs on the sensor’s thermal performance. The results demonstrate that increasing both the substrate thickness and the number of thermocouple pairs significantly enhances the output thermoelectric potential and temperature difference of the sensor; however, an excessively thick substrate considerably prolongs the response time. Performance tests on the fabricated sensors confirmed that the observed trends align well with the simulation results. Moreover, the output voltage exhibits an excellent linear relationship with the heat flux density, achieving a maximum sensitivity of 0.01605 mV/(W/m2).

The limited electrical performance of microelectronic devices caused by low inter-particle connectivity and inferior printing quality is still the greatest hurdle to overcome for Aerosol jet printing (AJP) technology. Despite the incorporation of carbon nanotubes (CNTs) and specified solvents into functional inks can improve inter-particle connectivity and ink printability respectively, it is still challenging to consider multiple conflicting properties in mixture design simultaneously. This research proposes a novel hybrid multi-objective optimization method to determine the optimal functional ink composition to achieve low electrical resistivity and high printed line quality. In the proposed approach, silver ink, CNTs ink and ethanol are blended according to mixture design, and two response surface models (ReSMs) are developed based on the Analysis of Variance. Then a desirability function method is employed to identify a 2D optimal operating material window to balance the conflicting responses. Following that, the conflicting objectives are optimized in a more robust manner in the 3D mixture design space through the integration of a non-dominated sorting genetic algorithm III (NSGA-III) with the developed ReSMs and the corresponding statistical uncertainty. Experiments are conducted to validate the effectiveness of the proposed approach, which extends the methodology of designing materials with multi-component and multi-property in AJP technology.

No abstract available

Hydrogels, owing to their excellent biocompatibility, high water content, and adjustable physicochemical properties, have become indispensable biomaterials in the field of 3D printing. The dynamic boronic ester bond is a reversible covalent bond that can form and dissociate under specific conditions, endowing materials with robust self‐healing capabilities and high sensitivity to external stimuli. By carefully designing materials utilizing dynamic boronic ester bonding, we developed an innovative polymer hydrogel that combines high stability and dynamic characteristics. Specifically, 3‐aminophenylboronic acid (PBA) was successfully grafted onto the natural polysaccharide sodium alginate (SA), resulting in the SA‐PBA moiety. Dynamic boronic ester bonds were then formed by combining SA‐PBA with polyvinyl alcohol (PVA) and MXene (Ti3C2Tx), ultimately yielding SA‐PBA/PVA/MXene 3D printable hydrogel ink (SPPM‐h). The incorporation of MXene was intended to enhance the conductivity of the hydrogel. After thoroughly characterizing the composition and structure of SPPM‐h, we conducted an in‐depth evaluation of its key properties, including rheological behavior, self‐healing ability, and tensile performance. SPPM‐h exhibited remarkable self‐healing properties, achieving complete self‐repair within just 30 s after fracture—significantly faster than some hydrogels reported in the literature, which require up to 24 h for repair. The conductivity of SPPM‐h 3D printing hydrogel ink is approximately 0.034 S/m. Additionally, it demonstrates good adhesion on various types of surfaces, offering broad prospects for applications in direct ink writing 3D printing.

With the convergence and breakthroughs in frontier technologies such as communication systems and artificial intelligence, wearable electronics have entered a new phase of accelerated development. To achieve high-performance yet cost-effective flexible pressure sensors, the coordinated advancement of novel materials, innovative architectures, and advanced manufacturing techniques becomes imperative. This study presents a direct ink writing (DIW) 3D printed graphene -based micro-cone pressure sensor demonstrating an ultra-broad detection range (0-272.2 kPa) coupled with high sensitivity (2.83 kPa⁻¹ in 0-20.1 kPa regime). The device exhibits exceptional dynamic pressure response characteristics and achieves a low detection limit of 49 Pa. Practical validation through human motion monitoring confirms its capability in capturing biomechanical pressure signals, highlighting significant potential for real-time wearable health monitoring applications.

High-performance flexible sensors capable of direct integration with biological tissues are essential for personalized health monitoring, assistive rehabilitation, and human–machine interaction. However, conventional devices face significant challenges in achieving conformal integration with biological surfaces, along with sufficient biomechanical compatibility and biocompatibility. This research presents an in situ 3D biomanufacturing strategy utilizing Direct Ink Writing (DIW) technology to fabricate functional bioelectronic interfaces directly onto human skin, based on a novel annealing PEDOT:PSS/PVA composite bio-ink. Central to this strategy is the utilization of a novel annealing PEDOT:PSS/PVA composite material, subjected to specialized processing involving freeze-drying and subsequent thermal annealing, which is then formulated into a DIW ink exhibiting excellent printability. Owing to the enhanced network structure resulting from this unique fabrication process, films derived from this composite material exhibit favorable electrical conductivity (ca. 6 S/m in the dry state and 2 S/m when swollen) and excellent mechanical stretchability (maximum strain reaching 170%). The material also demonstrates good adhesion to biological interfaces and high-fidelity printability. Devices fabricated using this material achieved good conformal integration onto a finger joint and demonstrated strain-sensitive, repeatable responses during joint flexion and extension, capable of effectively transducing local strain into real-time electrical resistance signals. This study validates the feasibility of using the DIW biomanufacturing technique with this novel material for the direct on-body fabrication of functional sensors. It offers new material and manufacturing paradigms for developing highly customized and seamlessly integrated bioelectronic devices.

Liquid metal (LM) elastomer composites offer promising potential in soft robotics, wearable electronics, and human‐machine interfaces. Direct ink write (DIW) 3D printing offers a versatile manufacturing technique capable of precise control over LM microstructures, yet challenges such as interfilament void formation in multilayer structures impact material performance. Here, a DIW strategy is introduced to control both LM microstructure and material architecture. Investigating three key process parameters–nozzle height, extrusion rate, and nondimensionalized nozzle velocity–it is found that nozzle height and velocity predominantly influence filament geometry. The nozzle height primarily dictates the aspect ratio of the filament and the formation of voids. A threshold print height based on filament geometry is identified; below the height, significant surface roughness occurs, and above the ink fractures, which facilitates the creation of porous structures with tunable stiffness and programmable LM microstructure. These porous architectures exhibit reduced density and enhanced thermal conductivity compared to cast samples. When used as a dielectric in a soft capacitive sensor, they display high sensitivity (gauge factor = 9.0), as permittivity increases with compressive strain. These results demonstrate the capability to simultaneously manipulate LM microstructure and geometric architecture in LM elastomer composites through precise control of print parameters, while maintaining geometric fidelity in the printed design.

3D printing technology is one of the most promising strategies for constructing topological functional materials. The development of functional inks is a core issue in the technical development of 3D printing technology. In this study, we engineered photonic crystal inks based on chiral nematic liquid crystals of cellulose derivative, i.e. hydroxypropyl cellulose (HPC), and applied it to direct-ink-writing (DIW) 3D printing technology. We modified hydroxypropyl cellulose by etherification reaction to obtain photo-cross-linkable water-soluble hydroxypropyl cellulose acrylate (HPCA) with different degrees of substitution (DS). We comprehensively explored the effect of the DS on the initial concentration of formed chiral nematic liquid crystal and quantitatively, analyzed the relationship between the DS and the helical structure of the chiral nematic structure. We used photo cross-linkable chiral nematic HPCA as photonic crystal ink to construct structure-color 3D objects of diverse shapes. The constructed structure-color objects showcase robust tolerance against temperature and acidic conditions (pH = 1). Moreover, the color of the constructed objects is independent of the observation angle. The photonic crystal ink based on chiral nematic liquid crystals of biodegradable polysaccharide materials is expected to have excellent market prospects in the fields of such as smart packaging and optical devices.

Fabrication of structures in unstructured environments is a promising field to expand the application spaces of additive manufacturing (AM). One potential application is to add new components directly onto existing structures. Herein, a versatile, reconfigurable direct ink writing (DIW) manufacturing method is developed in tandem with a two‐stage hybrid ink designed to fabricate high‐strength, self‐supporting parts in unconventional printing spaces such as underneath a build surface or horizontally. This two‐stage hybrid DIW ink combines a photopolymer and a tough epoxy resin. The photopolymer can cure rapidly to enable layer‐by‐layer printing of complex structures. It also possesses adequate adhesion to allow the fabrication of large volume structures on a diversity of substrates including acrylic, wood, glass, aluminum, and concrete. The epoxy component can cure after 72 h in ambient conditions with further increased adhesion strengths. The capabilities of the reconfigurable DIW extrusion nozzle method to print complex structures in inverted and horizontal environments are demonstrated. Finally, via addition of DIW‐deposited conductive paths, a functional 3D‐printed structure capable of in situ deformation monitoring is created. This work has the potential to be used for applications such as appending new parts to existing structures for increasing functionality, repair, and structure health monitoring.

Functional nanowire ink formulations require elaborate control over their composition, rheological properties, and fluidic properties to optimize their printing processes. They also require harsh post-fabrication treatments to maximize the performance of the resulting printed flexible devices, making it challenging to uniformly deposit nanowire-based architectures and ensure device reproducibility and scalability. Here, we propose a strategy for developing silver nanowire (AgNW) ink formulations, where hyperbranched molecules (HPMs) are employed as both dispersant and stabilizer for nanowires. The three-dimensional architecture with functional groups on the periphery of HPMs enables the preparation of thixotropic HPMs-AgNW inks with solid contents of up to 20 wt.% in both aqueous and organic solvents using a low amount of HPMs (AgNW and HPMs weight ratio = 1:0.001). The HPMs-AgNW inks can be printed into patterns with a resolution of 20 μm on various flexible substrates without needing harsh post-treatments. We obtain bar-coated transparent electrodes (sheet resistance of 17.1 Ω sq−1 at 94.7% transmittance), slot-die-coated flexible conductive patterns, screen-printed conductive lines (conductivity exceeding 6.2 × 104 S cm−1), and 3D printed stretchable wires. Importantly, this HPMs-stabilized formulation strategy is general for various functional nanowires, enabling the integration of a diverse set of nanowire-based wearable electronic systems. Depositing flexible electronics based on nanowires uniformly and reproducibly is a challenge. Here, the authors demonstrate the formulation of silver nanowire suspensions using hyperbranched molecules that enable scalable fabrication of electrodes with different printing technologies.

Additive manufacturing is a promising technique for offering novel functionality to various materials by creating three-dimensional (3D) structures. However, the development of sustainable synthesis processes for 3D printing inks or 3D-printed materials remains a major challenge. In this work, a simple two-step mixing approach is developed to prepare a 3D printing ink from green, low-cost, and low-toxicity materials [commercial Carbopol and deep eutectic solvents (DESs)]. A small weight fraction of Carbopol can impart desired rheological properties to the DES used in the 3D printing ink and also can significantly enhance the stretchability of eutectogels up to 2500% strain. The 3D-printed auxetic structure shows a negative Poisson's ratio (within 100% strain), high stretchability (300%), high sensitivity (gauge factor of 3.1), good moisture resistance, and sufficient transparency. It can detect human motion with high skin comfort and breathability. The results of this work highlight a green, low-cost, and energy-saving strategy to fabricate conductive microgel-based inks for 3D printing of wearable devices.

Anisotropic pressure sensors are gaining increasing attention for next‐generation wearable electronics and intelligent infrastructure owing to their sensitivity in identifying different directional forces. 3D printing technologies have unparalleled advantages in the design of anisotropic pressure sensors with customized 3D structures for realizing tunable anisotropy. 3D printing has demonstrated few successes in utilizing piezoelectric nanocomposites for anisotropic recognition. However, 3D‐printed anisotropic piezoresistive pressure sensors (PPSs) remain unexplored despite their convenience in saving the poling process. This study pioneers the development of an aqueous printable ink containing waterborne polyurethane elastomer. An anisotropic PPS featuring tailorable flexibility in macroscopic 3D structures and microscopic pore morphologies is created by adopting direct ink writing 3D printing technology. Consequently, the desired directional force perception is achieved by programming the printing schemes. Notably, the printed PPS demonstrated excellent deformability, with a relative sensitivity of 1.22 (kPa*wt. %)−1 over a substantial pressure range (2.8 to 8.1 kPa), approximately fivefold than that of a state‐of‐the‐art carbon‐based PPS. This study underscores the versatility of 3D printing in customizing highly sensitive anisotropic pressure sensors for advanced sensing applications that are difficult to achieve using conventional measures.

Shaping soft and conductive materials into sophisticated architectures through 3D printing is driving innovation in myriad applications, such as robotic counterparts that emulate the synergic functions of biological systems. Although recently developed multi‐material 3D printing has enabled on‐demand creation of intricate artificial counterparts from a wide range of functional viscoelastic materials. However, directly achieving complementary functionalities in one ink design remains largely unexplored, given the issues of printability and synergy among ink components. In this study, an easily accessible and self‐regulating tricomponent ionogel‐based ink design to address these challenges is reported. The resultant 3D printed objects, based on the same component but with varying ratios of ink formulations, exhibit distinct yet complementary properties. For example, their Young's modulus can differ by three orders of magnitude, and some structures are rigid while others are ductile and viscous. A theoretical model is also employed for predicting and controlling the printing resolution. By integrating complementary functionalities, one further demonstrates a representative bioinspired prototype of spiderweb, which mimics the sophisticated structure and multiple functions of a natural spiderweb, even working and camouflaging underwater. This ink design strategy greatly extends the material choice and can provide valuable guidance in constructing diverse artificial systems by 3D printing.

The development of the effective 3D printing strategy for diverse functional monomers is still challenging. Moreover, the conventional 3D printing hydrogels are usually soft and fragile due to the lack of an energy dissipation mechanism. Herein, a microsphere mediating ink preparation strategy is developed to provide tailored rheological behavior for various monomer direct ink writings. The chitosan microspheres are used as an exemplary material due to their tunable swelling ratio under the acid-drived electrostatic repulsion of the protonated amino groups. The rheological behaviors of the swollen chitosan microsphere (SCM) are independent on the monomer types, and various functional secondary polymers could be carried at a wide loading ratio by the acid driving. The SCM reinforces the hydrogel as the sacrificial bonds. With the adjustable composition, the 3D printing hydrogel mechanical properties are tunable in wide windows: strength (0.4-1.01 MPa), dissipated energy (0.11-3.25 MJ m-3), and elongation at break (47-626%). With the excellent printing and mechanical properties, the SCM inks enable multi-functional integration for soft device production, such as 4D printing robots and wearable strain sensors. We anticipate that this microsphere mediating 3D printing strategy can inspire new possibilities for the design of the robust hydrogels with a broad range of functionalities and mechanical performances.

Flexible capacitive pressure sensors are critical components in emerging applications such as electronic skin, human‐machine interfaces, and soft robotics. However, achieving a balance between high sensitivity and a wide linear range remains a key challenge. Here, a synergistic strategy is reported that integrates printable gradient‐modulus hydrogels with microstructured architectures to mitigate this performance trade‐off. It is revealed that MXene plays a critical role in fine‐tuning the elastic moduli of the hydrogel inks via the so‐called MXene triggering chemistry, the latter greatly boosts the radical generation for rapid polymerization kinetics. This enables the minutes‐scale printing of vertically modulus‐graded (stiff‐medium‐soft layers from top to bottom) microdome structures. Such a rational design effectively delays the structural densification and achieves progressive, layer‐by‐layer deformation under pressure, leading to a high sensitivity of 538 kPa −1 across a broad pressure range (up to 440 kPa). The great potential of the rapid‐printed pressure sensing arrays in recognizing object stiffness is further demonstrated, and provides real‐time spatial capacitance feedback during grasping tasks by integrating into a robotic gripper. This work offers a scalable and programmable strategy for innovating material modulus and structural geometry, opening new pathways toward high‐performance tactile sensors for intelligent sensing and adaptive robotics.

Functional fabrics have broad applications in smart wearables, offering diverse functions, such as sensing, energy harvesting, and actuation. The use of 3D printing to deposit functional materials onto textile fabrics has emerged as a transformative approach in smart wearable development due to the advantages it offers. However, achieving the desired functionalities while maintaining the fabric’s flexibility, wearing comfort, washability, and durability of the printed material remains a challenge. In this study, direct ink writing (DIW) 3D printing technology was employed to print polybutylene succinate (PBS) solutions containing carbon nanotubes (CNTs) onto two types of fabrics. Various properties of the printed fabrics were assessed to examine the influence of printing solutions, fabric structures, and postprinting processes on printing performance. The printed fabrics exhibited excellent electrical conductivity, mechanical strength, gauge factor, and stability under repeated strains. These characteristics highlight their potential for use in smart wearable devices such as strain- and motion-detecting sensors. Analysis of the printed fabric morphologies revealed that factors such as fiber content, yarn structure, and surface roughness of the substrate fabric, along with the rheological properties and surface tension of the printing solution, played key roles in determining the wetting and penetration behaviors of the solution on the substrate. The solution’s ability to penetrate and bond with fibers provided the printed fabrics with enhanced washability and abrasion resistance, demonstrating the advantages of DIW printing technology in developing textile-based sensors for smart wearables. Additionally, by using biobased and biodegradable nontoxic Cyrene as the solvent for processing, the printed fabric is safer for smart wearables, and the process is more environmentally friendly than commonly used toxic solvents for PBS.

In nature, structural and functional materials often form programmed three-dimensional (3D) assembly to perform daily functions, inspiring researchers to engineer multifunctional 3D structures. Despite much progress, a general method to fabricate and assemble a broad range of materials into functional 3D objects remains limited. Herein, to bridge the gap, we demonstrate a freeform multimaterial assembly process (FMAP) by integrating 3D printing (fused filament fabrication (FFF), direct ink writing (DIW)) with freeform laser induction (FLI). 3D printing performs the 3D structural material assembly, while FLI fabricates the functional materials in predesigned 3D space by synergistic, programmed control. This paper showcases the versatility of FMAP in spatially fabricating various types of functional materials (metals, semiconductors) within 3D structures for applications in crossbar circuits for LED display, a strain sensor for multifunctional springs and haptic manipulators, a UV sensor, a 3D electromagnet as a magnetic encoder, capacitive sensors for human machine interface, and an integrated microfluidic reactor with a built-in Joule heater for nanomaterial synthesis. This success underscores the potential of FMAP to redefine 3D printing and FLI for programmed multimaterial assembly. A freeform multimaterial assembly process (FMAP) is demonstrated, synchronizing laser induction with 3D printing for seamlessly integrating multimaterials into 3D objects, enabling streamlined, flexible, and precise electronic device fabrication.

Rewritable photonic crystal (PC) paper has the potential to significantly reduce the consumption of forest resources in the printing industry, while also being environmentally friendly and efficient. However, traditional PC papers based on solvent or photothermal responses can lead to diffusion, which can hinder printing accuracy. In this study, a novel rewritable PC paper compatible with pin‐printing is presented based on a pressure‐responsive shape‐memory PC paper. High‐resolution printing can be realized by both computer‐programmed 3D‐printed seals and pin‐printing techniques. The information written on this PC rewritable paper can be erased by water, enabling the paper to be rewritten and reused at least 8 times without any change in performance. Furthermore, the information stored on the PC paper is stable and can be stored in ordinary environments for at least 6 months without fading. The PC paper has the capability of multicolor printing with a precision finer than 100 μm and has potential in office papers, smart price tags, and anti‐counterfeiting labels.

In this article, we introduce and demonstrate a smart acetabular trail with embedded photonic sensor arrays for force and contact location sensing. Finite element modeling is performed to study the strain distribution when an external force is loaded to the acetabular trail model, which is applied to guide strain sensor array routing. Then acetabular trail with sensor embedded channels is fabricated through polymer stereolithography (SLA) 3-D printing process. Intrinsic Fabry-Perot interferometer (IFPI) based optical fiber sensors are employed for in situ monitoring of local strain variation, thanks to their high spatial resolution. As a proof of concept, ten IFPI sensors are embedded for strain mapping. Experimental results demonstrate that localized strain change is captured by the IFPI spectra variation and loading force position can be estimated through the obtained strain distribution. With enhanced sensor robustness, strain distribution and contact location monitoring capability, this proposed smart acetabular trail could be attractive for intelligent medical applications, especially in total hip arthroplasty (THA).

We describe a 3-in-1 detector for simultaneous contactless conductivity (C4D), ultraviolet absorbance (UV-AD), and laser-induced fluorescence (LIF) measurements on a single detection point for capillary electrophoresis (CE). A key component of the detector was a rectangular detector head that was assembled with four 3D-printed parts. Two parts covering the detector head to function as a Faraday cage were fused deposition modeling printed using an electrically conductive material. The other two parts in between the conductive parts were stereolithography (SLA) printed with high-resolution (50 μm) constructions on the surface. After assembling the two SLA printed parts, several cavities were built with the surface constructions. Two electrodes and a Faraday shield for C4D were cast by injecting molten Wood's metal into the cavities. For UV-AD, a slit (100 μm width) was created by putting together two grooves (50 μm depth) on the surface of the SLA printed parts. A 255 nm UV-LED was used as the light source. The effective path length and stray light for a 50 μm id capillary were 39 μm and 13%, which were superior to those of other reported 3D-printed AD detectors. Confocal LIF detection was conducted by using an objective lens to focus the laser on the capillary via a through-hole. The detector was used to detect model analytes, including inorganic and organic ions, and fluorescein isothiocyanate labeled amino acids in a signal-run CE separation. In detecting fluorescein, LODs were 1.3 μM (C4D), 2.0 μM (UV-AD), and 1 nM (LIF). The calibration ranges covered from 0.01 μM to 500 μM.

We report on the fabrication of 3D printed pH-responsive and antimicrobial hydrogels with a micrometer-scale resolution achieved by stereolithography (SLA) 3D printing. The preparation of the hydrogels was optimized by selecting the most appropriate difunctional polyethylene glycol dimethacrylates (testing cross-linking agents with chain lengths ranging from 2 up to 14 units ethylene glycol) and introducing acrylic acid (AA) as a monofunctional monomer. As a result of the incorporation of AA, the hydrogels described are able to reversibly swell and shrink upon environmental changes on the pH, and the swelling extent is directly related to the amount of AA and can be thus finely tuned. More interestingly, upon optimization of the UV penetration depth employing a photoabsorber (Sudan I), a reliable procedure for the fabrication of 3D objects with a high model accuracy is shown. Finally, the antimicrobial properties of all of the hydrogels were demonstrated using Staphylococcus aureus as a bacterial model. We found that even those hydrogels with a low amount of AA monomeric units presented excellent antimicrobial properties against S. aureus.

This study investigates the mechanical and viscoelastic properties of TC-85, a biocompatible material specifically designed for orthodontic applications, with a focus on how temperature variations influence its mechanical and viscoelastic properties and their relevance to clinical outcomes. Using a Digital Light Processing (DLP) 3D printer, the photosensitive resin TC-85 is printed, and extensive thermo-mechanical testing is conducted, which includes evaluations of tensile modulus, stress relaxation, and creep behavior. Dynamic Mechanical Analysis (DMA) is conducted at temperatures varying from 30 to 45 °C to assess the material’s adaptive response to thermal fluctuations. TC-85 is distinguished by its unique mechanical properties, which include a temperature-sensitive stiffness, stress relaxation capability, and shape memory feature. The results demonstrate that TC-85 maintains an enhanced level of residual force and a faster recovery of strain through numerous cycles of loading and unloading. At 40 °C, TC-85 displays a substantial reduction in its storage modulus, while maintaining consistent strain recovery and volumetric constancy. The study highlights TC-85’s potential in orthodontic treatments, providing adaptable mechanical and viscoelastic properties that enable the exertion of consistent and regulated forces on teeth. Its resistance to force decay, stable volume at raised temperatures, and shape memory properties enhance hygienic maintenance and patient comfort, positioning TC-85 as a pioneering material for the next generation of clear aligners.

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Despite advances in osteomyelitis treatment, achieving spatiotemporal coordination of infection control and bone regeneration remains challenging due to bacterial-induced acidic microenvironments and toxin-mediated osteoblast dysfunction. Herein, a novel 3D-printed chitosan-based composite scaffold (VM@n-HA/CS/DM) was developed. The scaffold strategically integrates two functional components: (1) Vancomycin-loaded chitosan microspheres (VM) conjugated with scaffold via pH-sensitive Schiff base bonds formed between aldehyde and amine groups, selectively breaking down in the acidic microenvironment of bacterial infections, thereby enabling on-demand release of vancomycin (Van) to target and eliminate Staphylococcus aureus (S. aureus). (2) Diflunisal-loaded chitosan microspheres (DM) dispersed within the scaffold matrix, providing sustained release to suppress alpha-type phenol-soluble modulins (PSMs) expression and shield osteoblasts from bacterial toxins. The scaffold employs pH-responsive and diffusion-mediated mechanisms to match the timing of infection control and bone regeneration. Furthermore, the 3D-printed hierarchical porous structure, with spatially optimized microsphere/matrix distribution, ensures dual functionality: multiscale porosity facilitates nutrient transport and cell infiltration while maintaining mechanical integrity, and compartmentalized drug delivery achieves precise therapeutic control. This dual therapeutic modality advances osteomyelitis treatment by providing a clinically viable strategy to address persistent challenges.

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The pH-responsive drug release approach in combination with three-dimensional (3D) printing for colon-specific oral drug administration can address the limitations of current treatments such as orally administered solid tablets. Such existing treatments fail to effectively deliver the right drug dosage to the colon. In order to achieve targeted drug release profiles, this work aimed at designing and producing 3D printed tablet shells using Eudragit® FS100 and polylactic acid (PLA) where the core was filled with 100 µL of N-acetylglucosamine (GlcNAc)-loaded methyl cellulose (MC) hydrogel. To meet the requirements of such tablets, the effects of polymer blending ratios and MC concentrations on physical, thermal, and material properties of various components of the tablets and most importantly in vitro drug release kinetics were investigated. The tablets with 80/20 weight percentage of Eudragit® FS100/PLA and the drug-loaded hydrogel with 30 mg/ml GlcNAc and 3% w/v MC showed the most promising results having the best printability, processability, and drug release kinetics besides being non-cytotoxic. Manufacturing of these tablets will be the first milestone in shifting from the conventional "one size fits all" approach to personalized medicine where different dosages and various combinations of drugs can be effectively delivered to the inflammation site.

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Gastric acid secretion is closely associated with the development and treatment of chronic gastritis, gastric ulcers, and reflux esophagitis. However, gastric acid secretion is affected by complex physiological and pathological factors, and real-time detection and control are complicated and expensive. A gastric delivery system for antacids and therapeutics in response to low pH in the stomach holds promise for smart and personalized treatment of stomach diseases. In this study, pH-responsive modular units were used to assemble various modular devices for self-regulation of pH and drug delivery to the stomach. The modular unit with a release window of 50 mm2 could respond to pH and self-regulate within 10 min, which is related to its downward floatation and internal gas production. The assembled devices could stably float downward in the medium and detach sequentially at specific times. The assembled devices loaded with antacids exhibited smart pH self-regulation under complex physiological and pathological conditions. In addition, the assembled devices loaded with antacids and acid suppressors could multi-pulse or prolong drug release after rapid neutralization of gastric acid. Compared with traditional coating technology, 3D printing can print the shell layer by layer, flexibly adjust the internal and external structure and composition, and assemble it into a multi-level drug release system. Compared with traditional coating, 3D-printed shells have the advantage of the flexible adjustment of internal and external structure and composition, and are easy to assemble into a complex drug delivery system. This provides a universal and flexible strategy for the personalized treatment of diseases with abnormal gastric acid secretion, especially for delivering acid-unstable drugs.

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Due to the miniaturization of equipment for flow chemistry and microprocess engineering, low-cost sensors and analytical devices are becoming increasingly important for automated inline process control and monitoring. The combination of 3D printing technology and open-source lab automation facilitates the creation of a microfluidic toolbox containing tailored actuators and sensors for flow chemistry, enabling a flexible and adaptable design and efficient processing and control based on the measured data. This contribution presents a set of 3D-printed microfluidic sensor flow cells for inline measurement of temperature, electrical conductivity (EC), and pH value, while compensating for the temperature dependence of EC and pH. The tailored sensor flow cells were tested using model reactions in a single-phase capillary flow system. They have an accuracy comparable to reference sensors in batch measurements. The sensor data can be used to monitor the reaction progress (conversion), determine the kinetic data (activation energy, pre-exponential factors) of saponification reactions, and identify titration characteristics (equivalence and isoelectric points) of neutralization reactions. Hence, the 3D-printed microfluidic sensor flow cells offer an attractive alternative to commercial analytical flow devices for open-source and low-cost lab automation.

The rapid and personalized management of wound infections remains a significant clinical challenge. This study addresses this need by developing a smart, dual-nozzle 3D-printed theranostic hydrogel pad for on-demand wound care. The platform is based on a tailor-made Pluronic F127-dimethacrylate (PF127-DMA) hydrogel, synthesized to provide optimal printability and dual-functionality. This enables the simultaneous extrusion of two distinct bioinks: a diagnostic ink containing bromocresol purple for pH sensing and a therapeutic ink loaded with graphene oxide (GO) and the antibiotic levofloxacin. The fabricated construct acts as an intelligent wound dressing, providing a distinct visual colorimetric response to differentiate healthy skin pH (4.0-6.0) from pathogenic, alkaline infection conditions (pH 7.4-8.0). Simultaneously, the system provides pH-responsive controlled drug release, with a significantly enhanced cumulative levofloxacin release of 171.68 ± 1.59 µg at pH 8.0 compared to 134.34 ± 1.46 µg at pH 7.4, demonstrating its ability for infection-triggered therapy. The incorporation of graphene oxide was found to critically improve drug release kinetics and promote intramatrix accumulation. Furthermore, in vitro MTT assays confirmed the high biocompatibility of the hydrogel platform. By integrating real-time visual monitoring with controlled antimicrobial release, this 3D-printed theranostic system presents a promising and scalable strategy for advanced wound management.

Accurate temperature monitoring plays a crucial role in understanding the physiological status of patients and the early diagnosis of diseases commonly associated with local and global infections. Intradermal temperature measurement is, in principle, more precise than skin surface detection, as it prevents interference from environmental temperature changes and skin secretions. However, to date, precise and reliable intradermal temperature monitoring in a real-time and continuous manner remains a challenge. We propose herein high-resolution 3D printing to fabricate a mechanically robust and biocompatible hollow microneedle, filled with a temperature-responsive conducting polymer (poly(3,4-ethylenedioxythiophene): polystyrenesulfonate, PEDOT:PSS) to develop a microneedle temperature sensor (T-MN). The significance is 2-fold: rational design of robust MNs with high resolution in the micrometer domain and the implementation of a conducting polymer in a MN format for temperature sensing. The analytical performance of the developed T-MN is in vitro evaluated under mimicked intradermal conditions, demonstrating good sensitivity (−0.74%° C–1), resolution (0.2 °C), repeatability (RSD = 2%), reproducibility (RSD = 2%), reversibility, and medium-term stability. On-body temperature monitoring is performed on six euthanized rats for 80 min. The results presented good agreement with those obtained using a commercial optical temperature probe, which was intradermally inserted into the rat skin. The reliability of utilizing the T-MN for precise and continuous intradermal temperature monitoring was successfully demonstrated, noting its potential use for patient monitoring in the near future but also temperature compensation for MN (bio)sensors that may need it.

In additive manufacturing via fused deposition modeling (FDM), no easily scalable process for producing intelligent, e.g., pH‐responsive, structurally colored filaments is known yet. This work presents the preparation of a structurally colored and pH‐responsive filament for 3D printing via fused deposition modeling (FDM). The filament consists of tailored core–shell particles exhibiting an inherent pH‐responsive behavior due to the incorporation of poly(methacrylic acid) in the particle shell. The filament and 3D‐printed objects exhibit distinct structural coloring, exerting a clear color change when exposed to alkaline environments. The core–shell particles used are accessible via scalable stepwise emulsion polymerization in starved‐feed mode, followed by freeze‐drying. Through the targeted incorporation of additives and the extrusion of core–shell particles, a filament is produced, which is then utilized for 3D FDM printing. The particle design was adjusted, and the obtained materials were investigated with respect to their thermal, optical, and mechanical properties to gain a deeper understanding of the material's behavior. To gain additional insights, the obtained core–shell particles are also melt‐sheared to produce 2D pH‐responsive opal films. The material presented herein is a promising platform for smart sensing, secret information encoding, and anti‐counterfeiting applications in complex 3D‐printed objects.

Polymer-based host–guest organic room-temperature phosphorescent (RTP) materials are promising candidates for new flexible electronic devices. Nowadays, the insufficient fabrication processes of polymeric RTP materials have hindered the development of these materials. Herein, we propose a strategy to realize 3D printable organic RTP materials and have successfully demonstrated real-time sensing and display devices through a Digital Light Processing (DLP) 3D printing process. We have designed and synthesized the molecules EtCzBP, PhCzBP and PhCzPM with A–D–A structures. The crucial role of strong intramolecular charge transfer (ICT) at the lowest triplet states in achieving bright photo-activated phosphorescence in polymer matrices has also been demonstrated. 3D printable RTP resins were manufactured by doping emissive guest molecules into methyl methacrylate (MMA). Based on these resins, a series of complex 3D structures and smart temperature responsive RTP performances were obtained by DLP 3D printing. Additionally, these RTP 3D structures have been applied in real-time temperature sensing and display panels for the first time. This work not only provides a guiding strategy for the design of emissive guest molecules to realize photo-activated RTP in poly(methyl methacrylate) (PMMA), but also paves the way for the development of 3D-printable real-time sensing structures and new-concept display devices.

Liquid crystal elastomers with near-ambient temperature-responsiveness (NAT-LCEs) have been extensively studied for building biocompatible, low-power consumption devices and robotics. However, conventional manufacturing methods face limitations in programmability (e.g., molding) or low nematic order (e.g., DIW printing). Here, a hybrid cooling strategy is proposed for programmable three-dimensional (3D) printing of NAT-LCEs with enhanced nematic order, intricate shape forming, and morphing capability. By integrating a low-temperature nozzle and a cooling platform into a 3D printer, the resulting temperature field synergistically facilitates mesogen alignment during extrusion and disruption-free ultraviolet (UV) cross-linking. This method achieves a nematic order 3000% higher than NAT-LCEs fabricated using traditional room temperature 3D printing. Enabled by shifting of transition temperature during hybrid cooling printing, printed sheets spontaneously turn into 3D structures after release from the platform, exhibiting bidirectional deformation with heating and cooling. By adjusting the nozzle and plate temperatures, NAT-LCEs with graded properties can be fabricated for intricate shape morphing. A wristband system with enhanced heart rate monitoring is also developed based on 3D-printed NAT-LCE. Our method facilitates developments in soft robotics, biomedical devices, and wearable electronics.

Temperature monitoring within the cold chain, essential for safety of perishable products, typically employs devices such as battery-powered data loggers and radio-frequency identification tags. Such devices include non-eco-friendly components, posing challenges for their safe disposal and recycling. This study demonstrates the fabrication of a fully ecoresorbable, chipless, and wireless temperature-responsive tag, designed to irreversibly track temperature changes through a permanent shift in resonance frequency. The tag is printed on a customized moisture-resistant poly(β-hydroxybutyrate)-cellulose composite substrate. An RLC circuit made of printed zinc metallic traces, encapsulated with beeswax to prevent oxidation, enables seamless wireless operation. The tag utilizes bio-based phase-changing materials such as frozen olive, jojoba, and coconut oils to induce irreversible resonance frequency shifts of more than 30 MHz at respective melting points of 8 °C, 15 °C, and 25 °C. A cellulose capillary element efficiently absorbs the melted oil, enabling reliable operation at inclinations from 0° to 90°. At the end of its service life, the device can undergo disintegration in a compost environment within 9 weeks. This work demonstrates a sustainable chipless technology from material selection and manufacturing processes to end-of-life disposal as an advanced thermal indicator solution for cold chain temperature-excursion detection. The authors demonstrate a chipless and wireless temperature tag using a biopolymer and printed zinc. Bio-based phase-change materials enable irreversible thermal detection, and the device fully disintegrates in compost, supporting transient electronics.

Flexible pressure sensors, as an emerging pressure-sensitive element with sensing ability similar to human skin, have a broad application prospect in the fields of health monitoring, e-skin, intelligent robotics and so on. Herein, a flexible pressure sensor array printed based on DIW (Direct Ink Writing, is an additive manufacturing technology that realizes complex patterns by controllable extrusion of functional inks for electrode preparation in flexible electronic devices) technology is designed and fabricated. It consists of three main components, including polyethylene terephthalate (PET) as a flexible substrate, polyvinylidene fluoride (PVDF) piezoelectric film as a sensitive layer, and patterned electrodes printed using direct ink writing (DIW) technology. This device demonstrates the high-pressure sensing sensitivity of 51.48 μV kPa−1, a low detection limit (0.31 kPa), a fast response/recovery time of 68/102 ms, excellent cycle stability and durability. Moreover, the sensor can successfully detect body movements such as hand bending and swallowing, etc Furthermore, a 10 × 10 sensor array printed based on DIW technology is capable of perceiving and providing feedback on the spatial distribution of external pressure. The flexible pressure sensor printed based on DIW technology has great application prospects in monitoring human movement and flexible wearable electronic skin.

Additive manufacturing (AM) technology has recently seen increased utilization due to its versatility in using functional materials, offering a new pathway for next-generation conformal electronics in the smart sensor field. However, the limited availability of polymer-based ultraviolet (UV)-curable materials with enhanced piezoelectric properties necessitates the development of a tailorable process suitable for 3D printing. This paper investigates the structural, thermal, rheological, mechanical, and piezoelectric properties of a newly developed sensor resin material. The polymer resin is based on polyvinylidene fluoride (PVDF) as a matrix, mixed with constituents enabling UV curability, and boron nitride nanotubes (BNNTs) are added to form a nanocomposite resin. The results demonstrate the successful micro-scale printability of the developed polymer and nanocomposite resins using a liquid crystal display (LCD)-based 3D printer. Additionally, incorporating BNNTs into the polymer matrix enhanced the piezoelectric properties, with an increase in the voltage response by up to 50.13%. This work provides new insights for the development of 3D printable flexible sensor devices and energy harvesting systems.

Flexible piezoelectric sensors have widespread applications in the field of wearable devices and human-machine interaction technologies. However, the manufacturing of these sensors mostly relies on manual assembly, lacking efficient manufacturing processes. In this paper, the “one-step” fabrication of flexible piezoelectric sensors is achieved with a self-developed multi-component additive manufacturing composite system The sensor was designed with the electrospun PVDF functional layer, printed Ag electrode layer, and electrospun TPU encapsulation layer. The produced sensors exhibit a sensitivity of 0.04 V/N, a rapid response time of 25 ms, good breathability $(600\ \mathrm{g}/\mathrm{m}^{2}/\text{day})$, and excellent sweat resistance. This method offers a promising approach for the efficient manufacturing of breathable and sweatproof flexible piezoelectric sensors.

The following paper aims to provide the results of an innovative structural crack detection technique using printed adaptive sensors. They were manufactured using conductive ink with silver microparticles and polymer insulators. The technique leveraged the unique properties of Direct Ink Write additive manufacturing combined with domain knowledge in the field of technical condition monitoring. The goal was to achieve high sensitivity and precision in detecting fatigue-crack-induced changes in structural components. The sensors’ fabrication repeatability, output stability, and crack detection capabilities were investigated. Based on preliminary measurements of the sensors’ output characteristics, the analyzed data showed that a tolerance in the range of 5% can be obtained for batch production. Damage size estimation using this new crack gauge during a fatigue crack growth test was high compared to the reference, with less than 1 mm precision over 30 mm of crack length. Throughout the fatigue test of up to 1.5 million cycles, all CCPSs remained fully functional, with no failure-related changes in their output signal patterns. The proposed sensor has proven its reliability for the detection of fatigue cracks and propagation monitoring and is a good alternative to other SHM technologies for this purpose.

This study details the exploration of a novel PolyEtherEtherKetone (PEEK) ‐ Carbon Fiber (CF)/Carbon Nanotubes (CNT) filament designed for additive manufacturing of lattice structures with controlled thermo‐piezoresistive properties. PEEK, a semi‐crystalline thermoplastic material with excellent strength and thermal stability, exhibits enhanced electrical conductivity when paired with CNTs. The combined presence of CNT and CF allows for improved structural integrity and reliable signal responsiveness, making the PEEK‐CF/CNT composite ideal to use in additive manufacturing of high‐performance sensors. Moreover, the printing of structures with stress plateau regions such as Auxetic 3D and Truncated Octahedron lattices enables controlled temperature or force sensing. Plateau stress present at 5%–15% strain allows for the decoupling of piezoresistive and thermoresistive responses within the lattice structures with a 99.7% repeatability up to 100°C. This mechanism is crucial for applications requiring differentiated responses to mechanical and thermal stimuli, allowing the composite to selectively respond to changes in force or temperature without interference from the other variable, essential for accurate and reliable sensing in complex environments. This advancement in using PEEK‐CF/CNT composites marks a significant contribution to additive manufacturing of multifunctional composites with embedded sensing.

Nature has always inspired humans to create innovative tools. Arachnids show exceptional and functional sensory receptors at a small scale. Air flow mechanoreceptors, commonly called trichobothria, are used in different shapes and sizes by several arachnid species. The goal of this work is to develop flat hair-like sensors inspired by the adult Buthus occitanus scorpion. A sensor that responds to airflow has been developed and realized using multi-material additive manufacturing (also known as 3D printing). The sensor has been sputter coated with platinum to add piezoresistive sensing capabilities. Preliminary results with an unbalanced voltage divider show a promising response in the mV region.

Photo-mediated additive manufacturing from liquid resins (vat photopolymerization) is a rapidly growing field that will enable a new generation of electronic devices, sensors, and soft robotics. Radical-based polymerization remains the standard for photo-curing resins during the printing process due to its fast polymerization kinetics and the range of available photoinitiators. Comparatively, there are fewer examples of non-radical chemical reactions for vat photopolymerization, despite the potential for expanding the range of functional materials and devices. Herein, we demonstrate ionic liquid resins for vat photopolymerization that utilize photo-base generators (PBGs) to catalyze thiol-Michael additions as the network forming reaction. The ionic liquid increased the rate of curing, while also introducing ionic conductivity to the printed structures. Among the PBGs explored, 2-(2-nitrophenyl)-propyloxycarbonyl tetramethylguanidine (NPPOC-TMG) was the most effective for the vat photopolymerization process wherein 250 μm features were successfully printed. Lastly, we compared the mechanical properties of the PBG catalyzed thiol-Michael network versus the radical polymerized network. Interestingly, the thiol-Michael network had an overall improvement in ductility compared to the radical initiated resin, since step-growth methodologies afford more defined networks than chain growth. These ionic liquid resins for thiol-Michael additions expand the chemistries available for vat photopolymerization and present opportunities for fabricating devices such as sensors.

One important issue associated to magnetocaloric materials that hinders its technological application is the poor processability and structural integrity of those with the highest performance, usually intermetallics undergoing first‐order magnetic phase transitions. Additionally, the performance of these magnetocaloric materials highly depends on the structural stability of the magnetocaloric phase, which is, in many cases, very sensitive to temperature and mechanical processes. Additive manufacturing via the extrusion of polymer‐based composites is regarded as a promising way to overcome these issues. A recently presented manufacturing method of encapsulating functional fillers into polymer capsules has been used to produce a composite filament with a large load of magnetocaloric off‐stoichiometric Ni2MnGa Heusler alloy fillers with a uniform distribution throughout the polymer matrix as demonstrated by x‐ray tomography characterization. The incorporation of these metallic particles causes changes in the thermal behavior of the polymer as well as an increase in the flowability of the composite with respect to the polymer at the same temperature. The increased flowability of the composites found during manufacturing can be compensated by lowering the extrusion temperatures, making this technique even more convenient for preserving the filler properties, which is an important concern when additive manufacturing magnetocaloric materials. This is confirmed by the magnetic and magnetocaloric behavior of the composites, with responses proportional to the fraction of fillers. Ultrasonic‐atomization produces highly spherical Ni‐Mn‐Ga Heusler alloy particles. Ni‐Mn‐Ga filled polymer capsules allow a direct extrusion of composites for AM. X‐ray tomography shows uniform volumetric filler distribution within the filaments. Decreased viscosity of the matrix favors the lowering of the processing temperature. The low processing temperatures avoid altering the MCE of the alloy fillers.

There is a growing need to design tailored alloys for Additive Manufacturing (AM) in order to achieve the desired properties and quality in the resulting parts. The need is even stronger for functional materials such as Nickel- Titanium (NiTi) shape memory alloys (SMAs) with microstructure-driven properties such as superelasticity and the shape memory effect. These alloys have been used in innovative applications in aerospace, biomedical, and robotics. Despite their potential, the realization of NiTi SMAs through AM faces significant challenges, including phase stability, compositional heterogeneity, and solidification defects, which impede the achievement of desired microstructural and mechanical characteristics.

Micrometer-resolution 3D printing of functional oxides is of growing importance for the fabrication of micro-electromechanical systems (MEMSs) with customized 3D geometries. Compared to conventional microfabrication methods, additive manufacturing presents new opportunities for the low-cost, energy-saving, high-precision, and rapid manufacturing of electronics with complex 3D architectures. Despite these promises, methods for printable oxide inks are often hampered by challenges in achieving the printing resolution required by today's MEMS electronics and integration capabilities with various other electronic components. Here, a novel, facile ink design strategy is presented to overcome these challenges. Specifically, we first prepare a high-solid loading (∼78 wt%) colloidal suspension that contains polyethyleneimine (PEI)-coated stannic dioxide (SnO2) nanoparticles, followed by PEI desorption that is induced by nitric acid (HNO3) titration to optimize the rheological properties of the printable inks. Our achieved ∼3-5 μm printing resolution is at least an order of magnitude higher than those of other printed oxide studies employing nanoparticle ink-based printing methods demonstrated previously. Finally, various SnO2 structures were directly printed on a MEMS-based microelectrode for acetylene detection application. The gas sensitivity measurements reveal that the device performance is strongly dependent on the printed SnO2 structures. Specifically, the 3D structured SnO2 gas sensor exhibits the highest response of ∼ 29.9 to 100 ppm acetylene with the fastest total response time of ∼ 65.8 s. This work presents a general ink formulation and printing strategy for functional oxides, which further provides a pathway for the additive manufacturing of oxide-based MEMSs.

Similarly to the developments in green electronics, the emerging field of additive piezo-electronics increasingly focuses on more sustainable electroactive materials and cleaner production workflows. However, solution processing with hazardous solvents remains common, even for hybrid organic-inorganic piezoelectric materials (piezocomposites) made from eco-friendly biopolyesters polyhydroxyalkanoates, including ductile copolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)(PHBHHx). Therefore, we investigated the solvent-free extrusion-based manufacturing and fused filament fabrication (FFF) of lead-free piezoceramic-rich PHBHHx composite with 80 wt% of barium titanate (BTO). Physicochemical characterization of filaments and prints revealed favorable melt reprocessing capability of PHBHHx as both neat and BTO-rich biopolymers retained chemical structure and thermal stability after three remelting cycles (single or double extrusion at 130 °C–140 °C and FFF at 170 °C). The re-extrusion and FFF processes were calibrated to ensure consistent printability of well-homogenized and well-fused piezocomposite (0–3 connectivity). The tensile loading of neat and BTO-rich PHBHHx structures at increasing speeds revealed complex material behavior of strain-rate-dependent strengthening, weakening, hardening and softening. Despite the high BTO fraction, the composite maintained acceptable flexibility, although the tensile strength decreased due to weaker filler-matrix interfacial bonding. The piezoelectric response and stabilization (d33 decay due to initial ferroelectric depolarization) were analyzed over a wide range of poling fields and durations. The 3D-printed piezocomposite demonstrated excellent high-field poling capability up to ∼22 kV mm−1. It provided a comparatively high maximum piezoresponse of ∼11 pC/N, matching the predictions of the Jayasundere–Smith model for two-phase particulate composites. The presented sustainable and scalable melt-based workflow is accessible to the 3D printing community, supporting democratization and further advances in the material extrusion additive manufacturing of piezoelectric sensors, energy harvesters/nanogenerators and other devices. The experimental findings are useful for the development of environmentally safe melt processing routes to produce highly filled PHBHHx-based composites.

The recycling of post-industrial waste poly(lactic acid) (PI-PLA) from coffee machine pods into electroanalytical sensors for the detection of caffeine in real tea and coffee samples is reported herein. The PI-PLA is transformed into both nonconductive and conductive filaments to produce full electroanalytical cells, including additively manufactured electrodes (AMEs). The electroanalytical cell was designed utilizing separate prints for the cell body and electrodes to increase the recyclability of the system. The cell body made from nonconductive filament was able to be recycled three times before the feedstock-induced print failure. Three bespoke formulations of conductive filament were produced, with the PI-PLA (61.62 wt %), carbon black (CB, 29.60 wt %), and poly(ethylene succinate) (PES, 8.78 wt %) chosen as the most suitable for use due to its equivalent electrochemical performance, lower material cost, and improved thermal stability compared to the filaments with higher PES loading and ability to be printable. It was shown that this system could detect caffeine with a sensitivity of 0.055 ± 0.001 μA μM–1, a limit of detection of 0.23 μM, a limit of quantification of 0.76 μM, and a relative standard deviation of 3.14% after activation. Interestingly, the nonactivated 8.78% PES electrodes produced significantly better results in this regard than the activated commercial filament toward the detection of caffeine. The activated 8.78% PES electrode was shown to be able to detect the caffeine content in real and spiked Earl Grey tea and Arabica coffee samples with excellent recoveries (96.7–102%). This work reports a paradigm shift in the way AM, electrochemical research, and sustainability can synergize and feed into part of a circular economy, akin to a circular economy electrochemistry.