High Elongation at Break at Failure as a Prerequisite for Good Flexibility

In the development of the next-generation safe solid-state supercapacitors with high energy density, durability, and flexibility, the synthesis of high ion conducting solid-state polymer electrolyt...

Abstract Bacterial thermoplastic polyesters poly (3-hydroxyalkanoate) PHAs are produced by the fermentation of renewable materials, such as sugars or molasses. The pure homopolymer, PHB, and pure copolymer (3-HBP-CO-HV) (88:12) are brittle materials. PHB or PHB/V are mixed with other biodegradable materials to improve their mechanical properties. The aim is to develop biodegradable polymers of PHB-base with improved mechanical properties, such as fracture stress (27–18 MPa), strain (400–660%), impact strength and long-term stability, and to compare them with PE, PP and PET. When nucleating agents are added, smaller spherulites are formed, thus improving the mechanical properties. The mechanical properties of PHB and its blends are related to processing conditions, morphology, crystallinity and glass transition. The blends are ductile polymers with plastic deformation (necking). They are biodegraded in aerobic tests, under compost conditions in soil and water, and many pores are to be found on the surface. The blends are degraded more easily in the aerobic test, i.e. in the river water and compost, than in the soil.

… Films prepared by casting were flexible and … elongation at break with similar tensile strength (P<0.05), as can be seen in Fig. 2. Furthermore, results showed that the elongation at break …

High-strength biodegradable polymer composites have potential applications in a variety of biomedical applications. This study investigates the influence of silk fiber on the properties of the commonly used biodegradable polylactic acid-based composites, focusing on mechanical, rheological, morphological, and degradation characteristics. Mechanical tests revealed that the addition of 2.5 wt% silk fibers enhanced the ductility of PLA composites, increasing tensile strain at break from 7.39% for pure PLA to 11.51% for the composite. However, higher silk contents (≥10 wt%) resulted in lower elongation at breaks but higher moduli, indicating a trade-off between flexibility and the structural rigidity of the composite. Rheological tests demonstrated that the presence of silk fibers up to 7.5% improved the storage modulus, reflecting better network formation within the PLA matrix. Scanning Electron Microscopy (SEM) photomicrographs illustrated improved fiber dispersion, while higher contents introduced voids and stress concentrations, adversely affecting mechanical properties. Degradation tests in phosphate-buffered saline at 37 °C showed that silk additions slowed PLA degradation, suggesting controlled degradation suitable for biomedical applications. The optimal silk fiber content for balancing mechanical integrity and flexibility was identified to be ca 7.5 wt%, providing insights into the design of PLA/silk composites for enhanced performance in practical applications.

Segmented thermoplastic polyurethanes (PUs) were synthetized using macrodiols with different functional groups (carbonate, ester, and /or ether) as a segment with a molar mass of 1000 and 2000 g/mol, and 4,4’-diphenylmethane diisocyanate (MDI) and 1,4-butanediol as a rigid segment. The polyurethanes obtained reveal a wide variation of microphase separation degree that is correlated with mechanical properties and retention of tensile properties under degradation by heat, oil, weather, and water. Different techniques such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR), and synchrotron small-angle X-ray scattering (SAXS) were used to determine rigid-flexible segments’ phase behaviour. Retention of tensile properties determines the stability of the samples under different external factors. This work reveals that pure polycarbonate-based macrodiols induce the highest degree of phase miscibility, better tensile properties, hardness shore A, and retention of tensile properties under external agents.

… , the resulted improvement of elongation to break was most … be correlated with the flexibility of the poly(butyl acrylate) (PBA) component in the PSBA. An increase in elongation to break …

Abstract Flexible polyaniline having excellent mechanical properties (e.g., elongation at break = 41% and tensile strength = 1.8 kg cm −2 ) was prepared by electrochemical reduction of ordinary polyaniline in organic solvents. The flexibility is directly related with the polymer morphology which was definitely affected by the nature of electrolyte anion. Perchlorate or tetrafluoroborate anion were found suitable to obtain flexible polyaniline. At the same time, it is essential that the polymer so prepared should be reduced (undoped) in some suitable organic solvents before making a flexible free standing film.

… The mechanical strength, flexibility, energy absorption state and … Tensile strength was 12–12.5 MPa, and elongation at break … of mechanical strength, flexibility and energy absorption …

… the flexible nanocomposites was achieved up to 1.6 × 10 2 Ω cm, depending on the filler content. The elongation at the break … of the investigated nanocomposites in correlation with the …

… The correlation between electrical conductivity and elongation at break has been … described correlation of the two parameters observed for thermoplastic matrices [14], [15], [16], [17]. …

… , the elongation-at-break shows a significant negative correlation with density in a power-law fashion. For some materials, the elongation-at-break versus density correlation … be flexible …

… Electrical conductivity and elongation at break of polyurethane (PU) … in elongation at break occurs at the same filler concentration range for all investigated systems. A good correlation …

Flexible polymeric bioelectronics have the potential to address the limitations of metallic electrode arrays by minimizing the mechanical mismatch at the device-tissue interface for neuroprosthetic applications. This work demonstrates the straightforward fabrication of fully organic electrode arrays based on conductive elastomers (CEs) as a soft, flexible and stretchable electroactive composite material. CEs were designed as hybrids of polyurethane elastomers (PU) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), with the aim of combining the electrical properties of PEDOT:PSS with the mechanical compliance of elastomers. CE composites were fabricated by solvent casting of PEDOT:PSS dispersed in dissolved PU at different conductive polymer (CP) loadings, from 5 wt% to 25 wt%. The formation of PEDOT:PSS networks within the PU matrix and the resultant composite material properties were examined as a function of CP loading. Increased PEDOT:PSS loading was found to result in a more connected network within the PU matrix, resulting in increased conductivity and charge storage capacity. Increased CP loading was also determined to increase the Young's modulus and reduce the strain at failure. Biological assessment of CE composites showed them to mediate ReNcell VM human neural precursor cell adhesion. The increased stiffness of CE films was also found to promote neurite outgrowth. CE sheets were directly laser micromachined into a functional array and shown to deliver biphasic waveforms with comparable voltage transients to Pt arrays in in vitro testing.

… a major enhancement in flexibility as identified by the improvement in elongation at break. FR-… nanocomposite thin films and improves their thermal stability but decreases their flexibility. …

Stretchable self‐powered sensors are of significant interest in next‐generation wearable electronics. However, current strategies for creating stretchable piezoelectric sensors based on piezoelectric polymers or 0–3 piezoelectric composites face several challenges such as low piezoelectric activity, low sensitivity, and poor durability. In this paper, a biomimetic soft‐rigid hybrid strategy is used to construct a new form of highly flexible, high‐performance, and stretchable piezoelectric sensor. Inspired by the hinged bivalve Cristaria plicata, hierarchical droplet‐shaped ceramics are manufactured and used as rigid components, where computational models indicate that the unique arched curved surface and rounded corners of this bionic structure can alleviate stress concentrations. To ensure electrical connectivity of the piezoelectric phase during stretching, a patterned liquid metal acts as a soft circuit and a silicone polymer with optimized wettability and stretchability serves as a soft component that forms a strong mechanical interlock with the hierarchical ceramics. The novel sensor design exhibits excellent sensitivity and durability, where the open circuit voltage remains stable after 5000 stretching cycles at 60% strain and 5000 twisting cycles at 180°. To demonstrate its potential in heathcare applications, this new stretchable sensor is successfully used for wireless gesture recognition and assessing the progression of knee osteoarthritis.

Purpose Understanding how material jetting process parameters affect material properties can inform design and print orientation when manufacturing end-use components. This study aims to explore the robustness of material properties in material jetted components to variations in processing environment and build orientation. Design/methodology/approach The authors characterized the properties of six different material gradients produced from preset “digital material” mixes of polypropylene-like (VeroWhitePlus) and elastomer-like (TangoBlackPlus) materials. Tensile stress, modulus of elasticity and elongation at break were analyzed for each material printed at three different build orientations. In a separate ten-week study, the authors investigated the effects of aging in different lighting conditions on material properties. Findings Specimens fabricated with their longest dimension along the direction of the print head travel (X-axis) tended to have the largest tensile strength, but trends in elastic modulus and elongation at break varied between the rigid and flexible photopolymers. The aging study showed that the ultimate tensile stress of VeroWhitePlus parts increased and the elongation decreased over time. Material properties were not significantly altered by lighting conditions. Research limitations/implications Many tensile specimens failed at the neck region, especially for the more elastomeric parts. It is hypothesized that this is due to the material jetting process approximating curves with a pixelated droplet arrangement, instead of curved contour as seen in other additive manufacturing processes. A new tensile specimen design that performs more consistently with elastomer-like materials should be considered. The aging component of this study is focused solely on polypropylene-like (VeroWhitePlus) material; additional research into the effects of aging on multiple composite materials is needed. Originality/value The study provides the first known description of orientation effects on the mechanical behavior of photopolymers containing varied concentrations of elastomeric (TangoBlackPlus) material. The aging study presents the first findings on how time affects parts made via material jetting.

This study examined the tensile and fixed elongation properties of flexible composite made of styrene–acrylic, vinyl acetate-ethylene copolymer emulsion (VAE emulsion), and cement as cementitious material for airport pavement joint sealant. Quantitative analysis of the elastic recovery ratio and a series of specimen tensile indicators after water immersion, drying–wetting cycles, and corrosive solution (H2SO4, NaOH, and jet fuel) immersion were performed. Results showed excellent polymer-based cement flexible composite (PCFC) resistance against water and corrosive solution erosion, such as failure mode, elastic recovery, tensile strength, and energy absorption. When the level of water/corrosive solution erosion (immersion time, cycles) were increased, the tensile and fixed elongation properties progressively decreased. Specimens retained more than 60% elastic recovery ratio after water/corrosive solution erosion immersion for 30 days. According to erosion testing as per immersion time in corrosive solution, jet fuel had the maximum effect, NaOH solution had the least effect, and H2SO4 solution had an intermediary effect. At immersion time in the range of 1–30 days, the tensile strength does not change by more than 0.07 MPa. Within the limits of the fixed elongation tests, cohesive failure occurred after jet fuel immersion for 30 days, adhesive failure occurred after H2SO4 solution immersion for 30 days but was normal in other cases.

… materials, which has attracted significant research interest, especially for the engineering materials with mechanical flexibility … As a result, the tensile strength and elongation at failure of …

Traditional ceramic materials are suboptimal for use in complex environments because of their brittleness and sensitivity to flaws. As such, developing flexible and elastic ceramic materials is extremely urgent in frontier domains where high‐frequency vibration or high‐intensity bending environments are inevitable. Fibrillation of ceramic materials is an effective way for the transition of brittleness to flexibility and elasticity, due to its ability to absorb and dissipate stresses through large axial deformations. Here, a comprehensive review of the newly emerging flexible and elastic ceramic fiber materials is presented, starting from an introduction to the fundamental concept, followed by an in‐depth analysis of the relationship between their microstructures and mechanical behaviors, laying emphasis on the toughening mechanism of both individual fibers and fiber assemblies. Finally, current challenges and future development are demonstrated. It is expected that this review may provide meaningful guidance for the advancement of ceramic fiber materials toward better performance and brighter prospects.

… of flexible wearable devices, energy supply devices serving flexible wearable devices have also become a research hotspot. Hydrogels are gaining ground in the field of flexible energy …

Thermoplastic polyurethane (TPU) is used to produce elastomeric parts with superior wear/abrasion resistance, toughness, shock absorption properties, and flexibility, even at low temperatures. The production of this material through additive manufacturing (AM) techniques has been increasing because of the possibility of tuning the mechanical properties using structural design and build process parameters. Despite the data being limited, TPU produced by AM, mainly based on material extrusion, is much stiffer than the corresponding produced by conventional manufacturing, and, therefore, it shows a limited elongation. This study presents the mechanical characterization of TPU produced by the infrared light powder bed fusion (PBF-IrL) system (HP multi-jet fusion), which has recently been introduced. The properties are compared with TPU produced by open (3ntrA4) and closed (Markforged) material extrusion (MEX) systems. For the open FDM, the effects of the processing conditions are investigated to improve the material elongation and UTS with respect to the data reported in the literature for AM and conventional manufacturing. For this reason, an extensive and comprehensive review has been carried out. Compared to material extrusion, PBF-IrL TPU specimens showed higher Young’s modulus, but poorer A%. Considering the samples produced by MEX and compared to previous results in the literature, the properties obtained in this study are superior both in terms of UTS and A%.

… The polyamide segments synthesized from dimer acid and 2-methyl-1,5-diaminopentane exhibited characteristics of softness and high elongation. Using isophorone diamine as a …

In recent years, flexible sensors have rapidly become an emerging research topic. Nevertheless, most existing flexible sensors focus primarily on strain and pressure or force. Curvature, as a crucial measurement parameter, especially for evaluating the posture of soft & rigid robots or humans, however, has been rarely studied relatively. Here, we propose an ultra-flexible liquid metal curvature sensor based on a double-layer multi-microchannel structural design. The sensor can measure the bending by electric resistance variations, instead of relying on elongations like most flexible curvature sensors used now. When the sensor is bent, the embedded microchannel filled with liquid metal becomes narrow under compressive stress, and then due to the linear increase in electric resistance of the liquid metal, the curvature can be effectively measured. Subsequently, we introduce an easy and low-cost manufacturing method for curvature sensor. Then a theoretical model is established to further verify the rationality and functionality of the sensor. Finally, we present experimental results to estimate the sensor characterization. It proves that the ultra-flexible liquid metal curvature sensor has a higher sensitivity within a wide range degree, very low hysteresis and is still robust in withstanding >800 repeated loading and unloading cycles.

… were typically non-flexible and brittle, our polyimine-amides are flexible with elongation at break 380 % for PIAX1 and 65 % for PIAX2, where the higher flexibility of PIAX1 is deduced to …

… The elongation at break and notched impact strength of the PLA–… and biodegradable PLA with high rigidity and flexibility. … is a critical prerequisite for preparing “rigid and flexible” PLA. …

… −3 and 19.2% elongation at break. The discontinuous SiO 2 … is a prerequisite for practical applications of flexible films. In … tensile strength and elongation at break among the SP series. …

… properties, which is a prerequisite for the creation of high-… -12PANI demonstrated an elongation at break of 700% and … , and the elongation at break and strength at break could reach 800…

… of flexible strain sensor with MXene as conductive substance. The tensile strength and elongation at break of … In addition, the NIPU elastomer-based flexible strain sensor exhibited fast …

… flexibility and gas barrier property, as well as high elongation, … polymers, which is a prerequisite for PLA-based polymers with … This enhanced elongation at break and the tensile strength …

… , with high elongation at break and very flexible 24. This … where the polymer chain breaks down by nonenzymatic reaction (… Although it is a prerequisite, biodegradability of PBAT alone …

Self-powered wearable electronics require thermoelectric materials simultaneously with a high dimensionless figure of merit (zT) and good flexibility to convert the heat discharged by the human body into electricity. Ag2(S,Se)-based semiconducting materials can well satisfy these requirements, and thus, they are attracting great attention in thermoelectric society recently. Ag2(S,Se) crystalizes in an orthorhombic structure or monoclinic structure, depending on the detailed S/Se atomic ratio, but the relationship between its crystalline structure and mechanical/thermoelectric performance is still unclear to date. In this study, a series of Ag2Se1‐xSx (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.45) samples were prepared and their mechanical and thermoelectric performance dependence on the crystalline structure was systematically investigated. x = 0.3 in the Ag2Se1‐xSx system was found to be the transition boundary between orthorhombic and monoclinic structures. Mechanical property measurement shows that the orthorhombic Ag2Se1‐xSx samples are brittle while the monoclinic Ag2Se1‐xSx samples are ductile and flexible. In addition, the orthorhombic Ag2Se1‐xSx samples show better electrical transport performance and higher zT than the monoclinic samples under a comparable carrier concentration, most likely due to their weaker electron-phonon interactions. This study sheds light on the further development of flexible inorganic TE materials.

… to mechanical load. Balancing material strength versus ductility, as well as considering the relationship … A more flexible, ductile adhesive can undergo plastic deformation and extend to …

… relationships and the approaches employed to manage film morphology to optimize both mechanical … film stiffness and improve ductility, so that the mechanical behavior may not be as …

Abstract Multi‐component copolymerized donors (MCDs) have gained significant interest and have been rapidly developed in flexible organic solar cells (f‐OSCs) in recent years. However, ensuring the power conversion efficiency (PCE) of f‐OSCs while retaining ideal mechanical properties remains an enormous challenge. The fracture strain ( FS ) value of typical high‐efficiency blend films is generally less than 8 %, which is far from the application standards of wearable photovoltaic devices. Therefore, we developed a series of novel MCDs after meticulous molecular design. Among them, the consistent MCD backbone and end‐capped functional group formed a highly conjugated molecular plane, and the solubilization and mechanical properties were effectively optimized by modifying the proportion of solubilized alkyl chains. Consequently, due to the formation of entangled structures with a frozen blend film morphology considerably improved the high ductility of the active layer, P1 0.8 /P2 0.2 ‐TCl exhibited efficient PCE in rigid (18.53 %) and flexible (17.03 %) OSCs, along with excellent FS values (16.59 %) in pristine films, meanwhile, the outstanding FS values of 25.18 % and 12.3 % were achieved by P1 0.6 /P2 0.4 ‐TCl ‐based pristine and blend films, respectively, which were one of the highest records achieved by end‐capped MCD‐based binary OSCs, demonstrating promising application to synchronize the realization of high‐efficiency and mechanically ductile flexible OSCs.

… flexible and physically robust organic solar cells requires detailed knowledge of the mechanical … likely have a unique relationship between mechanical behavior and device performance…

Polymer-supported metal films as interconnects for flexible, … of interfacial properties on the ductility of polymer-supported … interfacial fracture energy on the ductility of polymer-supported …

Supermacroporous hydrogels have attracted wide concern due to their comfort and breathability in wearable health-monitoring applications. Size controllable supermacroporous structure and excellent mechanical properties are the most important for its application. However, they are normally fabricated by the cryogelation method, which is difficult to control pore size and maintain flexibility. Here, yeast fermentation-inspired gelatin hydrogels with a controllable supermacroporous structure and excellent mechanical properties were fabricated for the first time. The pore size can be controlled by adjusting the content of glucose and yeast, the ratio of glucose to yeast, fermentation time, and gelatin content during fermentation. The hydrogels demonstrated a controllable pore size range from 100 to 400 μm and rapid swelling characteristics. The mechanical properties were maintained by soaking ammonium sulfate solution for 12 h, showing maximum tensile and compressive strains over 300 and 99%, respectively. This novel approach can be easily applied to the preparation of supermacroporous and high ductility hydrogels under mild conditions. Furthermore, conductive hydrogels combined supermacroporous structures with conductive polyaniline and reduced oxidized graphene, and silver nanowires were prepared as wearable flexible sensors. The obtained sensors maintain well-distributed porosity, breathability, and mechanical flexibility, also showing excellent conductivity of 2.4 S m-1. Finally, the sensors were successfully applied to detect physiological signals and human-computer interaction.

… Developing high-strength, highly-ductility, thermally conductive composites to address … to the inherent difficulty in balancing strength and ductility. Here, we introduce a strategy that …

… [11] produced CNF-GNP nanopapers for flexible electronics thermal management using a … than a ductile flexible nanopaper. Xiong et al. [20] investigated the mechanical and thermal …

High power conversion efficiency (PCE) and mechanical robustness are key requirements for wearable applications of organic solar cells (OSCs). However, almost all highly efficient photoactive films comprising polymer donors (PD) and small molecule acceptors (SMAs) are mechanically brittle. In this study, highly efficient (PCE = 17.91%) and mechanically robust (crack‐onset strain [COS] = 11.7%) flexible OSCs are fabricated by incorporating a ductile oligomeric acceptor (DOA) into the PD:SMA system, representing the most flexible OSCs to date. The photophysical, mechanical, and photovoltaic properties of D18:N3 with different DOAs are characterized. By introducing DOA DOY‐C4 with a longer flexible alkyl linker and lower polymerization, the D18:N3:DOY‐C4‐based flexible OSCs exhibit a significantly higher PCE (17.91%) and 50% higher COS (11.7%) than the D18:N3‐based device (PCE = 17.06%, COS = 7.8%). The flexible OSCs based on D18:N3:DOY‐C4 retain 98% of the initial PCE after 2000 consecutive bending cycles, showing greater mechanical stability than the reference device (maintaining 89% of initial PCE). After careful investigation, it is hypothesized that the enhancement in mechanical properties is mainly due to the formation of tie chains or entanglement in the ternary blend films. These results demonstrate that DOAs have great potential for achieving high‐performance flexible OSCs.

All-polymer solar cells have shown great potential as flexible and portable power generators. These devices should offer good mechanical endurance with high power-conversion efficiency for viability in commercial applications. In this work, we develop highly efficient and mechanically robust all-polymer solar cells that are based on the PBDTTTPD polymer donor and the P(NDI2HD-T) polymer acceptor. These systems exhibit high power-conversion efficiency of 6.64%. Also, the proposed all-polymer solar cells have even better performance than the control polymer-fullerene devices with phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor (6.12%). More importantly, our all-polymer solar cells exhibit dramatically enhanced strength and flexibility compared with polymer/PCBM devices, with 60- and 470-fold improvements in elongation at break and toughness, respectively. The superior mechanical properties of all-polymer solar cells afford greater tolerance to severe deformations than conventional polymer-fullerene solar cells, making them much better candidates for applications in flexible and portable devices. All-polymer solar cells have advantages over fullerene-based solar cells due to improved stability and tunable chemical and electronic properties. Here, Kim et al.develop highly efficient and robust solar cells based on PBDTTTPD and P(NDI2HD-T), highlighting their potential in flexible and portable electronics.

… copolymers of rigid and flexible blocks in improving mechanical properties in comparison … 340 MPa for the oriented polymer composite. The ultimate elongation of the oriented blend is …

This paper describes effects of the flexibility, length, and branching of side chains on the mechanical properties of low-bandgap semiconducting polymers. The backbones of the polymer chains comprise a diketopyrrolopyrrole (DPP) motif flanked by two furan rings and copolymerized by Stille polycondensation with thiophene (DPP2FT). The side chains of the DPP fall into three categories: linear alkyl (C8, C14, or C16), branched alkyl (ethylhexyl, EH, or hexyldecyl, HD), and linear oligo(ethylene oxide) (EO3, EO4, or EO5). Polymers bearing C8 and C14 side chains are obtained in low yields and thus not pursued. Thermal, mechanical, and electronic properties are plotted against the number of carbon and oxygen atoms in the side chain. We obtain consistent trends in the thermal and mechanical properties for branched alkyl and linear oligo(ethylene oxide) side chains. For example, the glass transition temperature (Tg) and elastic modulus decrease with increasing number of carbon and oxygen atoms, whereas the crack-onset strain increases. Among polymers with side chains of 16 carbon and oxygen atoms (C16, HD, and EO5), C16 exhibits the highest Tg and the greatest susceptibility to fracture. Hole mobility, as measured in thin-film transistors, appears to be a poor predictor of electronic performance for polymers blended with [60]PCBM in bulk heterojunction (BHJ) solar cells. For example, while EO3 and EO4 exhibit the lowest mobilities (< 10–2 cm2 V–1 s–1) in thin-film transistors, solar cells made using these materials performed the best (efficiency > 2.6%) in unoptimized devices. Conversely, C16 exhibits the highest mobility (≈ 0.2 cm2 V–1 s–1) but produces poor solar cells (efficiency < 0.01%). We attribute the lack of correlation between mobility and power conversion efficiency to unfavorable morphology in the BHJ solar cells. Given the desirable properties measured for EO3 and EO4, the use of flexible oligo(ethylene oxide) side chains is a successful strategy to impart mechanical deformability to organic solar cells, without sacrificing electronic performance.

… The solubility and flexibility of polymers allows for devices to … reel-to-reel; however, this flexibility does not indicate elasticity. … severe property degradation even with minimal elongation. …

Metal-organic framework (MOF) materials have an enormous potential in separation applications, but to realize their potential as semipermeable membranes they need to be assembled into thin continuous macroscopic films for fabrication into devices. By using a facile immersion technique, we prepared ultrathin, continuous zeolitic imidazolate framework (ZIF-8) membranes on titania-functionalized porous polymeric supports. The coherent ZIF-8 layer was surprisingly flexible and adhered well to the support, and the composite membrane could sustain bending and elongation. The membranes exhibited molecular sieving behavior, close to the theoretical permeability of ZIF-8, with hydrogen permeance up to 201×10(-7)  mol m(-2)  s(-1)  Pa(-1) and an ideal H2 /CO2 selectivity of 7:1. This approach offers significant opportunities to exploit the unique properties of MOFs in the fabrication of separation and sensing devices.

In the operation of chips and other electronic components, the inability to effectively dissipate heat to ensure high-efficiency operation has always been a problem that hinders their development. To address this issue, this paper prepares a Thermal Interface Phase Change Material (TIPCM) by melt blending paraffin wax (PW) with styrene-ethylene-butylene-styrene (SEBS) and adding dicumyl peroxide as a crosslinking agent to form and reinforce a PW-SEBS crosslinked network. TIPCM maintains its structural integrity even above the melting temperature of PW due to the chemically crosslinked SEBS network, solving the leakage problem of phase change materials. Moreover, the material possesses self-healing capabilities, with the degree of self-healing reaching up to 70 % of its original state. Boron nitride (BN) is added as a thermally conductive filler, which increases the thermal conductivity of the TIPCM by 348.14 %, meeting the high thermal conductivity requirements of thermal interface materials. After the addition of the ceramic material BN, the TIPCM still possesses flexible characteristics and its tensile break elongation rate is as high as 129.1 %. Its adaptive capability allows it to better conform to the surfaces of various components to reduce contact thermal resistance. The TIPCM exhibits excellent thermal management performance for chips, reducing the temperature of the simulated CPU to 51 °C and 66 °C at 4 V and 5 V, respectively, when used in conjunction with a radiator. This significantly reduces the adverse effects of contact thermal resistance and provides a new option for chip thermal management applications.

… been associated with flexible, printed electronics is organic … touted advantages of organic electronic materials, especially if … and stretching, it is the absolute extensibility prior to fracture, …

… The dream of low-cost flexible electronic has continued to … curved, and constantly moving, flexible and stretchable devices are … modulus of 6 MPa and an elongation at break of 140%. In …

… flexible organic light emitting displays (OLED) is the fracture of extremely thin brittle conducting transparent oxide films deposited on thin flexible … essential for designer of flexible OLED. …

Many flexible electronic surfaces comprise inorganic films on organic substrates. Mechanical failure of such integrated structures of stiff and compliant materials poses a significant challenge. This letter studies the stretchability of metal films on elastomer substrates. Our experiment shows that, when stretched, elastomer-supported metal films rupture at strains larger than those reported for freestanding films. We use a finite element code to simulate the rupture process of metal films. A freestanding metal film ruptures by forming a single neck. By contrast, a metal film on an elastomer substrate may develop an array of necks before rupture. While the pre-rupture necks do not change the electrical conductance appreciably, they elongate the metal film, leading to a large overall rupture strain.

… Therefore, flexible electronics still faces challenges for … , bending, twisting, and stretching) larger than fracture limit of those … As examples of stretchability, the epidermal electronic system-…

… The two strain limits he and hc in Fig. 1 represent a significant aspect of the … deformation feature for soft materials. The he and hc differ from each other for the uniaxial deformation mode, …

… arterial material under the plane stress state varying from the uniaxial to equal biaxial tension… We calculate the local failure criteria including the maximum principal stress, the maximum …

… both material systems in the brittle limit, these results suggest that irreversible deformation—… well understood, 1 soft materials like hydrogels and elastomers fail through distinct stress …

Highly-deformable materials, from synthetic hydrogels to biological tissues, are becoming increasingly important from both fundamental and practical perspectives. Their mechanical behaviors, in particular the dynamics of crack propagation during failure, are not yet fully understood. Here we propose a theoretical framework for the dynamic fracture of highly-deformable materials, in which the effects of a dynamic crack are treated with respect to the nonlinearly deformed (pre-stressed/strained), non-cracked, state of the material. Within this framework, we derive analytical and semi-analytical solutions for the near-tip deformation fields and energy release rates of dynamic cracks propagating in incompressible neo-Hookean solids under biaxial and uniaxial loading. We show that moderately large pre-stressing has a marked effect on the stress fields surrounding a crack's tip. We verify these predictions by performing extensive experiments on the fracture of soft brittle elastomers over a range of loading levels and propagation velocities, showing that the newly developed framework offers significantly better approximations to the measurements than standard approaches at moderately large levels of external loadings and high propagation velocities. This framework should be relevant to the failure analysis of soft and tough, yet brittle, materials.

… Hence, failure of the viscoelastic material is achieved by limiting the equilibrium (long term) energy growth \(W^{\infty }\). The stress tensor S is determined from Eqs. 10 and 8 yielding: …

… Understanding the failure of soft materials requires knowledge of … Third, deformations in soft materials are related to the … We will omit all numerical prefactors in this introduction and limit …

… Although the failure strengths of soft materials are typically … This theoretical limit indicates that it is possible to design … Under deformation, the shorter chains can pull hidden segments …

… soft heterogeneous systems is that the liquid droplets deform … that had previously been adopted for soft materials.8, 41 In … to determine the onset of failure (maximum force). The fracture …

Simple computer models have been used to investigate a variety of pattern formation processes associated with material failure and deformation. These models reproduce surprisingly …

The tensile behavior of a flexible epoxy resin reinforced with knitted reinforcements from various fiber materials was comprehensively studied in the wale and course direction. By measuring dry yarns, temperature‐treated yarns, dry knitted fabrics and flexible composites, the effect of the fiber material and the knitted fabric on the tensile properties was analyzed. The interlock knit structure strongly affected the deformation behavior of the flexible composites which differed significantly from the dry knitted fabrics. The deformation behavior of the flexible composites was monitored using digital image correlation which revealed the formation of cracks and high local strain differences in the course direction for all fiber materials. This was linked to fiber‐matrix debonding by scanning electron microscope observations. In the wale direction, the deformation of the knitted structure under tensile load led to plastic deformation of the matrix material. Overall, with yarns from recycled thermoplastic fibers, a higher maximum stress and strain at break was achieved compared to bio‐based fibers. However, irreversible damage occurred for all fiber materials at similar strain values. Tensile tests on yarns, knitted fabrics and flexible composites. Investigation of the effect of fiber material on mechanical properties. High local strain differences in composites due to knitted structure. Fiber‐matrix debonding in course direction. Plastic deformation of the matrix material in the wale direction.

… tensile mechanical response of a soft polymer material (Clear Flex 75) is investigated using a split Hopkinson tension bar (SHTB). Stress-strain … The final fracture surface is examined by …

The use of flexible electronics has increased in recent years. In order to have robust and long lasting flexible displays and sensors, the combined electro-mechanical behavior needs to be assessed. The most common method to determine electrical and mechanical behavior of conductive thin films used in flexible electronics is the fragmentation test, or uniaxial tensile straining of the film and substrate. When performed in situ fracture and deformation behavior can be determined. The use of in situ electrical resistance measurements can be informative about the crack onset strain of brittle layers, such as transparent conductors, or the stretchability of metal interconnects. The combination of in situ electrical measurements with in situ X-ray or confocal laser scanning microscopy can provide even more information about the failure mechanisms of the material systems. Lattice strains and stresses can be measured with X-rays, while cracking and buckle delaminations can be studied with confocal laser scanning microscopy. These new combinations of in situ methods will be discussed as well as methods to quantify interfacial properties of conductive thin films on polymer substrates. The combined techniques provide valuable correlated electrical and mechanical data needed to understand failure mechanisms in flexible devices.

Abstract Fused Filament Fabrication (FFF) is one of the most popular 3D printing processes that can be used to manufacture flexible parts. With the use of kirigami structures, the load-carrying capability and elongation of these parts can be significantly improved. In this work, we investigate the impact of stacking sequence, slit size, and thickness on the tensile properties of 3D printed flexible kirigami specimens. In addition, we demonstrate how the transition phenomenon and out-of-plane deformation can significantly improve percent elongation at their breaking point. Considering the deformed shape during testing, specimens with a combination of layers printed along and transverse to their length showed the highest tensile break strength and the percent break elongation (2.43 MPa and 183 %, respectively). It is also determined that the occurrence of the transition phenomenon depends on the specimen’s thickness, and was observed for the 1 mm and 1.5 mm thick samples.

… (2) using tensile stress versus strain measurements (Figure 1 g). The rupture strain for DCY and … [ 11,12 ] Nanomaterials with excellent nanoscale flexibility and electrical properties have …

Flexible optoelectronics, as promising components hold shape-adaptive features and dynamic strain response under strain engineering for various intelligent applications. 2D materials with atomically thin layers are ideal for flexible optoelectronics because of their high flexibility and strain sensitivity. However, how the strain affects the performance of 2D materials-based flexible optoelectronics is confused due to their hypersensitive features to external strain changes. It is necessary to establish an evaluation system to comprehend the influence of the external strain on the intrinsic properties of 2D materials and the photoresponse performance of their flexible optoelectronics. Here, a focused review of strain engineering in 2D materials-based flexible optoelectronics is provided. The first attention is on the mechanical properties and the strain-engineered electronic properties of 2D semiconductors. An evaluation system with relatively comprehensive parameters in functionality and service capability is summarized to develop 2D materials-based flexible optoelectronics in practical application. Based on the parameters, some strategies to improve the functionality and service capability are proposed. Finally, combining with strain engineering in future intelligence devices, the challenges and future perspective developing 2D materials-based flexible optoelectronics are expounded.

… that the tensile stress–strain … failure/activation stress for a particular fracture mode is reached, the mechanism is triggered. The failure strain, which defines the point when the material …

Defects in chemical vapor deposition (CVD) graphene seriously weaken its mechanical properties, and are harmful to other impressive physical properties. In particular, the poor mechanical properties of CVD graphene with defects are one of the most significant obstacles for graphene-based flexible electronics. In this mini-review, the types of defects in CVD graphene generated during the growth and handling stages are first briefly discussed. Then, the fracture behaviors of graphene with such defects are described. In addition, several effective methods for the direct or indirect early detection of those defects present in graphene are summarized. Lastly, recent studies to overcome these mechanical limitations induced by defects are introduced.

… materials are matrix materials allowing large strain deformation and reinforcement structures allowing bending. Apart from the tensile strength … The tensile strength usually follows the …

Abstract Phase change materials are most potential candidates for storing solar thermal energy with large enthalpy and high exergy. However, the intrinsic drawback such as poor optical absorptive capacity, low thermal conductivity and poor tensile strength restrict the thermal efficiency of phase change materials. To overcome drawback, expanded graphite is used to encapsulate the paraffin then thermoplastic elastomer is used to mix with the powders with twin-screw extrusion technology. The highly flexible phase change composite shows a melting enthalpy of 124.6 J g−1 and a thermal conductivity of 2.2 W m−1 K−1 with 70% of expanded graphite/paraffin. The tensile strength of 2.1 MPa and a breaking elongation of 220%. This flexible phase change composite demonstrates good photo-thermal energy charging/discharging property and shows much larger exergy than traditional fluids in the solar thermal energy systems.