植入电极、器件的封装层对离子渗透的屏蔽效果

Wearable and implantable bioelectronics that can interface for extended periods with highly mobile organs and tissues across a broad pH range would be useful for various applications in basic biomedical research and clinical medicine. The encapsulation of these systems, however, presents a major challenge, as such devices require superior barrier performance against water and ion penetration in challenging pH environments while also maintaining flexibility and stretchability to match the physical properties of the surrounding tissue. Current encapsulation materials are often limited to near-neutral pH conditions, restricting their application range. In this work, we report a liquid-based encapsulation approach for bioelectronics under extreme pH environments. This approach achieves high optical transparency, stretchability, and mechanical durability. When applied to implantable wireless optoelectronic devices, our encapsulation method demonstrates outstanding water resistance in vitro, ranging from extremely acidic environments (pH = 1.5 and 4.5) to alkaline conditions (pH = 9). We also demonstrate the in vivo biocompatibility of our encapsulation approach and show that encapsulated wireless optoelectronics maintain robust operation throughout 3 months of implantation in freely moving mice. These results indicate that our encapsulation strategy has the potential to protect implantable bioelectronic devices in a wide range of research and clinical applications. Medical devices face stability challenges in extreme pH conditions. Here, the authors report a liquid-based encapsulation approach that achieves year-long encapsulation in acidic conditions

Wearable and implantable electronic (WIE) devices have found widespread applications in real-time health monitoring systems. Materials in flexible, thin film form that can serve as long-lived barriers to biofluid penetration are essential to the development of chronic biomedical implants. Ions in biofluids (such as $Na^{+}$) that diffuse through the encapsulation layer can adversely affect the performance of the entire system. In this work, we have conducted systematic theoretical simulations on the ion-diffusion behaviors of combinations of silicon oxides and nitrides. Alternating dielectric layers of $SiO_{2}/SiN_{x}/SiO_{2}$ have been proven to effectively retard ion transport compared with the single or bilayer films. Our numerical model serves as the prediction of ion diffusion induced threshold voltage shift which is the basis for lifetime projection for MOSFET-based biomedical implants.

We propose and demonstrate a comprehensive method to quantify the ultra-low permeability of thin-film encapsulation coatings engineered for bioelectronic implantable micro-devices. The method relies on the monitoring of the corrosion of magnesium (Mg) thin-film integrated in resistive sensors, on rigid, flexible and stretchable substrates. Corrosion in the Mg film is induced by water diffusion through the coating and is analysed in terms of the evolving electrical resistance; the corrosion rate can next be correlated with the barrier properties, (i.e., the water vapour transmission rate, WVTR) of the encapsulation coating. The ultra-high sensitivity (3.3×10-8 g/m2/day at room temperature) that is achieved with this method is unmet and particularly suitable for ultrathin ultra-high barrier encapsulations of bioelectronic implants. The sensing method is next demonstrated in flexible and stretchable microsystems where the Mg monitoring sensor is integrated into an optimized and reliable microfabrication process.

No abstract available

Reliable long‐term function is crucial for flexible and soft bioelectronics. Mechanical defects and permeation of water molecules across the various device layers are the prime drivers of failure, and particularly in applications requiring continuous contact with biofluids (i.e. for implantable applications). To address demanding needs of miniaturization, mechanical compliance and water impermeability, ultra‐thin high‐barrier encapsulations are a promising way to improve device reliability. In this work, the encapsulation properties of vapour phase infiltration (VPI) of inorganic Al2O3 layers deposited by atomic layer deposition (ALD), as bilayers with TiO2, onto polyimide and parylene C organic substrates are investigated. The layers are grown in a single reactor and the infiltration is performed in a single process, with a resulting nanometric infiltration depth. Mechanical integrity and hermeticity are characterized through tensile fragmentation tests and accelerated aging tests. Flexible Magnesium sensors monitor water vapor permeability in situ. A remarkable improvement in the crack onset strain (∽2.56 times), interfacial shear strength (∽2.1 times), water vapour transmission rate (∽5.2 times) and lifetime performance (∽7.1 times) is achieved, compared to the non‐infiltrated ALD coatings. Pluri‐infiltrated multilayers are proposed as alternatives to conventional coatings. This work is envisioned to accelerate research progress on hermetic packaging of flexible bioelectronics.

This study comprehensively examines the barrier properties, aging behavior, and failure mechanisms of Parylene F-VT4 films, applied at four distinct thicknesses (0.3 µm, 0.6 µm, 0.9 µm, and 1.2 µm), as encapsulation layers for implantable medical devices. Parylene F-VT4, a fluorinated polymer known for its mechanical flexibility, thermal stability, and chemical inertness, is a promising candidate for long-term hermetic encapsulation. Parylene F-VT4 was uniformly deposited via a dedicated chemical vapor deposition (CVD) process typically used for Parylene depositions. The investigation of the Parylene F-VT4 films included pinhole density characterization, electrochemical impedance spectroscopy (EIS), and testing of coating lifetime based on the resistance of Cu meanders protected by Parylene F-VT4 when immersed in phosphate-buffered saline (PBS) under accelerated aging conditions (PBS at 60 °C) over 550 days. The EIS results demonstrated that thicker coatings (1.2 µm) exhibited excellent barrier properties and resistance to electrolyte penetration, whereas thinner coatings (0.3 µm and 0.6 µm) showed more rapid degradation due to microvoids and pinholes. The temporal evaluation of EIS spectra highlighted the gradual decrease in impedance magnitude, indicating the ingress of ions and water into the coating. The lifetime in PBS at 60 °C was determined by resistance-based lifetime measurements on Cu meander structures coated with Parylene F-VT4 coatings. The lifetime at 37 °C was calculated, assuming an acceleration factor of 2 per 10 °C increase in temperature, yielding lifetimes of approximately 25 days, 6.4 months, 2.3 years, and 4.5 years for 0.3 µm, 0.6 µm, 0.9 µm, and 1.2 µm coatings, respectively. These findings highlight the critical relationship between thickness and durability, providing valuable insights into the long-term performance of thin Parylene F-VT4 films for implantable devices.

With the increasing demand for advanced biomedical technologies, there is a pressing need for flexible, integrated systems capable of simultaneously detecting and stimulating biological processes with high precision and reliability. In this study, an on‐chip integrated flexible electronic system is successfully fabricated that combines both photoelectric detection and stimulation functionalities. This system integrates single‐crystal silicon nanomembrane (Si‐NM) photodiode array with micro‐all‐inorganic light‐emitting diodes (µ‐ILEDs), achieving comprehensive flexibility and complete encapsulation. The Si‐NM photodiode exhibits broad responsivity across the visible light spectrum. Observed spatial response variations enable the detector array to accurately capture spatial information, precisely determining the position and direction of the light sources. Notably, the system incorporates an ultrathin thermally grown silicon dioxide (t‐SiO2) biofluid barrier. This barrier ensures stable leakage current in the device following 120 h of immersion in 90 °C PBS solution, guaranteeing long‐term stability and reliability. Furthermore, this barrier effectively prevents the infiltration of toxic elements into surrounding tissues, ensuring the safety and biocompatibility of the implant. By leveraging advanced materials and manufacturing technologies, this system not only enhances the performance of optoelectronic devices but also expands their application scope in the biomedical field, opening new avenues for future biomedical research and clinical innovations.

Implantable bioelectronic devices, due to their prolonged contact with biological tissues, face persistent challenges including moisture permeation, mechanical deformation, and biofouling. Traditional encapsulation strategies using either inorganic or organic materials face trade-offs between moisture barrier performance and mechanical flexibility. Inorganic materials provide excellent moisture resistance but are brittle, whereas organic polymers are flexible but inherently permeable. Here, we developed a Multi-layered Organic-based Liquid Encapsulation (MOLE) specifically tailored for implantable bioelectronics. MOLE consists of a layer-by-layer assembly of amine-functionalized silicone elastomer and Parylene-C, forming chemically bonded and conformal interfaces with enhanced interfacial adhesion. The outermost silicone layer, infused with silicone oil, minimizes protein adsorption (<1%), resists biofilm formation (sliding angle <10°), and prevents adhesion of inflammatory cells and proteins, thereby reducing acute inflammation. This hybrid architecture achieves an 86-fold improvement in adhesion strength compared to conventional Parylene-C coatings and significantly enhances mechanical robustness under dynamic deformation. In addition, MOLE provides superior moisture and ion barrier properties. Accelerated aging tests at 85°C demonstrated a 160-fold increase in insulation lifetime over Parylene-C, equivalent to approximately 445 h at physiological temperature (37°C). Furthermore, in vivo studies using a degradable magnesium antenna demonstrated stable encapsulation, minimal interfacial disruption, and strong resistance to biological degradation over time.

Implantable strain sensors integrated on organ surfaces can monitor organ deformations, such as bladder filling and stomach motility, thereby providing important information about their functional states. A major challenge lies in achieving large strain ranges while ensuring biocompatibility and long-term stability inside physiological fluid environments. Commonly used stretchable materials have relatively high water permeability, which can lead to degradation of sensing performance. This work presents a method to provide highly stretchable, biocompatible, compliant, and stable encapsulation for implantable capacitive strain sensors. Conformal deposition of parylene, a widely used encapsulation material with limited stretchability, followed by controlled mechanical buckling, creates microscale wrinkles in the parylene coating. A thermal annealing step reduces Young's modulus of parylene, which converts globally buckled thick (>5 μm) parylene coating into microscale wrinkles. This simple annealing step effectively enhances the stretchability and barrier properties of the parylene coating. The resulting biocompatible wrinkled parylene encapsulation provides over 60% mechanical stretchability and a normalized water vapor transmission rate of 0.07 g mm/m2/day, offering one of the best combinations of barrier properties and stretchability among different encapsulation materials. In addition, the uniaxially microwrinkled encapsulation results in a more than doubled gauge factor for capacitive strain sensing by suppressing the Poisson effect. Thermally accelerated dynamic testing of encapsulated strain sensors validates their long-term stability. Additionally, strain sensing using encapsulated sensors sutured on a bladder phantom and ex vivo porcine bladders demonstrates their potential for real-time organ deformation sensing. The versatility of this encapsulation method makes it promising for a wide variety of stretchable implantable devices, supporting continuous organ monitoring and targeted therapy.

Encapsulation materials play an important role in many applications including wearable electronics, medical devices, underwater robotics, marine skin tagging system, food packaging, and energy conversation and storage devices. To date, all the encapsulation materials, including polymer layers and inorganic materials, are solid materials. These solid materials suffer from limited barrier lifetimes due to pinholes, cracks, and nanopores or from complicated fabrication processes and limited stretchability for interfacing with complex 3D surfaces. This paper reports a solution to this material challenge by demonstrating bioinspired oil-infused slippery surfaces with excellent waterproof property for the first time. A water vapor transmission test shows that locking a thin layer of oil on the silicone elastomer improves the water vapor barrier performance by three orders of magnitude. Accelerated lifetime tests suggest robust water barrier characteristics that approach 226 days at 37 °C even under severe mechanical damage. A combination of temperature- and thickness-dependent experimental measurements and reaction-diffusion modeling reveals the key waterproof property. In addition to serving as a barrier to water, the oil-infused surface demonstrates an attractive ion barrier property. All these exceptional properties suggest the potential applications of slippery surfaces as encapsulation materials for medical devices, underwater electronics, and many others.

No abstract available

Biodegradable polymers have been employed as encapsulants for transient, resorbable implantable devices due to moderate water permeability, mechanical flexibility, and biocompatibility, however most of them relatively lack inherent anti‐biofouling properties. This limitation can lead to undesired protein adsorption, cell adhesion, and fibrotic encapsulation, compromising device function and biocompatibility, particularly for long‐term implantation scenarios. Here, this study introduces a soft, stretchable, and anti‐biofouling encapsulant engineered by integrating self‐assembled organosilicon nanowire networks onto micropatterned biodegradable elastomers. The resulting hierarchical surface architecture imparts superhydrophobicity while preserving mechanical integrity, improving water barrier performance by up to 420% compared to unmodified films and retaining stability under cyclic strains. Integration into a transient, stretchable optoelectronic device enables prolonged operation in aqueous environments, and in vitro and in vivo evaluations demonstrate suppressed cell adhesion, reduced fibrotic tissue formation, and excellent biocompatibility, highlighting the potential for long‐lasting, bioresorbable electronic implants.

Long-term bioelectronic implants require stable, hermetic encapsulation. Water and ion ingress are challenging to quantify, especially in miniaturized microsystems and over time. We propose a wireless and battery-free flexible platform leveraging backscatter communication and magnesium (Mg)-based microsensors. Water permeation through the encapsulation induces corrosion of the Mg resistive sensor thereby shifting the oscillation frequency of the sensing circuit. Experimental in vitro and in-tissue characterization provides information on the operation of the platform and demonstrates the robustness and accuracy of this promising method, revealing its significance for in-situ real-time monitoring of implanted bioelectronics. Water and ion ingress are challenging to quantify, especially in miniaturized microsystems. Here, Mariello et al. report a wireless and battery-free flexible water-permeation sensing platform, using backscatter communication and Mg-based microsensors for in-situ monitoring of implantable bioelectronics.

No abstract available

In this paper, we investigate the long-term adhesion strength and barrier property of our recently proposed encapsulation stack that includes PDMS-Parylene C and PECVD interlayers (SiO2 and SiC) for adhesion improvement. To evaluate the adhesion strength of our proposed stack, the sample preparation consisted in depositing approximately 25 nm of SiC and 25 nm of SiO2 on half wafers, previously coated with Parylene C. Next, $50 \mu \mathrm{m}$ PDMS was spin-coated on top. Finally, the samples were detached from the Si wafer and soaked in a PBS solution at 67°C to accelerate the aging process. Two samples were also implanted, subcutaneously, on the left and right subscapular regions of a rat. The optical inspection and peel tests performed after two months confirmed our preliminary findings and showed a significant improvement of the adhesion in our proposed encapsulation stack compared to the case of PDMS on Parylene C alone. In addition, the X-ray photoelectron spectroscopy(XPS) analysis at the interface between SiC and Parylene C showed different peaks for the interface compared to the reference spectra, which could be an indication of a chemical bond. Finally, water vapor transmission rate (WVTR) tests were performed to investigate the barrier property of our proposed encapsulation stack against water vapor transmission. The results demonstrated that the proposed stack acts as a significantly (two orders of magnitude) higher barrier against moisture compared to only Parylene C and PDMS encapsulation layers. The proposed method yields a fully transparent encapsulation stack over a broad wavelength spectrum that can be used for the conformal encapsulation of flexible devices and thus, making them compatible with techniques such as optical imaging and optogenetics.

Ionic polymer–metal composites, although with attracting properties such as flexibility, easy processing, resilience, and high sensitivity, have some drawbacks including the fragility of electrodes and strong humidity dependence which limit their practical applications. This study aims to fabricate ionic polymer–metal composites with sputtered gold thin film electrodes and to coat them with a waterproof acrylic material to extend their consistent sensory response over time. For this aim, after explaining the sensing mechanism of ionic polymer–metal composites based on streaming potential hypothesis for compression, bending, and shear modes, the fabrication process of the proposed ionic polymer–metal composites is presented. A signal conditioner is designed based on the measurement results of the equivalent resistance and capacitance of the devices. A shock tube setup is then utilized to obtain the impulse response of fabricated ionic polymer–metal composite devices in different modes of deformation. To verify how this waterproof coating maintains the ionic polymer–metal composite’s sensing performance, some experiments are carried out over a period of 6 days after fabrication for both acrylic-coated and uncoated samples. Analyzing the results shows that fabricated ionic polymer–metal composites represent an appropriate linearity, sensitivity, and reliability over time and this coating approach not only suppresses the diluent permeation but also has a negligible effect on the ionic polymer–metal composite electromechanical properties.

No abstract available

Titanium and its alloys are widely used in biomedical implants due to their favorable mechanical properties and corrosion resistance; however, their natural surface lacks sufficient bioactivity and antibacterial performance. Micro-arc oxidation is a promising approach to producing bioactive coatings, and the incorporation of nanoparticles such as TiO2 may further improve their functionality. This study aimed to determine the optimal TiO2 nanoparticle concentration in the micro-arc oxidation electrolyte that ensures coating stability and biological safety. Calcium–phosphate coatings were fabricated on commercially pure titanium using micro-arc oxidation with two TiO2 concentrations: 0.5 wt.% (MAO 1) and 1 wt.% (MAO 2). Surface morphology, porosity, and phase composition were analyzed by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. Corrosion resistance was evaluated via potentiodynamic polarization in NaCl and Ringer’s solutions, while biocompatibility was assessed in vitro using HOS human osteosarcoma cells and MTT assays. Increasing the TiO2 content to 1% decreased coating porosity (13.7% vs. 26.3% for MAO 1), enhanced corrosion protection, and reduced the friction coefficient compared to bare titanium. However, MAO 2 exhibited high cytotoxicity (81% cell death) and partial structural degradation in the biological medium. MAO 1 maintained integrity and showed no toxic effects (3% cell death). These results suggest that 0.5% TiO2 is the optimal concentration, providing a balance between corrosion resistance, mechanical stability, and biocompatibility, supporting the development of safer implant coatings.

In this study, we prepared a silicon-containing electrolyte solution and a silicon-containing titanium dioxide coating (Si–TiO2) on the surface of medical titanium by way of microarc oxidation. The surface properties of the formed Si–TiO2 were evaluated using field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction (XRD), and a profilometer. The corrosion resistance of Si–TiO2 was evaluated by way of an electrochemical workstation. The biocompatibility and biological activity of Si–TiO2 were evaluated using in vitro cell culture. The results indicated that Si–TiO2 could be successfully deposited on the surface of titanium using microarc oxidation, and XRD confirmed that the Si–TiO2 was mainly composed of titanium dioxide. The Nyquist curve and Tafel curve indicated that the surface Si–TiO2 improved the corrosion resistance of titanium. In vitro cell experiments confirmed that Si–TiO2 promoted the adhesion and proliferation of the MC3T3-E1 cells. In conclusion, microarc oxidation could be used to introduce silicon onto the surface of titanium implants, and this porous surface not only improved the wear and corrosion resistance of titanium but also had good biological activity. Thus, the use of Si–TiO2 on titanium implants warrants further research for potential clinical applications.

In this work, we demonstrate that the permeability of a SiNx thin film (prepared by plasma-enhanced chemical vapor deposition) to water and oxygen is closely related to the deposition pressure. By dynamic secondary ion mass spectrometry, we confirmed that water penetration occurs into the SiNx film only in the oxidized layer. Furthermore, positron annihilation lifetime spectroscopy indicated that a SiNx film with a lower deposition pressure provides a smaller pore (free volume hole) radius, which is more effective in terms of blocking ambient molecular diffusion or penetration. The SiNx films were also applied as an encapsulation layer for organic light-emitting diodes; SiNx films with a lower deposition pressure exhibited higher encapsulation properties.

In-depth understanding of lithium (Li) diffusion barriers is a crucial factor for enabling Li-ion based devices like 3D thin-film batteries and synaptic redox transistors integrated on silicon substrates. Diffusion of Li-ions into the silicon can damage surrounding components, detach the device itself, lead to battery capacity loss, and cause uncontrolled change of the transistor channel conductance. In this study, we analyze for the first time ultrathin 10 nm titanium nitride (TiN) films as bifunctional Li-ion diffusion barrier and current collector. Thermal atomic layer deposition (ALD) and pulsed chemical vapor deposition (pCVD) are employed for manufacturing. 10 nm ALD films demonstrate excellent blocking capability with an insertion of only 0.03 Li per TiN formula unit exceeding 200 galvanostatic cycles at 3 µA/cm2 between 0.05 and 3 V vs. Li/Li+. An ultra-low electrical resistivity of 115 µΩ cm is obtained. In contrast, a partial barrier breakdown is observed for 10 nm pCVD films. High surface quality with low contamination is identified as a key factor for the excellent performance of ALD TiN. Conformal deposition of 10 nm ALD TiN in 3D structures with high aspect ratios of up to 20:1 is demonstrated. The measured capacities of the surface area enhanced samples are in good agreement with the expected values. High-temperature blocking capability is proven for a typical electrode crystallization step. Ultrathin ALD TiN is an ideal candidate as an electrically conducting Li-ion diffusion barrier for Si-integrated devices.

No abstract available

Ni‐rich Li(Ni1−x−yMnxCoy)O2 (NMC) is an attractive cathode material for Li‐ion batteries due to its high practical capacity (>200 mAh g−1). However, it is plagued by stability issues that, over multiple cycles or prolonged storage in air, degrade the material and decreases its electrochemical performance. A thin‐film model system can be used to simplify the cathode by omitting all passive components and electrode porosity and allow for an in‐depth analysis on the interfacial reactions that initiate the material degradation. In this work, the reactions occurring during the fabrication of thin film NMC are investigated. A lot of these reactions stemmed from the loss of active material from the film toward the substrate during annealing. Methods are then devised to reduce the unwanted reactions occurring during annealing. These included lowering the annealing temperature, compensating for material loss, as well as depositing a diffusion barrier between the substrate and NMC film. The findings in this paper outline the various conditions that affect the preparation of thin‐film NMC and give readers an overview of reactions to consider when developing thin‐film battery materials.

Abstract Miniaturization of next‐generation active neural implants requires novel micro‐packaging solutions that can maintain their long‐term coating performance in the body. This work presents two thin‐film coatings and evaluates their biostability and in vivo performance over a 7‐month animal study. To evaluate the coatings on representative surfaces, two silicon microchips with different surface microtopography are used. Microchips are coated with either a ≈100 nm thick inorganic hafnium‐based multilayer deposited via atomic layer deposition (ALD‐ML), or a ≈6 µm thick hybrid organic–inorganic Parylene C and titanium‐based ALD multilayer stack (ParC‐ALD‐ML). After 7 months of direct exposure to the body environment, the multilayer coatings are evaluated using optical and cross‐sectional scanning electron microscopy. Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) is also used to evaluate the chemical stability and barrier performance of the layers after long‐term exposure to body media. Results showed the excellent biostability of the 100 nm ALD‐ML coating with no ionic penetration within the layer. For the ParC‐ALD‐ML, concurrent surface degradation and ion ingress are detected within the top ≈70 nm of the outer Parylene C layer. The results and evaluation techniques presented here can enable future material selection, packaging, and analysis, enhancing the functional stability of future chip‐embedded neural implants.

Poly(chloro-p-xylylene) (parylene C) is recognized for its outstanding chemical resistance, high thermal stability, biocompatibility, and superior permeability barrier properties. This material predominantly exists in a semicrystalline state. Despite its significance, theoretical studies simulating the semicrystalline parylene C system are scarce. This study aims to elucidate the relationship between the semicrystalline structures and the barrier properties of parylene C through a molecular dynamics approach. Semicrystalline parylene C with 10-50% aligned regions were constructed, which exhibited a degree of crystallinity ranging from 17% to 44%. We discovered that increased aligned chains could significantly alter the material's structure and morphology. These changes could further lead to variations in the density, fractional free volume, and pore size distribution of parylene C, thus affecting its glass transition temperature, permeability barrier and mechanical properties. Additionally, the relative values of gas permeability coefficients closely match experimental data. The insights into the structure-property relationship presented in this work could offer valuable guidance for developing functionalized and structured parylene C as coating materials.

Parylene C is a widely used dielectric barrier in implantable medical devices because it conforms well to surfaces and insulates against biological environments. However, multiple studies have shown that moisture can intrude into Parylene C films through defects and intrinsic diffusion, leading to delamination and device failure. While many studies have tested device integrity in vitro, few have isolated the influence of specific degradation mechanisms on device failure. Here, we use a broadband impedance technique called Microwave Microfluidic Spectroscopy (MMS) to measure fluid permeation in targeted regions of Parylene C films that are free of defects and have optimal adhesion to the substrate. We found no changes in the broadband S-parameters from 100 MHz–110 GHz for Parylene C coated coplanar waveguides soaked in water or phosphate buffered saline at 20 °C or 37 °C for two months. Furthermore, there was no delamination induced by fluid soaking. Our study helps to clear debate about the influence of water and ion diffusion on Parylene C device lifetime and inform better fabrication of Parylene C coatings for implantable devices.

The polymer family of Parylene is a promising candidate for the realization of smart systems due to its unique combination of excellent properties. These particularly include compatibility to most established microtechnologies, but also barrier properties enabling its use as encapsulation layer. Additionally, some Parylene types are classified to be biocompatible according ISO 10993, so that they can be used for medical applications such as medical implants. The presented paper aims to investigate the biocompatibility of Parylene F, which is not certified to be biocompatible but of high interest for technical use due to its better thermal stability compared to the more common Parylene C. Furthermore, the literature reports the diffusion of toxic metal ions through Parylene C. With respect to the use of Parylene as a biocompatible encapsulation layer for medical implants, this paper investigates, whether Parylene C is suitable to encapsulate a cytotoxic copper layer and avoid diffusion, particularly for the combination of Parylene C with inorganic metal oxide layers to form an ultrabarrier. For both investigations, cytotoxicity tests according to ISO 10993–5 were performed. The results prove the same cell behavior of Parylene F compared to the biocompatible certified Parylene C as well as the suppression of the diffusion of toxic metal ions through Parylene C and Parylene based ultrabarriers.

No abstract available

Electrolyte-gated carbon nanotube field-effect transistors (EG-CNTFETs) are a promising bio-sensing platform, but the instability of carbon nanotubes (CNTs), e.g., high leakage current and hysteresis, remains a major limitation. In this paper, we demonstrate that incorporating a lipophilic membrane on the semiconducting channel reduces the EG-CNTFET stabilization time to 34 minutes compared to an hour for state-of-the-art devices. Moreover, the on-off ratio of the devices improves over time (9.76 ± 4.16 to 24.55 ± 20.99), whereas the on-off ratio of devices without the membrane decreases (88.7 ± 29.9 to 61.1 ± 23.9). As proof-of-concept, the encapsulated devices were functionalized with an ion-selective membrane for detecting ammonium ion. The calibration curve showed a linear detection range from 0.01 mM to 100 mM with a coefficient of determination of 94.71%, and a sensitivity of 0.143 μA/decade.

Organic-inorganic hybrid perovskites have shown tremendous potential for optoelectronic applications. Ion migration within the crystal and across heterointerfaces, however, imposed severe problems with material degradation and performance loss in devices. Encapsulating hybrid perovskite with a thin physical barrier can be essential for suppressing the undesirable interfacial reactions without inhibiting the desirable transport of charge carriers. Here, we demonstrated that nanoscale, pinhole-free Al2O3 layer can be coated directly on the perovskite CH3NH3PbI3 using atomic layer deposition (ALD). The success can be attributed to a multitude of strategies including surface molecular modification and hybrid ALD processing combining the thermal and plasma-enhanced modes. The Al2O3 films provided remarkable protection to the underlying perovskite films, surviving by hours in solvents without noticeable decays in either structural or optical properties. The results advanced the understanding of applying ALD directly on hybrid perovskite and provided new opportunities to implement stable and high-performance devices based on the perovskites.

In this paper, we have investigated the effectiveness of atomic layer deposition (ALD) of Al2O3 as a passivation for wafer scale integration on the silicon interconnect fabric (Si-IF). Due to high conformality and quality of ALD thin films, this deposition technique is gaining more applications in microelectronics fabrication. Humidity testing was utilized to evaluate barrier properties of Al2O3 for different thicknesses (10 to 17 nm). XRD analysis was used to identify oxide formation in blanket copper samples passivated with Al2O3. We have concluded that thin films with thicknesses above 10 nm can efficiently protect Cu from oxidation under standard humidity exposure conditions. To study the conformality of the film on bonded samples, focused ion beam (FIB) and SEM imaging were performed. Thickness of the film remained constant from the top surface of the bonded die all the way down to the interface of the die and substrate. To further analyze the robustness of Al2O3 films in protecting Cu interconnects from oxidation, bonded and passivated samples were exposed to humidity testing for 216 hours and the variation in electrical resistance of the samples before and after the testing was less than 5%.Finite element analysis was utilized to study residual thermal stresses in samples with and without passivation as well as the effect of the passivation material on residual stresses. Adding passivation layer increases compressive residual stresses within Cu pillar. However, in case of the bilayer passivation (Parylene C/SiNx); high tensile residual stress at the interface of the two thin films may adversely affect the barrier properties.

Objective. Ensuring the longevity of implantable devices is critical for their clinical usefulness. This is commonly achieved by hermetically sealing the sensitive electronics in a water impermeable housing, however, this method limits miniaturisation. Alternatively, silicone encapsulation has demonstrated long-term protection of implanted thick-film electronic devices. However, much of the current conformal packaging research is focused on more rigid coatings, such as parylene, liquid crystal polymers and novel inorganic layers. Here, we consider the potential of silicone to protect implants using thin-film technology with features 33 times smaller than thick-film counterparts. Approach. Aluminium interdigitated comb structures under plasma-enhanced chemical vapour deposited passivation (SiO x , SiO x N y , SiO x N y + SiC) were encapsulated in medical grade silicones, with a total of six passivation/silicone combinations. Samples were aged in phosphate-buffered saline at 67 ∘C for up to 694 days under a continuous ±5 V biphasic waveform. Periodic electrochemical impedance spectroscopy measurements monitored for leakage currents and degradation of the metal traces. Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, focused-ion-beam and scanning-electron- microscopy were employed to determine any encapsulation material changes. Main results. No silicone delamination, passivation dissolution, or metal corrosion was observed during ageing. Impedances greater than 100 GΩ were maintained between the aluminium tracks for silicone encapsulation over SiO x N y and SiC passivations. For these samples the only observed failure mode was open-circuit wire bonds. In contrast, progressive hydration of the SiO x caused its resistance to decrease by an order of magnitude. Significance. These results demonstrate silicone encapsulation offers excellent protection to thin-film conducting tracks when combined with appropriate inorganic thin films. This conclusion corresponds to previous reliability studies of silicone encapsulation in aqueous environments, but with a larger sample size. Therefore, we believe silicone encapsulation to be a realistic means of providing long-term protection for the circuits of implanted electronic medical devices.

This study is motivated by the demand for advanced neuroelectronic flexible polymer-based implants in medical technology. Using a 200 mm wafer-level packaging (WLP) line, the research produces implants with biocompatible polymers, an application-specific integrated circuit (ASIC), high-performing neural electrode materials and barrier layers of Al2O3 and Parylene for moisture protection, all seamlessly incorporated into a single hermetically packaged system, ensuring both functionality and reliability in a compact design. The methodology employs fine gold lines ($10 \mu ~\mathrm{m}$) and small vias for high routing density, alongside nanoporous graphene electrodes that provide high-performance bidirectional neural interfacing. A low-temperature bonding process assembles an ASIC onto the flexible substrate, utilizing nanoporous gold pads. Key findings demonstrate the potential for large, flexible sealed devices, with prototypes up to 7 cm, paving the way for advancements in microfabricated brain implant technologies and improved patient outcomes in neurological conditions like Parkinson's disease.

Thin-film electrode arrays play an important role when large integration densities of stimulating or recording channels are required in neural interfaces. To fabricate such ultra-light-weighted and flexible implantable neural electrodes, polyimide (PI) has been used successfully as substrate and insulation material. Advantages are that PI can be processed in a standard cleanroom facility, its high chemical resistance and low moisture uptake. The disadvantage is that it allows the PI surface to come in contact with various contaminants from the photolithography steps as well as desorbed impurities from process chambers. This can lead to delamination of the PI to subsequent deposited layers. In this study, PI film surfaces were treated with oxygen (O2) plasma in reactive ion etching (RIE) and plasma enhanced chemical vapor deposition (PECVD) chambers to remove residues and activate the surface by functional groups. Results obtained from various surface analysis techniques have revealed that an O2-plasma recipe developed in the PECVD machine could replace the standard recipe in RIE. The developed O2-plasma recipe in PECVD comes with the advantage that batch processing of the wafers during plasma treatment is possible which includes processing of five 4" size wafers at once compared to the one wafer process in RIE. In both cases, hydrophobic recovery starts after six, respectively seven hours giving enough time initiating subsequent layer depositions.

Significance A critical challenge for flexible biomedical implants is in the development of materials and structures that enable intimate coupling to biotissues with long-term stability. The results presented here address this problem through a materials and integration strategy that combines highly doped silicon nanomembranes chemically bonded to thin films of thermal silicon dioxide in a construct that simultaneously serves as a biofluid barrier and a conductively coupled biointerface. Use of this approach with various flexible electronic systems, including passive and active electrodes for electrophysiological sensing and electrical stimulation, illustrate capabilities in high-fidelity operation. Systematic accelerated lifetime studies in artificial biofluids highlight the stability of these systems for chronic operation, without electrical leakage or other forms of degradation. Materials and structures that enable long-term, intimate coupling of flexible electronic devices to biological systems are critically important to the development of advanced biomedical implants for biological research and for clinical medicine. By comparison with simple interfaces based on arrays of passive electrodes, the active electronics in such systems provide powerful and sometimes essential levels of functionality; they also demand long-lived, perfect biofluid barriers to prevent corrosive degradation of the active materials and electrical damage to the adjacent tissues. Recent reports describe strategies that enable relevant capabilities in flexible electronic systems, but only for capacitively coupled interfaces. Here, we introduce schemes that exploit patterns of highly doped silicon nanomembranes chemically bonded to thin, thermally grown layers of SiO2 as leakage-free, chronically stable, conductively coupled interfaces. The results can naturally support high-performance, flexible silicon electronic systems capable of amplified sensing and active matrix multiplexing in biopotential recording and in stimulation via Faradaic charge injection. Systematic in vitro studies highlight key considerations in the materials science and the electrical designs for high-fidelity, chronic operation. The results provide a versatile route to biointegrated forms of flexible electronics that can incorporate the most advanced silicon device technologies with broad applications in electrical interfaces to the brain and to other organ systems.

The stability of long‐term microfabricated implants is hindered by the presence of multiple water diffusion paths within artificially patterned thin‐film encapsulations. Side permeation, defined as infiltration of molecules through the lateral surface of the thin structure, becomes increasingly critical with the trend of developing high‐density and miniaturized neural electrodes. However, current permeability measurement methods do not account for side permeation accurately nor quantitatively. Here, a novel optical, magnesium (Mg)‐based method is proposed to quantify the side water transmission rate (SWTR) through thin film encapsulation and validate the approach using micrometric polyimide (PI) and polyimide‐silicon carbide (PI‐SiC) multilayers. Through computed digital grayscale images collected with corroding Mg film microcells coated with the thin encapsulation, side and surface WTRs are quantified. A 4.5‐fold ratio between side and surface permeation is observed, highlighting the crucial role of the PI–PI interface in lateral diffusion. Universal guidelines for the design of flexible, hermetic neural interfaces are proposed. Increasing encapsulation's width (interelectrode spacing), creating stronger interfacial interactions, and integrating high‐barrier interlayers such as SiC significantly enhance the lateral hermeticity.

Bioresorbable electronic devices as temporary biomedical implants represent an emerging class of technology relevant to a range of patient conditions currently addressed with technologies that require surgical explantation after a desired period of use. Obtaining reliable performance and favorable degradation behavior demands materials that can serve as biofluid barriers in encapsulating structures that avoid premature degradation of active electronic components. Here, this work presents a materials design that addresses this need, with properties in water impermeability, mechanical flexibility, and processability that are superior to alternatives. The approach uses multilayer assemblies of alternating films of polyanhydride and silicon oxynitride formed by spin‐coating and plasma‐enhanced chemical vapor deposition , respectively. Experimental and theoretical studies investigate the effects of material composition and multilayer structure on water barrier performance, water distribution, and degradation behavior. Demonstrations with inductor‐capacitor circuits, wireless power transfer systems, and wireless optoelectronic devices illustrate the performance of this materials system as a bioresorbable encapsulating structure.

Effective encapsulation is essential for reliable operation of bio‐integrated electronics, particularly those containing dissolvable elements, under humid environments for desired periods of time; however, conventional inorganic or organic encapsulants often suffer from tissue‐incompatible mechanical rigidity and insufficient water‐barrier performance. Here, a mechanically resilient and efficient encapsulation strategy is proposed that can exceed a functional lifetime of state‐of‐the‐art soft encapsulations by several tens of magnitudes. The exceptional protection arises from the high aspect ratio of dissolvable yet impermeable inorganic fillers embedded within biodegradable polymers, which significantly extend the diffusion length of biofluids or water components. Theoretical modeling and experimental analysis elucidate the effects of types, shapes, and concentrations of the fillers on encapsulation performance, as well as mechanical/physical properties. The operation of electronic components under aqueous solutions for prolonged periods demonstrates the practical feasibility of the encapsulation approach for versatile types of soft, biodegradable electronics.