Polypyrrole/reduced graphene oxide coated fabric electrodes for supercapacitor application

Flexible and wearable energy storage devices are strongly demanded to power smart textiles. Herein, reduced graphene oxide (RGO) and polypyrrole (PPy) were deposited on cotton fabric via thermal reduction of GO and chemical polymerization of pyrrole to prepare textile-based electrodes for supercapacitor application. The obtained PPy–RGO-fabric retained good flexibility of textile and was highly conductive, with the conductivity of 1.2 S cm⁻¹. The PPy–RGO-fabric supercapacitor showed a specific capacitance of 336 F g⁻¹ and an energy density of 21.1 Wh kg⁻¹ at a current density of 0.6 mA cm⁻². The RGO sheets served as conductor and framework under the PPy layer, which could facilitate electron transfer between RGO and PPy and restrict the swelling and shrinking of PPy, thus resulting in improved electrochemical properties respect to the PPy-fabric device.     

Multi-Functional and Stretchable Thermoelectric Bi2Te3 Fabric for Strain,Pressure, and Temperature-Sensing

Fiber-based electronics are essential components for human-friendly wearable devices due to their flexibility, stretchability, and wearing comfort. Many thermoelectric (TE) fabrics are investigated with diverse materials and manufacturing methods to meet these potential demands. Despite such advancements, applying inorganic TE materials to stretchable platforms remains challenging, constraining their broad adoption in wearable electronics. Herein, a multi-functional and stretchable bismuth telluride (Bi₂Te₃) TE fabric is fabricated by in situ reduction to optimize the formation of Bi₂Te₃ nanoparticles (NPs) inside and outside of cotton fabric. Due to the high durability of Bi₂Te₃ NP networks, the Bi₂Te₃ TE fabric exhibits excellent electrical reliability under 10,000 cycles of both stretching and compression. Interestingly, intrinsic negative piezoresistance of Bi₂Te₃ NPs under lateral strain is found, which is caused by the band gap change. Furthermore, the TE unit achieves a power factor of 25.77 µWm⁻¹K⁻² with electrical conductivity of 36.7 Scm⁻¹ and a Seebeck coefficient of −83.79 µVK⁻¹ at room temperature. The Bi₂Te₃ TE fabric is applied to a system that can detect both normal pressure and temperature difference. Balance weight and a finger put on top of the 3 × 3 Bi₂Te₃ fabric assembly are differentiated through the sensing system in real time.     

Ultralow Voltage High-Performance Bioartificial Muscles Based on Ionically Crosslinked Polypyrrole-Coated Functional Carboxylated Bacterial Cellulose for Soft Robots

The development of ultralow voltage high-performance bioartificial muscles with large bending strain, fast response time, and excellent actuation durability is highly desirable for promising applications such as soft robotics, active biomedical devices, flexible haptic displays, and wearable electronics. Herein, a novel high-performance low-priced bioartificial muscle based on functional carboxylated bacterial cellulose (FCBC) and polypyrrole (PPy) nanoparticles is reported, exhibiting a large bending strain of 0.93%, long actuated bending durability (96% retention for 5 h) under an ultralow harmonic input of 0.5 V, broad frequency bandwidth up to 10 Hz, fast response time (≈4 s) in DC responses, high energy density (6.81 KJ m⁻³), and high power density (5.11 KW m⁻³), all of which mainly stem from its high surface area and porosity, large specific capacitance, tuned mechanical properties, and strong ionic interactions of cations and anions in ionic liquid with FCBC and PPy nanoparticles. More importantly, bioinspired applications such as the grapple robot, bionic medical stent, bionic flower, and wings-vibrating have been realized. These successful demonstrations offer a viable means for developing high-performance bioartificial muscles for next-generation soft bioelectronics including bioinspired robotics, biomedical microdevices, and wearable electronics.     

Metal-Organic Framework Reinforced Highly Stretchable and Durable Conductive Hydrogel-Based Triboelectric Nanogenerator for Biomotion Sensing and Wearable Human-Machine Interfaces

Flexible triboelectric nanogenerators (TENGs) with multifunctional sensing capabilities offer an elegant solution to address the growing energy supply challenges for wearable smart electronics. Herein, a highly stretchable and durable electrode for wearable TENG is developed using ZIF-8 as a reinforcing nanofiller in a hydrogel with LiCl electrolyte. ZIF-8 nanocrystals improve the hydrogel's mechanical properties by forming hydrogen bonds with copolymer chains, resulting in 2.7 times greater stretchability than pure hydrogel. The hydrogel electrode is encapsulated by microstructured silicone layers that act as triboelectric materials and prevent water loss from the hydrogel. Optimized ZIF-8-based hydrogel electrodes enhance the output performance of TENG through the dynamic balance of electric double layers (EDLs) during contact electrification. Thus, the as-fabricated TENG delivers an excellent power density of 3.47 Wm^–2, which is 3.2 times higher than pure hydrogel-based TENG. The developed TENG can scavenge biomechanical energy even at subzero temperatures to power small electronics and serve as excellent self-powered pressure sensors for human-machine interfaces (HMIs). The nanocomposite hydrogel-based TENG can also function as a wearable biomotion sensor, detecting body movements with high sensitivity. This study demonstrates the significant potential of utilizing ZIF-8 reinforced hydrogel as an electrode for wearable TENGs in energy harvesting and sensor technology.     

All‐Plastic‐Materials Based Self‐Charging Power System Composed of Triboelectric Nanogenerators and Supercapacitors

Triboelectric nanogenerators (TENG) are a possible power source for wearable electronics, but the conventional electrode materials for TENG are metals such as Cu and Al that are easy to be oxidized or corroded in some harsh environments. In this paper, metal electrode material is replaced by an electrical conducting polymer, polypyrrole (PPy), for the first time. Moreover, by utilizing PPy with micro/nanostructured surface as the triboelectric layer, the charge density generated is significantly improved, more superior to that of TENG with metals as the triboelectric layer. As this polymer‐based TENG is further integrated with PPy‐based supercapacitors, an all‐plastic‐materials based self‐charging power system is built to provide sustainable power with excellent long cycling life. Since the environmental friendly materials are adopted and the facile electrochemical deposition technique is applied, the new self‐charging power system can be a practical and low cost power solution for many applications.     

MXene Functionalized,Highly Breathable and Sensitive Pressure Sensors with Multi-Layered Porous Structure

Breathable, flexible, and highly sensitive pressure sensors have drawn increasing attention due to their potential in wearable electronics for body-motion monitoring, human-machine interfaces, etc. However, current pressure sensors are usually assembled with polymer substrates or encapsulation layers, thus causing discomfort during wearing (i.e., low air/vapor permeability, mechanical mismatch) and restricting their applications. A breathable and flexible pressure sensor is reported with nonwoven fabrics as both the electrode (printed with MXene interdigitated electrode) and sensing (coated with MXene/silver nanowires) layers via a scalable screen-printing approach. Benefiting from the multi-layered porous structure, the sensor demonstrates good air permeability with high sensitivity (770.86–1434.89 kPa⁻¹), a wide sensing range (0–100 kPa), fast response/recovery time (70/81 ms), and low detection limit (≈1 Pa). Particularly, this sensor can detect full-scale human motion (i.e., small-scale pulse beating and large-scale walking/running) with high sensitivity, excellent cycling stability, and puncture resistance. Additionally, the sensing layer of the pressure sensor also displays superior sensitivity to humidity changes, which is verified by successfully monitoring human breathing and spoken words while wearing a sensor-embedded mask. Given the outstanding features, this breathable sensor shows promise in the wearable electronic field for body health monitoring, sports activity detection, and disease diagnosis.     

Fabric electrodes coated with polypyrrole nanorods for flexible supercapacitor application prepared via a reactive self-degraded template

Wearable energy storage devices that can be used in the garment industry are strongly required to power E-textiles. In this article, polypyrrole (PPy) nanorods were deposited on cotton fabrics via in situ polymerization of pyrrole in the presence of the fibrillar complex of FeCl₃ and methyl orange as a reactive self-degraded template. The obtained fabrics could be directly used as supercapacitor electrodes, with a maximum specific capacitance of 325 F g⁻¹ and an energy density of 24.7 Wh kg⁻¹ at a current density of 0.6 mA cm⁻². The capacitance remained higher than 200 F g⁻¹ after 500 cycles.     

Radiofrequency Shielding by Polypyrrole-Coated Nano and Regular Fibrous Mats

This work investigates radiofrequency shielding by polypyrrole (PPy)-coated fibrous mats consisting of nano and regular fibers. Radiofrequency shielding protects human beings as well as electronic devices from the harmful effects of radiofrequency waves. The results of this study show that, generally, lowering the fiber diameter of the coated mats increases the reflection but decreases the absorption of radiofrequency radiation in the range of 5 GHz to 8 GHz. Moreover, absorption of higher frequencies is greater than that of lower frequencies, whereas for reflection the opposite trend is observed. The sum of absorption and reflection of radiofrequencies in the range of 5 GHz to 8 GHz by PPy-coated mats is not affected by the fiber diameter of the mats. PPy-coated regular poly(acrylonitrile) (PAN) and poly(ethylene terephthalate) (PET) fiber mats with weight per unit area of 16.67 mg/cm² provide radiofrequency shielding above 85%. Nanofibrous mats with weight per unit area of nearly 60 times less showed similar radiofrequency shielding effectiveness as regular fiber mats, highlighting the importance of the high specific surface area of nanofibers.     

3D Wearable Fabric-Based Micro-Supercapacitors with Ultra-High Areal Capacitance

Miniaturized electronics require integrated unit configuration in very limited space, where energy storage per unit area is thus extremely critical. Micro-supercapacitors (MSCs), mainly established on planar substrates, are superior but still suffer from limited areal capacitance. Herein, a novel strategy is introduced to construct high cross-section MSCs using 3D fabrics as the porous skeleton. Interdigitated poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) is patterned on 3D fabrics to achieve continuous conductive networks, while MnO₂ microspheres epitaxially grown on PEDOT:PSS are fully exposed to electrolyte with the support of fabric fibers. The unique architecture can utilize more active sites of thick electrodes and the high conductivity of interpenetrating fiber networks. The resulting fabric-based MSCs demonstrate ultra-high areal capacitance of 135.4 mF cm⁻², which is 3.5 times that of devices on polyethylene terephthalate substrates and is among the highest values for planar-based MSCs using the same interdigital geometry. Moreover, the flexible fabrics endow MSCs with extremely high bending stability with 94% capacitance retention even after 3000 cycles. These figures-of-merit enable fabric-based MSCs promising to be used in the next-generation of wearable electronics.     

In situ synthesis of CuS nano platelets on nano wall networks of Ni foam and its application as an efficient counter electrode for quantum dot sensitized solar cells

Herein, we report for the first time efficient CuS/nickel foam (NF) counter electrode for quantum dots-sensitized solar cells (QDSSCs) is fabricated using chemical bath deposition technique which can serve as a highly efficient CE for QDSSCs. These are characterized using scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), current voltage and impedance spectroscopy. The CuS/NF and CuS/FTO films are investigated as a counter electrode (CE) in QDSSCs. The QDSSC based on CuS/NF CE achieves power conversion efficiency (PCE) of 4.93% accrediting to the high fill factor (FF) of 0.58, and the PCE is greater than that of CuS/FTO CE (4.27%) for TiO₂/CdS/CdSe/ZnS electrode, under the illumination of one sun (AM1.5, 100 mW cm⁻²). Electrochemical measurements testified that CuS/NF reveals high electro-catalytic activity towards polysulfide reduction, thus accelerating QDSSCs performance. Consequently, the CuS/NF is very capable as an efficient CE for QDSSCs. This procedure not only provides high electro catalytic activity but also an efficient scheme to be used in different applications such as flexible solar cells, fuel cells and supercapacitor.     

Stretchable and Shape-Adaptable Triboelectric Nanogenerator Based on Biocompatible Liquid Electrolyte for Biomechanical Energy Harvesting and Wearable Human–Machine Interaction

The significant demand of sustainable power sources has been triggered by the development of wearable electronics (e.g., electronic skin, human health monitors, and intelligent robotics). However, tensile strain limitation and low conformability of existing power sources cannot match their development. Herein, a stretchable and shape-adaptable liquid-based single-electrode triboelectric nanogenerator (LS-TENG) based on potassium iodide and glycerol (KI-Gly) liquid electrolyte as work electrode is developed for harvesting human motion energy to power wearable electronics. The LS-TENG demonstrates high output performances (open-circuit voltage of 300 V, short-circuit current density of 17.5 mA m^–2, and maximum output power of 2.0 W m^–2) and maintains the stable output performances without deterioration under 250% tension stretching and after 10 000 cycles of repeated contact-separation motion. Moreover, the LS-TENG can harvest biomechanical energy, including arm shaking, human walking, and hand tapping, to power commercial electronics without extra power sources. The LS-TENG attached on different joints of body enables to work as self-powered human motion monitor. Furthermore, a flexible touch panel based on the LS-TENG combined with a microcontroller is explored for human–machine interactions. Consequently, the stretchable and shape-adaptable LS-TENG based on KI-Gly electrolyte would act as an exciting platform for biomechanical energy harvesting and wearable human–machine interaction.     

Nanofluid Electrolyte with Fumed Al2O3 Additive Strengthening Zincophilic and Stable Surface of Zinc Anode toward Flexible Zinc–Nickel Batteries

Flexible zinc–nickel batteries (FZNBs) have been considered as a promising power supply for wearable electronics due to the intrinsic safety, high operating voltage and superior rate performance. However, the serious self-corrosion of zinc and the redistribution of dissolved [Zn(OH)₄]²⁻ on the electrode surface limit the electrochemical performance of FZNBs. Herein, the nanofluid electrolyte with fumed Al₂O₃ additive is introduced into FZNBs and a protective layer is formed due to the adsorption of Al₂O₃ on the electrodeposited zinc anode. The protective layer strengthens the zincophilicity of the anode and homogenizes the deposition of [Zn(OH)₄]²⁻, avoiding the dendrite formation and the shape change of electrode. Meanwhile, by suppressing the [Zn(OH)₄]²⁻ diffusion from the anode surface to the bulk electrolyte, the interface stabilization is effectively promoted, thereby improving zinc utilization rate and inhibiting the corrosion. Hence, the FZNBs assembled with Al₂O₃-nanofluid electrolyte and electrodeposited zinc anode demonstrates superior energy density of 210 Wh L⁻¹ with a stable cycling of 575 h. Furthermore, FZNBs modified with Al₂O₃-nanofluid electrolyte have a promising future in the field of wearable and portable electronics.     

Sustainable 3D Structural Binder for High-Performance Supercapacitor by Biosynthesis Process

Flexible supercapacitors represent an attractive technology for the next generation of wearable consumer electronics as power sources but usually suffer from relatively low energy density. It is highly desired to construct high-performance electrodes for the practical applications of supercapacitors. Here, inspired by the natural structure of the spider web, an elaborate design of binder is reported through a biosynthesis process to construct flexible electrodes with both excellent mechanical properties and electrochemical performance. Through this strategy, a spider-web-inspired 3D structural binder enables large ion-accessible surface area and high packing density of active electrode material as well as efficient ion transport pathways. As a result, a high areal capacitance of 4.62 F cm^-2 and a high areal energy density of 0.18 mW h cm^-2 is achieved in the composite electrodes and symmetric supercapacitors, respectively, demonstrating a promising potential to construct flexible energy storage devices for diverse practical applications.     

Anisotropic ZnS Nanoclusters/Ordered Macro-Microporous Carbon Superstructure for Fibrous Supercapacitor toward Commercial-Level Energy Density

Fibrous supercapacitor (FSC) is of great attention in wearable electronics, but is challenged by low energy density, owing to disordered diffusion pathway and sluggish redox kinetics. Herein, using micro-reaction strategy, an anisotropic superstructure is developed by in situ anchoring ultrafine zinc sulfine (ZnS) nanoclusters on conductively ordered macro-microporous carbon skeleton via interfacial C S Zn bonds (ZnS/SOM-C). The anisotropic superstructure affords 3D ordered macro-microporous pathways, large accessible surfaces, and highly dispersed active sites, which exhibit enhanced electrolyte mass diffusion, rapid interfacial charge transfer, and large faradaic ions storage (capacitance of 1158 F g⁻¹ in KOH aqueous solution). By microfluidic spinning, the ZnS/SOM-C is further assembled into fibrous electrode of FSC that delivers high capacitance (791 F g⁻¹), commercial-level energy density (172 mWh g⁻¹), and durable stability. As a result, the FSC can realize wearable self-powered applications (e.g., self-cleaning ventilatory mask, smartwatch, and display), exhibiting the superiority in new energy and wearable industry.     

Carbonized Cotton Fabric for High‐Performance Wearable Strain Sensors

Recent years have witnessed the booming development of flexible strain sensors. To date, it is still a great challenge to fabricate strain sensors with both large workable strain range and high sensitivity. Cotton is an abundant supplied natural material composed of cellulose fibers and has been widely used for textiles and clothing. In this work, the fabrication of highly sensitive wearable strain sensors based on commercial plain weave cotton fabric, which is the most popular fabric for clothes, is demonstrated through a low‐cost and scalable process. The strain sensors based on carbonized cotton fabric exhibit fascinating performance, including large workable strain range (>140%), superior sensitivity (gauge factor of 25 in strain of 0%–80% and that of 64 in strain of 80%–140%), inconspicuous drift, and long‐term stability, simultaneously offering advantages of low cost and simplicity in device fabrication and versatility in applications. Notably, the strain sensor can detect a subtle strain of as low as 0.02%. Based on its superior performance, its applications in monitoring both vigorous and subtle human motions are demonstrated, showing its tremendous potential for applications in wearable electronics and intelligent robots.     

High Performing Solid-State Organic Electrochemical Transistors Enabled by Glycolated Polythiophene and Ion-Gel Electrolyte with a Wide Operation Temperature Range from −50 to 110 °C

The development of organic electrochemical transistors (OECTs) capable of maintaining their high amplification, fast transient speed, and operational stability in harsh environments will advance the growth of next-generation wearable and biological electronics. In this study, a high-performance solid-state OECT (SSOECT) is successfully demonstrated, showing a recorded high transconductance of 220 ± 59 S cm⁻¹, ultrafast device speed of ≈10 kHz with excellent operational stability over 10 000 switching cycles, and thermally stable under a wide temperature range from −50 to 110 °C. The developed SSOECTs are successfully used to detect low-amplitude physiological signals, showing a high signal-to-noise-ratio of 32.5 ± 2.1 dB. For the first time, the amplifying power of these SSOECTs is also retained and reliably shown to collect high-quality electrophysiological signals even under harsh temperatures (−50 and 110 °C). The demonstration of high-performing SSOECTs and its application in harsh environment are core steps toward their implementation in next-generation wearable electronics and bioelectronics.     

Galvanically Replaced,Single‐Bodied Lithium‐Ion Battery Fabric Electrodes

Despite extensive research on flexible/wearable power sources, their structural stability and electrochemical reliability upon mechanical deformation and charge/discharge cycling have not yet been completely achieved. A new class of galvanically replaced single‐bodied lithium‐ion battery (LIB) fabric electrodes is demonstrated. As a proof of concept, metallic tin (Sn) is chosen as an electrode active material. Mechanically compliable polyethyleneterephthalate (PET) fabrics are conformally coated with thin metallic nickel (Ni) layers via electroless plating to develop flexible current collectors. Driven by the electrochemical potential difference between Ni and Sn, the thin Ni layers are galvanically replaced with Sn, resulting in the fabrication of a single‐bodied Sn@Ni fabric electrode (Sn is monolithically embedded in the Ni matrix on the PET fabric). Benefiting from the chemical/structural uniqueness and rationally designed bicontinuous ion/electron transport pathways, the single‐bodied Sn@Ni fabric electrode provides exceptional redox reaction kinetics and omnidirectional deformability (notably, origami‐folding boats), which lie far beyond those attainable with conventional LIB electrode technologies.     

A highly flexible solid-state supercapacitor based on the carbon nanotube doped graphene oxide/polypyrrole composites with superior electrochemical performances

Flexible electrodes of ternary composites, in which highly conductive carbon nanotube films (CNFs) are coated with carbon nanotube-doped graphene oxide/polypyrrole (CNT-GO/PPy), have been fabricated via facile electrochemical synthesis. Long and short CNTs are separately doped into the composites (lCNT-GO/PPy and sCNT-GO/PPy) and their electrochemical performances are compared. Electrochemical measurements indicate that the doping of CNTs in the composites significantly improves the electrochemical behaviors of the GO/PPy electrodes. Notably, the lCNT-GO/PPy electrodes show superior electrochemical properties with respect to the sCNT-GO/PPy electrodes, which is related to the introduction of abundant CNTs in the former electrodes and their special microstructures. Two symmetric electrodes with the lCNT-GO/PPy composites coated on CNFs are assembled to fabricate a solid-state supercapacitor device, which features lightweight, ultrathinness, and high flexibility. The device achieves a high areal and volumetric specific capacitance of 70.0 mF cm⁻² at 10 mV s⁻¹ and 6.3 F cm⁻³ at 0.043 A cm⁻³, respectively. It also shows superior rate performance and cycle stability, with a capacitance retention rate of 87.7% for 10,000 cycles. The supercapacitor device fabricated is promising for the use in lightweight and flexible integrated electronics.     

A Self-Powered,Rechargeable, and Wearable Hydrogel Patch for Wireless Gas Detection with Extraordinary Performance

Flexible gas sensors play an indispensable role in diverse applications spanning from environmental monitoring to portable medical electronics. Full wearable gas monitoring system requires the collaborative support of high-performance sensors and miniaturized circuit module, whereas the realization of low power consumption and sustainable measurement is challenging. Here, a self-powered and reusable all-in-one NO₂ sensor is proposed by structurally and functionally coupling the sensor to the battery, with ultrahigh sensitivity (1.92%/ppb), linearity (R² = 0.999), ultralow theoretical detection limit (0.1 ppb), and humidity immunity. This can be attributed to the regulation of the gas reaction route at the molecular level. The addition of amphiphilic zinc trifluoromethanesulfonate (Zn(OTf)₂) enables the H₂O-poor inner Helmholtz layer to be constructed at the electrode–gel interface, thereby facilitating the direct charge transfer process of NO₂ here. The device is then combined with a well-designed miniaturized low-power circuit module with signal conditioning, processing and wireless transmission functions, which can be used as wearable electronics to realize early and remote warning of gas leakage. This study demonstrates a promising way to design a self-powered, sustainable, and flexible gas sensor with high performance and its corresponding wireless sensing system, providing new insight into the all-in-one system of gas detection.     

Polypyrrole nanotube arrays on carbonized cotton textile for aqueous sodium battery

Polypyrrole (PPy) nanotubes on carbonized cotton textile have been prepared using ammonium vanadate nanowires as sacrificial templates, and characterized by scanning electron microscope, X-ray diffraction, fourier transform infrared spectrum and transmission electron microscope. The process contains cotton textile carbonation in Ar gas, growing ammonium vanadate nanowires on the carbon textile, electrodeposition PPy layer on the nanowire, and dissolving the ammonium vanadate nanowire core to obtain PPy nanotube. The results show that pyrrole is uniformly polymerized around the ammonium vanadate nanowires and the PPy nanotubes are firmly adhere to the carbon textile. The electrochemical properties of the PPy nanotubes for aqueous sodium-ion battery are investigated with cyclic voltammetry, galvanostatic charge-discharge test, and rate performance. The results exhibit a good electrochemical performance, which delivers a high discharge capacity of 108.8 mAh g⁻¹ over 100 cycles.