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Stretchable triboelectric nanogenerators (TENGs) represent a new class of energy‐harvesting devices for powering wearable devices. However, most of them are associated with poor stretchability, low stability, and limited substrate material choices. This work presents the design and demonstration of highly stretchable and stable TENGs based on liquid metalel ectrodes with different phases. The conductive and fluidic properties of eutectic gallium‐indium (EGaIn) in the serpentine microfluidic channel ensure the robust performance of the EGaIn‐based TENG upon stretching over several hundred percent. The bi‐phasic EGaIn (bGaIn) from oxidation lowers surface tension and increases adhesion for printing on diverse substrates with high output performance parameters. The optimization of the electrode shapes in the bGaIn‐based TENGs can reduce the device footprint and weight, while enhancing stretchability. The applications of the EGaIn‐ and bGaIn‐based TENG include smart elastic bands for human movement monitoring and smart carpets with integrated data transmission/processing modules for headcount monitoring/control. Combining the concept of origami in the paper‐based bGaIn TENG can reduce the device footprint to improve output performance per unit area. The integration of bGaIn‐TENG on a self‐healing polymer substrate with corrosion resistance against acidic and alkaline solutions further facilitates its use in various challenging and extreme environments. [ABSTRACT FROM AUTHOR]

Efficient heat transfer control is highly demanded for dynamic thermal management of equipment and buildings especially when the environmental temperature dramatically changes. Thermal switches, the current approach of heat transfer control, suffer from the issues of low switching ratios below eight and sharp state transition between "on" and "off". Herein, a continuously‐tuned thermal regulator with an ultrahigh thermal‐conductivity change ratio of 43 based on superaligned carbon nanotube aerogel is reported, which works on the regulation of both thermal interfacial resistance and conduction pathways by compressive deformation‐induced microstructure evolution. This thermal regulator can stabilize the device temperature at 25 °C when the environmental temperature varies by 7 and 11 °C under the natural convection and forced convection conditions, respectively. Toward practical application, the thermal regulator with flexibility is wrapped around a cylindrical lithium‐ion battery to control the operation temperature within the optimal range of 20–40 °C for enhanced discharging performance even at an environmental temperature of −20 °C. Besides, by combining the thermal regulator with radiative cooling film, the house model temperature can be lowered by 2.7 °C during daytime and raised by 1.1 °C during nighttime compared with the bare one. This efficient thermal regulation approach offers an effective solution for practical thermal management. [ABSTRACT FROM AUTHOR]

Fire and explosion accidents and reduced energy utilization due to poor cycling stability of lithium‐ion batteries (LIBs) caused by inevitable internal temperature rise during high‐rate operations have become a growing concern. Herein, a dual‐functional carbon nanotube/hygroscopic salt (DFCNT/HS) film with effective passive cooling performance and fire insulation for the safe usage of practical LIBs under extremely fast discharging conditions is reported. The DFCNT/HS film based on the cooling mechanism of self‐adaptive moisture absorption/desorption delivers a high cooling power of 32.9 W m−2 K−1, which can reduce the maximum temperature of a 18650–3.6 V/2.0 Ah LIB by 11.2 and 17.4 °C at discharging rates of 10 and 15 C, respectively. Covering the cooling film, the battery discharges 23.6 Ah more total capacity at 10 within 500 cycles. What is challenging, almost three‐fold extended lifetime of 425 cycles is achieved at 15 C with an extra total capacity of 467.2 Ah. Meanwhile, the developed film also shows an excellent high‐temperature resistance up to 540 °C, which can alleviate the devastating fire propagation. The fast heat dissipation and excellent fire insulation as well as the mechanical flexibility and manufacturing scalability make this new material promising for safe usage of high‐rate LIBs with zero energy consumption. [ABSTRACT FROM AUTHOR]

Wearable sensor as the initial terminal is in great requirement for people pursuing healthy life. High‐performance tactile sensors are the guarantee of accurate pressure information acquisition. Herein, a flexible iontronic tactile sensor is developed by utilizing a highly conductive poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) thin film decorated with polymethyl methacrylate microspheres as pseudocapacitive electrode and a porous polyurethane foam composited with Na+/Cl− ion‐enriched polyvinyl alcohol gel as polymer electrolyte through a facile method of solution‐casting followed by freeze‐drying. By taking advantages of both high pseudocapacitance and rationally designed microstructures, the developed tactile sensor shows an ultrahigh sensitivity (≈162.90 kPa−1), a broad detection range (≈160 kPa), a low detection limit (≈30 Pa), a fast response time (≈25 ms), and excellent repeatability and durability. Thanks to the ultrahigh sensitivity, the sensor is capable of detecting subtle pressures caused by dynamic micromotions such as touching a sandpaper surface, dropping water droplets, and adding water into a beaker. Application of a smart glove mounted with such sensor unit and array for a fast and accurate Braille recognition is also demonstrated. The proposed facile and efficient strategy of fabricating flexible ultrasensitive tactile sensors will be favorable to various wearable subtle pressure sensing applications. [ABSTRACT FROM AUTHOR]

Recently, flexible sensors have attracted great interest for their promising application in wearable electronics. However, previous mechanical sensors are typically limited to detecting one type of stimulus and monotonous in color, which are not able to meet the sensing nor fashion requirements by customers who will wear them in daily life. Herein, a flexible and stretchable sensor based on highly conductive ionic gel is developed. Different phosphor nanoparticles are uniformly embedded into gel to enable color‐customization and even self‐illumination depending on preference. The gel is also self‐healable after complete severance and degradable in hot water. The sensors can detect multiple mechanical deformation modes to allow for detections of strain, pressure, and torsion on a single device. Wearable sensing prototypes are demonstrated with attachment to different parts of human body to detect various human motions, including strain sensing for frowning and elbow/knee bending, pressure sensing for vocal cord vibrations and pulse at wrist, and torsion sensing for shoulder and forearm rotations, through an in‐house, wireless, real‐time signal transmission and process system. Considering its sensing capability toward different stimuli as well as superior physical properties, the developed color‐customizable and self‐illuminating ionic gel sensor would find its promising applications toward wearable sensing. [ABSTRACT FROM AUTHOR]

Recently, advanced flexible tactile sensors have been widely studied for human motion detection, which is an essential part of human healthcare monitoring. New types of materials with novel composition and structures play a significant role in sensing performance improvement. Herein, a stretchable and dissolvable porous silver nanowire (Ag NW)/polyvinyl alcohol (PVA) nanocomposite hydrogel is fabricated through a facile foaming and freezing‐thawing combined approach. The PVA gel is foamed with lots of tailorable micropores to achieve much enhanced stretchability and compressibility. Ag NWs are uniformly embedded inside PVA matrix to increase the permittivity upon introduction of numerous microcapacitors. Incorporated with carbon nanotube network electrodes, a capacitive tactile sensor is developed with high sensitivity (1.9 kPa−1), wide detection range (250 kPa), quick response time (25 ms), and remarkable stability over 10 000 loading/unloading cycles. Wearable sensing demonstration of detecting various human motions is performed. The hydrogel‐based sensor can be dissolved in hot water within minutes with recycling use of electrode material, which is environmentally friendly. A large‐area integrated sensor sheet can be made upon one fabrication process followed by cut into small sensor devices with desired shapes, indicating potential customized mass production. The proposed microporous nanocomposite hydrogel‐based sensor is promising in wearable sensing applications. [ABSTRACT FROM AUTHOR]

High-power micro-supercapacitors based on micrometers-thick graphitic petal electrodes have been designed and fabricated. The electrodes were prepared by using microwave plasma chemical vapor deposition and patterned by optical lithography and reactive ion etching. Charge/discharge rates up to 100 000 mV s−1 (1000 times faster than conventional supercapacitors) have been achieved in 1 M H2SO4 aqueous electrolyte. After electrochemical oxidization treatment in 1 M H2SO4 solution at room temperature, a volumetric capacitance of 270 F cm−3 (with an area-normalized capacitance of 108 mF cm−2) was observed at a scan rate of 20 mV s−1 while maintaining high charge/discharge rates. The electrochemically treated microdevices exhibit energy densities in the range of 0.8 to 10 mWh cm−3, power densities in the range of 0.6 to 235 W cm−3, a theoretical maximum power density of 292 W cm−3 at a current of 100 μA, and good cycling stability. [ABSTRACT FROM AUTHOR]

A novel integrated 3D micro‐supercapacitor is reported. A through‐via bottom electrode technique is utilized for the first time for supercapacitor fabrication, and a highly miniaturized, flexible, and all‐solid‐state micro‐supercapacitor with 3D integration capability is achieved. Module‐wise compact integration of supercapacitors and their versatile powering applications are demonstrated. This device enables high‐power energy storage in small‐scale electronics. [ABSTRACT FROM AUTHOR]

The charge storage characteristics of a composite nanoarchitecture with a highly functional 3D morphology are reported. The electrodes are formed by the electropolymerization of aniline monomers into a nanometer-thick polyaniline (PANI) film that conformally coats graphitic petals (GPs) grown by microwave plasma chemical vapor deposition (MPCVD) on conductive carbon cloth (CC). The hybrid CC/GPs/PANI electrodes yield results near the theoretical maximum capacitance for PANI of 2000 F g−1 (based on PANI mass) and a large area-normalized specific capacitance of ≈2.6 F cm−2 (equivalent to a volumetric capacitance of ≈230 F cm−3) at a low current density of 1 A g−1 (based on PANI mass). The specific capacitances remain above 1200 F g−1 (based on PANI mass) for currents up to 100 A g−1 with correspondingly high area-normalized values. The hybrid electrodes also exhibit a high rate capability with an energy density of 110 Wh kg−1 and a maximum power density of 265 kW kg−1 at a current density of 100 A g−1. Long-term cyclic stability is good (≈7% loss of initial capacitance after 2000 cycles), with coulombic efficiencies >99%. Moreover, prototype all-solid-state flexible supercapacitors fabricated from these hybrid electrodes exhibit excellent energy storage performance. [ABSTRACT FROM AUTHOR]

The rapid development of miniaturized electronic devices has led to a growing need for rechargeable micropower sources with high performance. Among different sources, electrochemical microcapacitors or microsupercapacitors provide higher power density than their counterparts and are gaining increased interest from the research and engineering communities. To date, little work has appeared on the integration of microsupercapacitors onto a chip or flexible substrates. This review provides an overview of research on microsupercapacitors, with particular emphasis on state-of-the-art graphene-based electrodes and solid-state devices on both flexible and rigid substrates. The advantages, disadvantages, and performance of graphene-based microsupercapacitors are summarized and new trends in materials, fabrication and packaging are identified. [ABSTRACT FROM AUTHOR]