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A supercapacitor is a potential electrochemical energy storage device with high‐power density (PD) for driving flexible, smart, electronic devices. In particular, flexible supercapacitors (FSCs) have reliable mechanical and electrochemical properties and have become an important part of wearable, smart, electronic devices. It is noteworthy that the flexible electrode, electrolyte, separator and current collector all play key roles in overall FSCs. In this review, the unique mechanical properties, structural designs and fabrication methods of each flexible component are systematically classified, summarized and discussed based on the recent progress of FSCs. Further, the practical applications of FSCs are delineated, and the opportunities and challenges of FSCs in wearable technologies are proposed. The development of high‐performance FSCs will greatly promote electricity storage toward more practical and widely varying fields. However, with the development of portable equipment, simple FSCs cannot satisfy the needs of integrated and intelligent flexible wearable devices for long durations. It is anticipated that the combining an FSC and a flexible power source such as flexible solar cells is an effective strategy to solve this problem. This review also includes some discussions of flexible self‐powered devices. In this review, the unique mechanical properties, structural designs, and fabrication methods of each flexible component are systematically classified, summarized, and discussed based on the recent progress of flexible supercapacitors (FSCs). Further, the practical applications of FSCs are delineated, and the opportunities and challenges of FSCs in wearable technologies are proposed.

Implantable medical devices (IMDs) have become indispensable medical tools for improving the quality of life and prolonging the patient's lifespan. The minimization and extension of lifetime are main challenges for the development of IMDs. Current innovative research on this topic is focused on internal charging using the energy generated by the physiological environment or natural body activity. To harvest biomechanical energy efficiently, piezoelectric and triboelectric energy harvesters with sophisticated structural and material design have been developed. Energy from body movement, muscle contraction/relaxation, cardiac/lung motions, and blood circulation is captured and used for powering medical devices. Other recent progress in this field includes using PENGs and TENGs for our cognition of the biological processes by biological pressure/strain sensing, or direct intervention of them for some special self‐powered treatments. Future opportunities lie in the fabrication of intelligent, flexible, stretchable, and/or fully biodegradable self‐powered medical systems for monitoring biological signals and treatment of various diseases in vitro and in vivo. A brief overview of recent progress made in the area of biomechanical energy harvesters, nanosensors and stimulators in the biomedical field is provided. The applications of piezoelectric and triboelectric based devices, such as self‐powered energy sources, nerves/muscles stimulators, and nanoscale sensors for monitoring biomedical pressure and strain changes, are discussed.

Rapid advances in wearable electronics and mechno‐sensational human–machine interfaces impose great challenges in developing flexible and deformable tactile sensors with high efficiency, ultra‐sensitivity, environment‐tolerance, and self‐sustainability. Herein, a tactile hydrogel sensor (THS) based on micro‐pyramid‐patterned double‐network (DN) ionic organohydrogels to detect subtle pressure changes by measuring the variations of triboelectric output signal without an external power supply is reported. By the first time of pyramidal‐patterned hydrogel fabrication method and laminated polydimethylsiloxane (PDMS) encapsulation process, the self‐powered THS shows the advantages of remarkable flexibility, good transparency (≈85%), and excellent sensing performance, including extraordinary sensitivity (45.97 mV Pa−1), fast response (≈20 ms), very low limit of detection (50 Pa) as well as good stability (36 000 cycles). Moreover, with the LiBr immersion treatment method, the THS possesses excellent long‐term hyper anti‐freezing and anti‐dehydrating properties, broad environmental tolerance (−20 to 60 °C), and instantaneous peak power density of 20 µW cm−2, providing reliable contact outputs with different materials and detecting very slight human motions. By integrating the signal acquisition/process circuit, the THS with excellent self‐power sensing ability is utilized as a switching button to control electric appliances and robotic hands by simulating human finger gestures, offering its great potentials for wearable and multi‐functional electronic applications. Triboelectric hydrogel tactile sensor is constructed based on micro‐pyramid‐patterned DN ionic organohydrogels with two working principles. This self‐powered tactile sensor with wide environmental tolerance and excellent sensing performance is obtained with a subtle immersion treatment and a micro‐pyramid‐patterned method. Combining with a signal acquisition/process circuit, wearable electronics and human–machine interface applications are demonstrated.

Antimony selenide (Sb2Se3) is a promising candidate for photodetector applications boasting unique material benefits and remarkable optoelectronic properties. Achieving high‐performance self‐powered Sb2Se3 photodetector through a synergistic regulation of absorber layer and heterojunction interface demonstrates great potential and needs essential investigation. In this study, an effective two‐step thermodynamic/kinetic deposition technique containing sputtered and selenized Sb precursor is implemented to induce self‐assembled growth of Sb2Se3 light absorbing thin film with large crystal grains and desirable [hk1] orientation, presenting considerable thin‐film photodetector performance. Furthermore, aluminum (Al3+) cation dopant is introduced to modify the optoelectronic properties of CdS buffer layer, and further optimize the Sb2Se3/CdS (Al) heterojunction interface quality. Thanks to the suppressed carrier recombination and enhanced carrier transport kinetics, the champion Mo/Sb2Se3/CdS (Al)/ITO/Ag photodetector exhibits self‐powered and broadband characteristics, accompanied by simultaneously high responsivity of 0.9 A W−1 (at 11 nW cm−2), linear dynamic range of 120 dB, impressive ON/OFF switching ratio over 106 and signal‐to‐noise ratio of 109, record total noise determined realistic detectivity of 4.78 × 1012 Jones, and ultra‐fast response speed with rise/decay time of 24/75 ns, representing the top level for Sb2Se3‐based photodetectors. This intriguing work opens up an avenue for its self‐powered broadband photodetector applications. The thermodynamic/kinetic controlled self‐assembled growth of high‐quality Sb2Se3, accompanied with Al3+ cation doping in CdS induced heterojunction interface optimization can remarkably suppress carrier recombination and enhance carrier transport. Consequently, the champion Sb2Se3/CdS (Al) photodetector exhibits self‐powered broadband characteristics, accompanied by simultaneously high responsivity (0.9 A W−1), record detectivity (4.78 × 1012 Jones), and ultra‐fast response speed (rise/decay time of 24/75 ns).

Electronic skin (e‐skin), new generation of flexible wearable electronic devices, has characteristics including flexibility, thinness, biocompatibility with broad application prospects, and a crucial place in future wearable electronics. With the increasing demand for wearable sensor systems, the realization of multifunctional e‐skin with low power consumption or even autonomous energy is urgently needed. The latest progress of multifunctional self‐powered e‐skin for applications in physiological health, human–machine interaction (HMI), virtual reality (VR), and artificial intelligence (AI) is presented here. Various energy conversion effects for the driving energy problem of multifunctional e‐skin are summarized. An overview of various types of self‐powered e‐skins, including single‐effect e‐skins and multifunctional coupling‐effects e‐skin systems is provided, where the aspects of material preparation, device assembly, and output signal analysis of the self‐powered multifunctional e‐skin are described. In the end, the existing problems and prospects in this field are also discussed. In this review, we compile the latest work of self‐powered multifunction e‐skin, discussing related energy sources and coupling techniques. In addition, the latest progress of multifunctional self‐powered e‐skin for applications in physiological health, human–machine interaction (HMI), virtual reality (VR), and artificial intelligence (AI) are also present.

Traditional gas sensors are facing the challenge of low power consumption for future application in smart phones and wireless sensor platforms. To solve this problem, self‐powered gas sensors are rapidly developed in recent years. However, all reported self‐powered gas sensors are suffering from high limit of detection (LOD) toward NO2 gas. In this work, a photovoltaic self‐powered NO2 gas sensor based on n‐MoS2/p‐GaSe heterojunction is successfully prepared by mechanical exfoliation and all‐dry transfer method. Under 405 nm visible light illumination, the fabricated photovoltaic self‐powered gas sensors show a significant response toward ppb‐level NO2 with short response and recovery time and high selectivity at room temperature (25 °C). It is worth mentioning that the LOD toward NO2 of this device is 20 ppb, which is the lowest of the reported self‐powered room‐temperature gas sensors so far. The discussed devices can be used as building blocks to fabricate more functional Internet of things devices. A photovoltaic self‐powered gas sensor based on MoS2/GaSe heterojunction is fabricated via mechanical exfoliation and all‐dry transfer method. Under visible light illumination, large numbers of free carriers (electrons and holes) are produced and separated in the heterojunction, thus the MoS2/GaSe heterojunction can achieve self‐powered gas sensing toward ppb‐level NO2 at room temperature.

Quantitative analysis of gait parameters, such as stride frequency and step speed, is essential for optimizing physical exercise for the human body. However, the current electronic sensors used in human motion monitoring remain constrained by factors such as battery life and accuracy. This study developed a self‐powered gait analysis system (SGAS) based on a triboelectric nanogenerator (TENG) fabricated electrospun composite nanofibers for motion monitoring and gait analysis for regulating exercise programs. The SGAS consists of a sensing module, a charging module, a data acquisition and processing module, and an Internet of Things (IoT) platform. Within the sensing module, two specialized sensing units, TENG‐S1 and TENG‐S2, are positioned at the forefoot and heel to generate synchronized signals in tandem with the user's footsteps. These signals are instrumental for real‐time step count and step speed monitoring. The output of the two TENG units is significantly improved by systematically investigating and optimizing the electrospun composite nanofibers' composition, strength, and wear resistance. Additionally, a charge amplifier circuit is implemented to process the raw voltage signal, consequently bolstering the reliability of the sensing signal. This refined data is then ready for further reading and calculation by the micro‐controller unit (MCU) during the signal transmission process. Finally, the well‐conditioned signals are wirelessly transmitted to the IoT platform for data analysis, storage, and visualization, enhancing human motion monitoring. Electrospun triboelectric gait sensing analysis system was fabricated by preparing PVDF/BaTiO3/CNT composite fiber membrane by electrospinningtechnique and introducing Ecoflex perforated array elastomer into TENG, which not only provided high output performance, but also ensured the robustness of output and the comfort of wearing. The quantitative gait parameters were uploaded to an IoT platform via wireless network for data visualization.

For the practical applications of wearable electronic skin (e‐skin), the multifunctional, self‐powered, biodegradable, biocompatible, and breathable materials are needed to be assessed and tailored simultaneously. Integration of these features in flexible e‐skin is highly desirable; however, it is challenging to construct an e‐skin to meet the requirements of practical applications. Herein, a bio‐inspired multifunctional e‐skin with a multilayer nanostructure based on spider web and ant tentacle is constructed, which can collect biological energy through a triboelectric nanogenerator for the simultaneous detection of pressure, humidity, and temperature. Owing to the poly(vinyl alcohol)/poly(vinylidene fluoride) nanofibers spider web structure, internal bead‐chain structure, and the collagen aggregate nanofibers based positive friction material, e‐skin exhibits the highest pressure sensitivity (0.48 V kPa−1) and high detection range (0–135 kPa). Synchronously, the nanofibers imitating the antennae of ants provide e‐skin with short response and recovery time (16 and 25 s, respectively) to a wide humidity range (25–85% RH). The e‐skin is demonstrated to exhibit temperature coefficient of resistance (TCR = 0.0075 °C−1) in a range of the surrounding temperature (27–55 °C). Moreover, the natural collagen aggregate and the all‐nanofibers structure ensure the biodegradability, biocompatibility, and breathability of the e‐skin, showing great promise for practicability. In this study, a bio‐inspired multifunctional electronic skin (e‐skin) with a multilayer nanostructure based on spider web and ant tentacle is constructed, which can collect biological energy through a triboelectric nanogenerator for the simultaneous detection of pressure, humidity, and temperature. Moreover, the natural collagen aggregate and the all‐nanofiber structure ensure the biodegradability, biocompatibility, and breathability of the e‐skin.

Wearable and implantable electroceuticals (WIEs) for therapeutic electrostimulation (ES) have become indispensable medical devices in modern healthcare. In addition to functionality, device miniaturization, conformability, biocompatibility, and/or biodegradability are the main engineering targets for the development and clinical translation of WIEs. Recent innovations are mainly focused on wearable/implantable power sources, advanced conformable electrodes, and efficient ES on targeted organs and tissues. Herein, nanogenerators as a hotspot wearable/implantable energy‐harvesting technique suitable for powering WIEs are reviewed. Then, electrodes for comfortable attachment and efficient delivery of electrical signals to targeted tissue/organ are introduced and compared. A few promising application directions of ES are discussed, including heart stimulation, nerve modulation, skin regeneration, muscle activation, and assistance to other therapeutic modalities. An overview of the most recent innovations in wearable and implantable electroceuticals (WIEs) with focus on nanogenerator (NG) power sources, advanced conformable electrodes, and efficient electrostimulation on targeted organs and tissues is presented. The NG‐based technology is foreseeable to transform the concurrent WIEs toward the next generation of precision electrotherapy in the near future.

Human–machine interfaces are essential components between various human and machine interactions such as entertainment, robotics control, smart home, virtual/augmented reality, etc. Recently, various triboelectric‐based interfaces have been developed toward flexible wearable and battery‐less applications. However, most of them exhibit complicated structures and a large number of electrodes for multidirectional control. Herein, a bio‐inspired spider‐net‐coding (BISNC) interface with great flexibility, scalability, and single‐electrode output is proposed, through connecting information‐coding electrodes into a single triboelectric electrode. Two types of coding designs are investigated, i.e., information coding by large/small electrode width (L/S coding) and information coding with/without electrode at a predefined position (0/1 coding). The BISNC interface shows high scalability with a single electrode for detection and/or control of multiple directions, by detecting different output signal patterns. In addition, it also has excellent reliability and robustness in actual usage scenarios, since recognition of signal patterns is in regardless of absolute amplitude and thereby not affected by sliding speed/force, humidity, etc. Based on the spider‐net‐coding concept, single‐electrode interfaces for multidirectional 3D control, security code systems, and flexible wearable electronics are successfully developed, indicating the great potentials of this technology in diversified applications such as human–machine interaction, virtual/augmented reality, security, robotics, Internet of Things, etc. A bio‐inspired spider‐net‐coding (BISNC) interface is developed with information‐coding on a single triboelectric electrode. Thereby multidirectional sensing/control using the single‐electrode interface is achieved. The device shows excellent reliability and robustness since signal recognition is in regardless of absolute amplitude and thus not affected by sliding speed/force and humidity. Furthermore, it is highly scalable for more directions sensing and diverse applications.