Mechanical Stretchability Research Articles

Mechanically Robust Skin-like Poly(urethane-urea) Elastomers Cross-Linked with Hydrogen-Bond Arrays and Their Application as High-Performance Ultrastretchable Conductors

Elastomers play an irreplaceable role in industry and daily life; however, they are usually soft and susceptible to damage. In this study, skin-like poly(urethane-urea) elastomers with high mechanical strength, stretchability, elasticity, and excellent damage resistance, damage tolerance, and healability are fabricated by cross-linking polycaprolactone (PCL) chains with hydrogen-bond arrays. The elastomer, which is denoted as PU-ASC, has a tensile strength of ∼72.6 MPa, recovery strain of ∼500%, and fracture energy of ∼161 kJ m–2. Moreover, the PU-ASC elastomer exhibits unique strain-adaptive stiffening, which endows the elastomer with the capacity to resist damage. The skin-like PU-ASC-IL conductors can be conveniently fabricated by loading ionic liquids (ILs) into the PU-ASC elastomers. The healable, stretchable, elastic, damage-resistant, and damage-tolerant PU-ASC-IL conductors show record-high mechanical performance, with tensile strength, toughness, and fracture energy values of ∼22.8 MPa, ∼164.2 MJ m–3, and ∼73.6 kJ m–2, respectively. The damage resistance and damage tolerance of the elastomers and conductors mainly originate from the disintegrable hydrogen-bond arrays, which are capable of dissipating energy, and the strain-induced crystallization of the PCL segments. Owing to the reversibility of the hydrogen-bond arrays, fractured PU-ASC and PU-ASC-IL can be conveniently healed under heating, restoring their original mechanical performance and conductivity.

PEDOT:PSS as Stretchable Conductors with Good Wettability on the Substrate through the Simultaneous Plasticization and Secondary Doping with a Cationic or Anionic Surfactant

Stretchable conductors are indispensable units of stretchable/wearable electronic devices and systems. However, the conventional conductors including metals, semiconductors, intrinsically conducting polymers, carbon nanotubes, and graphene have very limited mechanical stretchability. It is thus significant to develop stretchable conductors. Here, cationic and anionic surfactants are studied to plasticize poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) that is the most successful conducting polymer in terms of practical application for the first time. Apart from the increase in the mechanical stretchability of PEDOT:PSS, these ionic surfactants can also enhance the conductivity via secondary doping and improve the wettability on the substrate simultaneously. The cationic surfactants can increase the elongation at break of PEDOT:PSS to >50%, higher than that (≤41%) of the anionic surfactants. The different plasticization effects are ascribed to their different interactions with PEDOT:PSS. The amphiphilic cations of a cationic surfactant can associate with the negatively charged PSS– chains, thereby lowering the Coulomb attraction between PEDOT+ and PSS– chains. This can increase the freedom of the polymer chains and cause the disappearance of the hydrogen bonds among PSS(H) chains or segments. Instead, the amphiphilic anions of an anionic surfactant can substitute PSS– as the counter anions of PEDOT+, thereby increasing the freedom of the polymer chains and induce the conformational change of the PEDOT+ chains. In addition, both the cationic and anionic surfactants can enhance the conductivity of PEDOT:PSS films to about 400 S cm–1. This is ascribed to the secondary doping by these surfactants by inducing the phase segregation and conformational change of PEDOT. Hence, the PEDOT:PSS films blended with a cationic or anionic surfactant can have high mechanical stretchability and high conductivity. In addition, the ionic surfactants can greatly improve the wettability of the PEDOT:PSS solution on a hydrophobic substrate.

Super-stretchable polymer-AgPdCu superlattice electrodes for high-performance wearable electronics

Highly-stretchable and semi-transparent polytetrafluoroethylene (PTFE)/AgPdCu (APC)-PTFE-based superlattice electrodes were realized by alternately sputtering very thin APC-PTFE hybrid layers on a polyurethane (PU) substrate at room temperature. The electrical and mechanical properties of the superlattice electrodes were optimized by controlling the PTFE thickness and the number of layers of the stacked superlattice. The optimal PTFE/APC-PTFE/PTFE/APC-PTFE/PTFE superlattice electrode showed a sheet resistance of 8.5 Ohm/square and maintained a high conductivity, even at a strain of 100%. The outstanding mechanical stretchability of the superlattice electrode is attributed to the 3-dimensional conductive APC network structure in the PTFE polymer matrix . In addition, the external strain applied to the superlattice electrode led to a change in the optical transmittance that could be used for optical switching in stretchable electronics. The superlattice electrodes can be utilized to fabricate stretchable electroluminescent devices, stretchable thin film heaters, and wearable temperature sensors . This successful demonstration of stretchable devices that include highly stretchable superlattice electrodes demonstrated the feasibility of this manufacturing strategy for use in next-generation stretchable and wearable electronics . • Fabrication of highly conductive and stretchable metal-polymer 3D nanocomposites by continuous co-sputtering of polymer and metal target. • The number of stacked layers and thickness of the polymer and polymer-metal hybrid films were controlled to form an alternating superlattice structure. • The optimized electrode showed a sheet resistance of 8.5 Ohm/square, an average transmittance of 34.0% for visible light, and stretchability that reversibly maintained a high conductivity at up to 100% strain. • The optimized electrode was applied as stretchable thin-film heater, electroluminescent device, and wearable temperature sensor.

Dual-Sensing, Stretchable, Fatigue-Resistant, Adhesive, and Conductive Hydrogels Used as Flexible Sensors for Human Motion Monitoring.

Hydrogel-based sensors serve as an ideal platform for developing personalized wearable electronics due to their high flexibility and conformability. However, the weak stretchability and inferior conductivity of hydrogels have severely restricted their large-scale application. Herein, a natural polymer-based conductive hydrogel integrated with favorable mechanical properties, good adhesive performance, and excellent fatigue resistance was fabricated via interpenetrating tannic acid (TA) into a chitosan (CS) cross-linked network in an acidic aqueous solution. The hydrogel was composed of a regular hierarchical porous structure, which was built by the hydrogen bonding between TA and CS. In addition, the hydrogels exhibited adjustable mechanical properties (maximum yield stress of 7000 Pa) and good stretchability (strain up to 320%). Benefiting from the abundant catechol groups of TA, the proposed hydrogels could repeatedly adhere to various material surfaces and could be easily peeled off without residue. Moreover, the hydrogel exhibited stable conductivity, high stretching sensitivity (gauge factor of 2.956), rapid response time (930 ms), and excellent durability (>300 cycles), which can be assembled as a strain sensor to attach to the human body for precise monitoring of human exercise behavior, distinguishing physiological signals, and recognizing speech. Furthermore, the prepared hydrogels also exhibited stable sensing performance to temperature. As a result, the hydrogels exhibited dual sensory performance for both temperature and strain deformation. It is anticipated that the incorporation of strain sensors and thermal sensors will provide theoretical guidance for developing multifunctional conductive hydrogels and pave a way for the versatile application of hydrogel-based flexible sensors in wearable devices and soft actuators.

Polyethylene and Semiconducting Polymer Blends for the Fabrication of Organic Field-Effect Transistors: Balancing Charge Transport and Stretchability

Polyethylene is amongst the most used polymers, finding a plethora of applications in our lives owing to its high impact resistance, non-corrosive nature, light weight, cost effectiveness, and easy processing into various shapes from different sizes. Despite these outstanding features, the commodity polymer has been underexplored in the field of organic electronics. This work focuses on the development of new polymer blends based on a low molecular weight linear polyethylene (LPE) derivative with a high-performance diketopyrrolopyrrole-based semiconducting polymer. Physical blending of the polyethylene with semiconducting polymers was performed at ratios varying from 0 to 75 wt.%, and the resulting blends were carefully characterized to reveal their electronic and solid-state properties. The new polymer blends were also characterized to reveal the influence of polyethylene on the mechanical robustness and stretchability of the semiconducting polymer. Overall, the introduction of LPE was shown to have little to no effect on the solid-state properties of the materials, despite some influence on solid-state morphology through phase separation. Organic field-effect transistors prepared from the new blends showed good device characteristics, even at higher ratios of polyethylene, with an average mobility of 0.151 cm2 V−1 s−1 at a 25 wt.% blend ratio. The addition of polyethylene was shown to have a plasticizing effect on the semiconducting polymers, helping to reduce crack width upon strain and contributing to devices accommodating more strain without suffering from decreased performance. The new blends presented in this work provide a novel platform from which to access more mechanically robust organic electronics and show promising features for the utilization of polyethylene for the solution processing of advanced semiconducting materials toward novel soft electronics and sensors.

Flexible La0.67Sr0.33MnO3:ZnO Nanocomposite Thin Films Integrated on Mica

The integration of functional oxide thin films on flexible substrates is critical for their application in flexible electronics. Here, to achieve flexible perovskite manganite oxide film with excellent low-field magnetoresistance (LFMR) effect, textured La0.67Sr0.33MnO3 (LSMO):ZnO nanocomposite film was deposited on a flexible mica substrate with ZnO buffer using pulsed laser deposition (PLD). Compared to the polycrystalline LSMO:ZnO nanocomposite film directly deposited on mica without buffer, the LSMO:ZnO/ZnO/mica sample exhibits larger saturation magnetization (164 emu/cm3) and higher Curie temperature (∼319 K), which results from the crystallinity and strain in the LSMO phase. In addition, the LSMO:ZnO/ZnO/mica film presents a high MR value of ∼39% at 10 K under 1 T. Furthermore, the good mechanical stretchability and property stability of the nanocomposite thin films have been demonstrated with mechanical bending.

Reprint of: Triboelectric nanogenerator-based wearable electronic devices and systems: Toward informatization and intelligence

Nowadays, wearable electronic devices with rich functions have significantly facilitated individual combat in the military and daily lives of people. To achieve implanting and sustainable wearable electronic systems, it is necessary to develop self-powered sensors utilizing environmental energy harvesting with superior mechanical stretchability and flexibility. Triboelectric nanogenerators (TENGs) can capture the low-frequency mechanical energy in human motion and convert it into electricity, which is expected to be a potential solution for this urgent need. In this review, based on advanced applications, the rich functions of TENG-based wearable devices are thoroughly discussed, including human body perception and human-machine interaction, personnel identification, as well as generation and recognition of coded information. Then, we elaborate on three crucial strategies for achieving an optimal design of TENG-based wearable devices, including selection and optimization of flexible materials, structural design and optimization, and synergistic information acquisition using multiple sensors. The representative signal processing methods are investigated to exploit the potential information behind the output signals, including basic qualitative waveform features and quantization thresholds, anti-interference processing and joint processing of multiple signals, and implementation of complex functions based on artificial intelligence. The review concludes with an overview of the remaining key challenges and potential technologies that can achieve the ultimate goal of a “fully self-powered wearable microsystem”.

Notch Flexure as Kirigami Cut for Tunable Mechanical Stretchability towards Metamaterial Application

ABSTRACT Kirigami is an art of paper cutting, which can be used in mechanical metamaterials, actuators, and energy absorption based on its deployable and load-deflection characteristics. Traditional cuts with zero width produce undesirable plastic deformation or even tear fracture due to stress concentration in stretching. This study proposes to enlarge the cut width into a notch flexure, which is applied to an orthogonality-cutted kirigami sheet, which buckles out of plane into a 3D configuration patterns under uniaxial tension. The use of compliant beam as the notch makes the stress distribution around the cuts more uniform in both elastic and elastoplastic regime. The experimental and numerical results show that by tuning the geometric parameters of cuts and material properties of the sheets, the trigger condition of 3D patterns can be adjusted. Potential capability of tunable phononic wave propagation in this kirigami-inspired metamaterial is demonstrated. This design methodology offers a theoretical guide for kirigami-based structures.

Influence of moderate electric field on sodium caseinate structure and its techno-functionality

This study aimed to evaluate the effect of moderate electric field (MEF) treatment, as a non-thermal technology, on the structure and techno-functionality of sodium caseinate. Colloidal dispersions of caseinate were subjected to different MEF processing conditions (2.56 V cm −1 for 1 and 2 h, 38.46 V cm −1 for 5 and 20 s) and their structural, physical, emulsifying and film-forming characteristics were assessed. The Fourier transform infrared (FTIR) analysis of the caseinate showed higher β-structures and a reduction in random coil conformation after MEF. The MEF-treated dispersions exhibited smaller particle size and developed emulsions with higher physical stability. The process increased the tensile strength (by 6.52–27.37%) and stretchability (by 12.17–54.30%) of caseinate film. A higher glass transition temperature in MEF-processed caseinate films was confirmed by modulated differential scanning calorimetry (MDSC) profiles. The scanning electron microscope (SEM) images showed a more uniform microstructure in treated caseinate films. The results suggest that MEF may be efficiently applied for mild modification of the structure of caseinate resulting in its property improvement. • Moderate electric field (MEF) treatment was applied to sodium caseinate. • MEF presented significant actions on the caseinate structure. • Non-thermal effects of MEF enhanced caseinate techno-functionality. • Treated caseinate yielded emulsions with higher stability and smaller droplet size. • MEF-subjected caseinate films possessed higher mechanical strength and stretchability.

Stretchable polymer composite film based on pseudo-high carbon-filler loadings for electromagnetic interference shielding

Polymer composites with carbon-based filler (C-filler) are regarded as promising alternatives for flexible and stretchable electromagnetic interference (EMI) shielding materials. However, the poor mechanical properties caused by high-loadings largely hinders their practical applications, especially for the film. Herein, a class of pseudo-high C-filler (PHCF) composite films are constructed by introducing lean C-filler polymer phase on both sides of the high C-filler polymer phase. Not only does conductive structure of the high C-filler phase not transform, but the lean C-filler phase serves as both absorbing microwaves and supporting function. Strong interfacial compatibility and multi-level “zigzag” cracks synergistically enhance the mechanical stretchability with elongation at break of 200 ± 8%. Notably, its EMI shielding effectiveness reaches 31.8 dB with enhanced absorptivity (>0.2). Further, EMI shielding performance remains reliable after bending and stretching. This work offers a regulation strategy to upgrade EMI shielding materials for burgeoning stretchable, wearable and mini electronics.

Fabrication and characterization of pectin films incorporated with clove essential oil emulsions stabilized by modified sodium caseinate

The objective of this work was to develop pectin films with antioxidant activity through the incorporation of clove essential oil (CEO) emulsions stabilized by cold plasma- (CP) and moderate electric field- (MEF) treated sodium caseinate. The CEO emulsions fabricated by CP- and MEF-treated caseinate revealed smaller droplet size and higher physical stability than the untreated caseinate. The pectin films embedded by CEO emulsions were evaluated in terms of structure, morphology, and thermal stability, as well as DPPH scavenging activity, mechanical, physical, and UV-Vis light barrier properties. The FTIR, MDSC and SEM results demonstrated the compatibility between pectin and impregnated CEO emulsions. The stabilization of CEO with CP- and MEF-treated caseinates provided substantially higher mechanical strength and stretchability, and more CEO retention during the storage time in the pectin films compared to untreated caseinate. These outcomes highlight the great potential of pectin films incorporated by CP- and MEF-treated caseinate CEO emulsions to be applied as active green packaging for extending the shelf-life of foodstuffs susceptible to oxidation, and as a promising alternative to minimize the adverse environmental effects.

Fabrication of graphene reinforced silicone‐based 3D printed tactile sensor: An approach towards an applicable piezo‐sensor

AbstractHighly sensitive, wearable, and durable tactile sensors are vital for developing smart robots, human–machine interfaces, and health monitoring systems. Although current techniques for developing tactile sensors achieve high performance, they suffer from fabrication complexity, complex working principle, short lifetime, low stretchability, and, in some cases, low sensitivity. Herein, we present a facile, cost‐effective, and scalable method for creating a 3D printed composite film of a tactile sensor made of natural rubber (NR) coated photosensitive elastomer resin (PR)/graphene nanoplatelet composite film. The addition of graphene nanoplatelet (GnP) not only improves the mechanical properties, stretchability, and flexibility of the PR/GnP composite film but also becomes responsible to produce the piezoresponse even under slight mechanical deformation in the flexible film. Furthermore, the proposed NR coating nullifies the possibility of producing interfering triboelectricity during its application as a highly sensitive pressure sensor. It also provides a low‐cost protective layer for the active material as well as the flexibility of the overall device.

Stretchable and Flexible Non‐Enzymatic Glucose Sensor Based on Poly(ether sulfone)‐Derived Laser‐Induced Graphene for Wearable Skin Diagnostics

AbstractThe laser‐induced graphene (LIG) has a great potential in electrochemically active electrodes for wearable biosensors. Herein, for the first time, a stretchable and non‐enzymatic glucose sensor based on LIG derived from commercial poly(ether sulfone) (PES) membranes is reported. The LIG is in situ transferred onto an elastomer and tightly wrapped by the elastomer in one laser carbonization step. Superior to the conventional casting and demolding transfer process, this method avoids the LIG's morphology distortion and loss. By adjusting the laser settings and the patterns, hierarchically structured electrodes are prepared with greatly increased surface areas for glucose detection. The electrodeposited dendritic gold‐nanoparticles act as the catalyst for glucose sensing. The optimized flexible sensor demonstrates a linear range for glucose from 10 μm to 10.0 mm and a detection limit of 26 μm. The sensor shows a sensitivity of 0.024 ± 0.001 mA mm−1 and selectivity toward other interfering metabolites, as well as excellent performance under mechanical bending (stable performance after 500 bending cycles) and stretchability (resistance unchanged after 1000 cyclic stretching at 20% strain). Due to the simplicity of preparation and extraordinary fidelity, the novel PES‐LIG sensor is a promising candidate for the next generation of skin‐adherent diagnostic devices and wearable electronics.

Stretchable conductive yarn with extreme electrical stability pushes fabrication of versatile textile stretchable electronics

Textile stretchable electronics can conform to the curved human skin, thus make favorable elements for various wearable applications. However, mechanical stretchability of the electronic textiles has been overemphasized, instead of the essential electrical characteristics, such as conductivity and electrical stability. In this work, we report a stretchable textile interconnects, i.e., the multi-layer helical yarn (MLHY). Thanks to the helical structural configuration and incorporation of metal fibers, these conductive yarns not only show supreme stretching capability, but also remain ultrahigh conductivity with nearly 100% electrical stability before failure. It’s further demonstrated that, MLHYs can be easily integrated in textile structures, through sewing, weaving, or knitting technologies. Hence, we suggest that MLHYs are reliable and promising stretchable interconnects, which can promote the fabrication of versatile textile stretchable electronics.

Highly Conducting and Stretchable Double-Network Hydrogel for Soft Bioelectronics.

Conducting polymer hydrogels are promising materials in soft bioelectronics because of their tissue-like mechanical properties and the capability of electrical interaction with tissues. However, it is challenging to balance electrical conductivity and mechanical stretchability: pure conducting polymer hydrogels are highly conductive, but they are brittle; while incorporating the conducting network with a soft network to form a double network can improve the stretchability, its electrical conductivity significantly decreases. Here, the problem is addressed by concentrating a poorly crosslinked precursor hydrogel with a high content ratio of the conducting polymer to achieve a densified double-network hydrogel (5.5wt% conducting polymer), exhibiting both high electrical conductivity (≈10 S cm-1 ) and a large fracture strain (≈150%), in addition to high biocompatibility, tissue-like softness, low swelling ratio, and desired electrochemical properties for bioelectronics. A surface grafting method is further used to form an adhesive layer on the conducting hydrogel, enabling robust and rapid bonding on the tissues. Furthermore, the proposed hydrogel is applied to show high-quality physiological signal recording and reliable, low-voltage electrical stimulation based on an in vivo rat model. This method provides an ideal strategy for rapid and reliable tissue-device integration with high-quality electrical communications.

Water-Based Highly Stretchable PEDOT:PSS/Nonionic WPU Transparent Electrode.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has the merits of high electrical conductivity and solution processability, and can be dispersed in water. To improve the stretchability of PEDOT:PSS-based transparent electrode films, the intrinsically conducting polymer PEDOT:PSS was blended with highly stretchable nonionic waterborne polyurethane (WPU) and coated on a thermoplastic polyurethane (TPU) film. Nonionic WPU has good compatibility with PEDOT:PSS, without affecting the acidity. WPU undergoes hydrogen bonding and coulombic attractions with PEDOT:PSS. With variation of the WPU content, differences in the electrical properties, such as the sheet resistance and mechanical stretchability, of the coated thin films were observed. The film with 2.0 wt% WPU could be stretched to 400% of the electrode surface without damage to the surface of the electrode films. The WPU and TPU films both have a polyester group, which provides good adhesion between the WPU-based transparent electrodes and the TPU substrate films. A stretchable alternating current electroluminescence (ACEL) device was constructed by using the water-based PEDOT:PSS/nonionic WPU composite as both the bottom and top transparent electrodes. The fabricated ACEL remained its initial luminance in the 500% stretched state.

Highly stretchable van der Waals thin films for adaptable and breathable electronic membranes.

The conformal integration of electronic systems with irregular, soft objects is essential for many emerging technologies. We report the design of van der Waals thin films consisting of staggered two-dimensional nanosheets with bond-free van der Waals interfaces. The films feature sliding and rotation degrees of freedom among the staggered nanosheets to ensure mechanical stretchability and malleability, as well as a percolating network of nanochannels to endow permeability and breathability. With an excellent mechanical match to soft biological tissues, the freestanding films can naturally adapt to local surface topographies and seamlessly merge with living organisms with highly conformal interfaces, rendering living organisms with electronic functions, including leaf-gate and skin-gate transistors. On-skin transistors allow high-fidelity monitoring and local amplification of skin potentials and electrophysiological signals.

A Flexible, Wearable, and Wireless Biosensor Patch with Internet of Medical Things Applications.

Monitoring the vital signs and physiological responses of the human body in daily activities is particularly useful for the early diagnosis and prevention of cardiovascular diseases. Here, we proposed a wireless and flexible biosensor patch for continuous and longitudinal monitoring of different physiological signals, including body temperature, blood pressure (BP), and electrocardiography. Moreover, these modalities for tracking body movement and GPS locations for emergency rescue have been included in biosensor devices. We optimized the flexible patch design with high mechanical stretchability and compatibility that can provide reliable and long-term attachment to the curved skin surface. Regarding smart healthcare applications, this research presents an Internet of Things-connected healthcare platform consisting of a smartphone application, website service, database server, and mobile gateway. The IoT platform has the potential to reduce the demand for medical resources and enhance the quality of healthcare services. To further address the advances in non-invasive continuous BP monitoring, an optimized deep learning architecture with one-channel electrocardiogram signals is introduced. The performance of the BP estimation model was verified using an independent dataset; this experimental result satisfied the Association for the Advancement of Medical Instrumentation, and the British Hypertension Society standards for BP monitoring devices. The experimental results demonstrated the practical application of the wireless and flexible biosensor patch for continuous physiological signal monitoring with Internet of Medical Things-connected healthcare applications.

Gelatin-Reinforced Zwitterionic Organohydrogel with Tough, Self-Adhesive, Long-Term Moisturizing and Antifreezing Properties for Wearable Electronics.

Strong mechanical performance, appropriate adhesion capacity, and excellent biocompatibility of conductive hydrogel-based sensors are of great significance for their application. However, conventional conductive hydrogels usually exhibit insufficient mechanical strength and adhesion. In addition, they will lose flexibility and conductivity under subzero temperature and a dry environment owing to inevitable freezing and evaporation of water. In this study, a tough, flexible, self-adhesive, long-term moisturizing, and antifreezing organohydrogel was prepared, which was composed of gelatin, zwitterionic poly [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) (PSBMA), MXene nanosheets, and glycerol. Natural gelatin was incorporated to enhance mechanical performance via the entanglement of a physical cross-linked network and a PSBMA network, which was also used as a stabilizer to disperse MXene into the organohydrogel. Zwitterionic PSBMA endowed the organohydrogel with good adhesion and self-healing properties. Long-term moisturizing properties and antifreeze tolerance could be achieved owing to the synergistic water retention capacity of PSBMA and glycerol. The resulting PSBMA-gelatin-MXene-glycerol (PGMG) organohydrogel exhibited high mechanical fracture strength (0.65 MPa) and stretchability (over 1000%), excellent toughness (3.87 MJ/m3), strong and repeated adhesion to diverse substrates (e.g., paper, glass, silicon rubber, iron, and pig skin), good fatigue resistance (under the cyclic stretching-releasing process), and rapid recovery capacity. Moreover, the PGMG organohydrogel showed good stability under -40 °C. The sensor based on PGMG organohydrogel could tightly attach to the human skin and real-time-monitor the motions of joints (e.g., bending of the finger, wrist, elbow, and knee) and the change in mood such as smiling and frowning. Therefore, PGMG organohydrogels have a huge potential for wearable sensors under room temperature or extreme environments.

An intrinsically stretchable aqueous Zn-MnO2 battery based on microcracked electrodes for self-powering wearable electronics

Stretchable batteries are indispensable energy storage devices to power emerging wearable electronics in soft form factors. In contrast to commonly employed engineering approaches to mitigate strains through structural design, the intrinsically stretchable devices naturally exhibit skin-like mechanical deformability by using all compliant building components. Currently, the intrinsically stretchable battery often shows a significant trade-off between electrochemical performances and mechanical deformability. Here, we introduce a low-cost and scalable approach to create an intrinsically stretchable aqueous battery featuring the deployment of state-of-art battery materials and binders. The compliant current collector, in the form of a bilayer silver nanowire/carbon nanotube nanocomposites, demonstrates excellent mechanical stretchability and electrochemical stability. The microcracked electrode layer retains stable charge transport and excellent electrochemical activity under large mechanical deformations through firm attachment to the bilayer current collector. A stretchable Zn-MnO2 cell in a sandwiched configuration is assembled exhibiting high specific capacity (>200 mAh g−1 at 100 mA g−1), excellent capacity retention of ∼90% over 100 cycles, large stretchability up to 100% strain, and durability against repetitive mechanical deformations. The practical suitability is demonstrated by a stand-alone electronic system conformably mounted on the wrist, in which an LED array is powered by a pair of stretchable Zn-MnO2 batteries.