Wearable Power Sources Research Articles

In-Situ Preparation of Iron(II)-phthalocyanine@multi-Walled-CNTs Nanocomposite for Quasi-Solid-State Flexible Symmetric Supercapacitors with Long Cycling Life.

The construction of supercapacitor electrode materials with exceptional performance is crucial to the commercialisation of flexible supercapacitors. Here, a novel in-situ precipitation technique was applied for constructing iron(II)-phthalocyanine (FePc) based nanocomposite as the electrode material in quasi-solid-state flexible supercapacitors. The highly redox-active FePc nanostructures were grown in the multi-walled-CNTs (MWCNTs) networks, which shows convenient electron/electrolyte ion transport pathways along with outstanding structural stability, leading to high energy storage and long cycling life. The electrode of FePc@MWCNTs delivered a higher specific capacity than that of individual MWCNTs and FePc. The quasi-solid-state symmetric flexible device that was constructed using FePc@MWCNTs electrode demonstrated impressive performance with a maximum energy density of 29.7 Wh kg-1 and a maximum power density of 4000 W kg-1. Moreover, the device demonstrated superior durability and flexibility, as evidenced by its exceptional cyclic stability (111.3 %) even after 30000 cycles at 8 A g-1. These results reveal that the FePc@MWCNTs nanocomposite prepared by this simple in-situ precipitation method is promising as electrode material for next-generation flexible wearable power sources.

High‐performance triboelectric nanogenerators boosted by synergistically aligned piezoelectric/conductive composite nanofibers

AbstractTo address the need for efficient, flexible, and wearable power sources for portable electronics, a high performance triboelectric nanogenerator (TENG) was proposed by incorporating vertically‐aligned barium titanate (BaTiO3)/antimony tin oxide (ATO) nanofibers in polydimethylsiloxane (PDMS) negative triboelectric layer, where BaTiO3 served as piezoelectric material, and ATO served as conductive filler. Silver‐coated conductive fabric was used as electrode to ensure integrability and wearability. By strategically coupling the triboelectric effect of PDMS, the piezoelectric effect of BaTiO3 nanofibers, and the charge transfer effect of ATO nanofibers, the TENG exhibited the optimum output voltage and current of approximately 119 V and 28 μA, and power density of 11.74 μW/cm2, respectively. This device demonstrates its potential applications in energy supply by effectively illuminating 174 commercial green LEDs and charging capacitors for powering electronics. Additionally, the successful integration of the TENG into a smart fencing jacket highlights its utility in practical applications.Highlights TENGs with vertically‐aligned BaTiO3/ATO composite nanofibers was constructed. The output performance of TENGs were enhanced by coupling triboelectric and piezoelectric effects. Conductive ATO nanofibers were incorporated to enhance charge transfer for performance enhancement. A smart fencing jacket with scoring system was developed using the wearable TENG.

Multiphase soft metal enabled high-performance fabric-based wearable energy harvesting

Highly efficient and flexible power sources have always been the focus and goal in the field of wearable electronics. However, the existing wearable power sources are limited by their large size, high weight, electrolyte leakage, and poor mechanical compliance, which seriously hinders their practical applications. Herein, we propose a novel strategy to achieve and demonstrate a fabric-based high-performance wearable triboelectric nanogenerator (TENG) structure. The metals of gallium (Ga), bismuth (Bi), indium (In), and tin (Sn) are mixed according to specific mass ratios, and then they are transformed in liquid phase to form room-temperature multiphase soft metals of GaBiInSn. The material exhibits both metallic and fluidic properties, and possesses a characteristic of multiphase structure. The GaBiInSn material is directly deposited between polytetrafluoroethylene (PTFE) layers and nonwoven fabrics to establish multi-level conductive and frictional interfaces, creating charge transfer and solid-liquid hybrid dielectric layers. Therefore, the thin film-type triboelectric nanogenerators with a structure of PTFE/GaBiInSn/nonwoven fabric (LM-P-TENGs) is manufactured. The LM-P-TENGs can be integrated onto fabrics without compromising their breathability, comfortableness, and flexibility. Particularly, LM-P-TENGs efficiently convert the mechanical energy of human limb movements into sustainable electrical energy output. Under the human limb mechanical triggering conditions, LM-P-TENG achieves a champion specific open-circuit voltage up to 900 V, peak short-circuit current density of 43.3 mA/m2, and high power density of 12.56 W/m2. This work demonstrates the application potential of room-temperature multiphase soft materials in flexible wearable power sources, while introducing a novel power supply mode for wearable electronics. Additionally, the LM-P-TENGs also present applications in self-powered wearables, medical biosensing systems, human-machine interaction systems, near-eye display systems, etc. for the flexible electronics.

Phosphorus-Doped g-C3N4 Induces Self-Polarization PVDF for High-Performance Triboelectric Nanogenerator As Wearable Power Sources

In recent years, the requirement for wearable electronic energy has become increasingly popular, which can be seen from the creation of numerous energy harvesters and storage devices. Among them, a new type of energy harvesting technology named triboelectric nanogenerator (TENG) has gradually matured for nearly ten years. Increasing the output performance by enhancing the surface charge of the TENG is what most researchers have focused on recently. There are several ways such as changing the surface structures, improving the dielectric constant and spontaneous polarization, which is related to this work. Some papers mention that filling nanoparticles or adding 2-dimensional material will induce PVDF self-polarization to the beta phase, making it a highly electronegative state. Moreover, adding high electronegative atoms will also change the state of the PVDF. Therefore, we synthesize the PVDF film by adding phosphorus-doped g-C3N4 (PCN) in order to enhance the output performance. By introducing the P atom into the matrix of g-C3N4 via an annealing process, the P atom in g-C3N4 not only increases the electronegativity of the film surface but also induces PVDF to a polarized crystal b phase for absorbing more positive charges. Consequently, the TENG with PVDF/PCN displays a remarkable improvement in output performance compared to the pristine PVDF-based TENG with more than a 100 V increase. Furthermore, the flexibility and durability of PVDF/PCN thin film have the potential to be widely used in self-powered wearable sources. Figure 1

Internally connected porous PVA/PAA membrane with cross-aligned nanofiber network for facile and long-lasting ion transport in zinc–air batteries

In response to the growing interest in next-generation wearable devices, the demand for high-performance, safe, and flexible power sources has increased. Flexible zinc–air batteries (ZABs) based on gel polymer electrolytes (GPEs) have emerged as promising candidates for wearable power sources owing to their high energy density, safety, and cost efficiency. However, persistent electrolyte evaporation through the air cathode poses a significant challenge, resulting in poor lifespan characteristics that impede practical applications. In this study, we developed a polymer composite-type GPE composed of cross-aligned nanofibers (NFs) of a polyacrylic acid (PAA)-based framework embedded in a polyvinyl alcohol (PVA) matrix. Upon immersion in a liquid electrolyte (6 M KOH), the superabsorbent PAA spontaneously generated an internally connected porous (IP) structure adjacent to the aligned PAA NFs. These pores served as directional water channels, facilitating rapid hydroxide ion conduction and yielding a remarkable ionic conductivity of 235.7 mS cm−1. The PVA matrix acts as both a packaging material and the main body of the GPE, providing good dimensional stability and mitigating the swelling of PAA, even under conditions of high electrolyte uptake, while also ensuring high flexibility. The IP-PVA/PAA composite GPE demonstrated a high power output, rate performance, and excellent lifespan in flexible ZABs. Furthermore, successful operation at various bending angles provides empirical evidence supporting the viable application of flexible ZABs.

Flexible, multifunctional, ultra-light and high-efficiency liquid metal/polydimethylsiloxane sponge-based triboelectric nanogenerator for wearable power source and self-powered sensor

Triboelectric nanogenerator (TENG) has emerged as a promising solution for self-powered wearable electronic devices. However, challenges such as low energy collection efficiency and limited durability persist, particularly when subjected to mechanical input from multiple directions. Herein, we introduced a straightforward method to create a flexible liquid metal (LM)-embedded polydimethylsiloxane (PDMS) sponge-based single-electrode TENG (LMPST). Unlike traditional systems, the LMPST exhibited overwhelming merits of exceptional mechanical properties, high output performance, remarkable durability, lightweight design, multi-functionality, and a simple fabrication process due to the outstanding conductivity and liquid nature of LM within the flexible porous PDMS sponge. The LMPST demonstrated superior open-circuit voltage (82 V), short-circuit current (1.66 μA), and maximum power density (2.89 W/m2) with outstanding stability (27000 cycles) under omnidirectional mechanical input, which were unattainable by conventional systems. Furthermore, the LMPST successfully realized various practical applications, including force sensing, energy harvesting, motion detection, message transmission, and human-machine interaction. This study lays a solid foundation for the development of advanced materials and devices to drive progress in wearable electronics and smart systems.

High-energy and wearable fiber-shaped asymmetric supercapacitors based on the combination of fluorinated polyimide and Co3O4 on carbon fibers

This study reports a fiber-shaped asymmetric supercapacitor (f-ASC) made from carbonized fluorinated polyimide deposited onto carbon fiber (c-fPI@CF) as a negative electrode coupled with cobalt oxide-embedded c-fPI@CF (Co3O4@c-fPI@CF) as a positive electrode. The thermal decomposition of fPI evolves gases, mostly stemming from the fluorine-containing moiety (–CF3) of fPI. This process leads to the formation of a distinct microporous structure characterized by small graphitic regions and a high specific surface area of 1071 m2 g−1. Asymmetric configuration enlarges the operating voltage of the f-ASC, contributing to the increase in energy density. The resulting f-ASC shows a capacitance of 56 F cm−3 at 0.5 A cm−3, exceeding other fiber supercapacitors and good cycle stability even under mechanical deformation, demonstrating its feasibility as a wearable power source. It also delivers a significant energy density of 10.0 mWh cm−3 and a power density of 1.16 W cm−3. According to first-principles calculations, the graphitic structure of c-fPI increases the conductivity of Co3O4@c-fPI and stabilizes the exposed metal spots of the Co3O4. Therefore, this f-ASC exhibits great potential for future wearable energy storage systems.

Biodegradable and flame-retardant cellulose-based wearable triboelectric nanogenerator for mechanical energy harvesting in firefighting clothing

Integrating flexible triboelectric nanogenerators (TENGs) into firefighting clothing offers exciting opportunities for wearable portable electronics in personal protective technology. However, it is still a grand challenge to produce eco-friendly TENGs from biodegradable and low-cost natural polymers for mechanical-energy harvesting and self-powered sensing. Herein, conductive polypyrrole (PPy) and natural chitosan (CS)/phytic acid (PA) tribonegative materials were employed onto the Lycra fabric (LC) in turn to assemble the biodegradable and flame-retardant single-electrode mode LC/PPy/CS/PA TENG (abbreviated as LPCP-TENG). The resultant LPCP-TENG exhibits truly wearable breathability (1378.6 mm/s), elasticity (breaking elongation 291 %), and shape adaptivity performance that can produce an open circuit voltage of 0.3 V with 2 N contact pressure at a working frequency of 5 Hz with a limiting oxygen index of 35.2 %. Furthermore, facile monitoring for human motion of firefighters on fireground is verified by LPCP-TENG when used as self-powered flexible tactile sensor. In addition, degradation experiments have shown that waste LPCP-TENG can be fully degraded in soil within 120 days. This work broadens the applicational range of wearable TENG to reduce the environmental effects of abandoned TENG, exhibiting prosperous applications prospects in the field of wearable power source and self-powered motion detection sensor for personal protection application on fireground.

NiCo2O4 Nanowires Immobilized on Nitrogen-Doped Ti3C2Tx for High-Performance Wearable Magnesium-Air Batteries.

Flexible magnesium (Mg)-air batteries provide an ideal platform for developing efficient energy-storage devices toward wearable electronics and bio-integrated power sources. However, high-capacity bio-adaptable Mg-air batteries still face the challenges in low discharge potential and inefficient oxygen electrodes, with poor kinetics property toward oxygen reduction reaction (ORR). Herein, spinel nickel cobalt oxides (NiCo2O4) nanowires immobilized on nitrogen-doped Ti3C2Tx (NiCo2O4/N-Ti3C2Tx) are reported via surface chemical-bonded effect as oxygen electrodes, wherein surface-doped pyridinic-N-C and Co-pyridinic-N moieties accounted for efficient ORR owing to increased interlayer spacing and changed surrounding environment around Co metals in NiCo2O4. Importantly, in polyethylene glycol (PVA)-NaCl neutral gel electrolytes, the NiCo2O4/N-Ti3C2Tx-assembled quasi-solid wearable Mg-air batteries delivered high open-circuit potential of 1.5V, good flexibility under various bent angles, high power density of 9.8mW cm-2, and stable discharge duration to 12h without obvious voltage drop at 5mA cm-2, which can power a blue flexible light-emitting diode (LED) array and red smart rollable wearable device. The present study stimulates studies to investigate Mg-air batteries involving human-body adaptable neutral electrolytes, which will facilitate the application of Mg-air batteries in portable, flexible, and wearable power sources for electronic devices.

High-Performance All-Textile Triboelectric Nanogenerator toward Intelligent Sports Sensing and Biomechanical Energy Harvesting.

Merging textiles with advanced energy harvesting technology via triboelectric effects brings novel insights into self-powered wearable textile electronics. However, fabrication of a comfortable textile-based triboelectric nanogenerator (TENG) with high outputs remains challenging. Herein, we propose a highly flexible, tailorable, single-electrode all-textile TENG (t-TENG) with both wear comfort and high outputs. A dielectric modulated porous composite coating containing poly(vinylidene fluoride)-hexafluoropropylene copolymer and barium titanate nanoparticles is constructed on conductive fabric to counterpart with highly positive glass fiber fabric through knotted yarn bonding, maintaining the superiority of textiles and strong triboelectricity. Through the synergistic optimization of charge storage via dielectric modulation and charge dissipation offset by electrical poling, remarkable outputs (261 V, 1.5 μA, and 12.7 nC) are obtained from a miniaturized, lightweight t-TENG (2 × 2 cm2, 130 mg) with an instantaneous power density of 654.48 mW·m-2, as well as excellent electrical robustness and device durability over 20,000 cycles. The t-TENG also exhibits a high sensitivity of 3.438 V·kPa-1 in the force region (1-10 N), demonstrating great potential in TENG-based intelligent sports sensing applications for monitoring and correcting the basketball shooting hand and foot arch posture. Furthermore, over 110 light-emitting diode arrays can be lightened up by gently tapping this miniaturized t-TENG. It also offers a wearable power source scheme through integrating the single-electrode device into clothing and utilizing the skin as the grounded electrode, revealing its ease of integration and biomechanical energy harvesting capability. This work provides an attractive paradigm for next-generation textile electronics with well-balanced device performance and wear comfort.

Self‐supported VO2 on polydopamine‐derived pyroprotein‐based fibers for ultrastable and flexible aqueous zinc‐ion batteries

AbstractA conventional electrode composite for rechargeable zinc‐ion batteries (ZIBs) includes a binder for strong adhesion between the electrode material and the current collector. However, the introduction of a binder leads to electrochemical inactivity and low electrical conductivity, resulting in the decay of the capacity and a low rate capability. We present a binder‐ and conducting agent‐free VO2 composite electrode using in situ polymerization of dopamine on a flexible current collector of pyroprotein‐based fibers. The as‐fabricated composite electrode was used as a substrate for the direct growth of VO2 as a self‐supported form on polydopamine‐derived pyroprotein‐based fibers (pp‐fibers@VO2(B)). It has a high conductivity and flexible nature as a current collector and moderate binding without conventional binders and conducting agents for the VO2(B) cathode. In addition, their electrochemical mechanism was elucidated. Their energy storage is induced by Zn2+/H+ coinsertion during discharging, which can be confirmed by the lattice expansion, the formation of by‐products including Znx(OTf)y(OH)2x−y·nH2O, and the reduction of V4+ to V3+. Furthermore, the assembled Zn//pp‐fibers@VO2(B) pouch cells have excellent flexibility and stable electrochemical performance under various bending states, showing application possibilities for portable and wearable power sources.

Electromechanical coupling of a 3.88 W harvester with circumferential step-size field: modeling, validation and self-powered wearable applications

The fast advances in wearable electronic devices require clean and wearable power sources. This study presents a wearable electromagnetic energy harvester (EMEH) with high output performance mounted on the knee to obtain human vibration energy. The design forms a circumferential step-change magnetic field with high electromechanical coupling for high-efficiency energy conversion. We first formulate a theoretical model and simulate the analytical voltage via MATLAB. To predict the output performance of the EMEH, we conduct simulations via ANSYS. Subsequently, experiments are conducted to explore the output performance of the harvester in terms of the voltage, the output power, and the charging rate. The prototype generates a peak power of 3.88 W with a 449 Ω resistor under the excitation of 2.0 Hz. Additionally, the prototype charges a battery to 33.9% within 300 s at a running speed of 8 km h−1. This study provides a new perspective for advancing the development of watt-level self-powered wearables.

Synthesis of MXene-based nanocomposite electrode supported by PEDOT:PSS-modified cotton fabric for high-performance wearable supercapacitor

The rapid development of wearable and portable electronic devices prompts the ever-growing demand for wearable, flexible, and light-weight power sources. In this work, a MXene/GNS/PPy@PEDOT/Cotton nanocomposite electrode with excellent electrochemical performances was fabricated using cotton fabric as a substrate. Poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) was coated on the cotton fabric to obtain a conductive substrate through a controllable dip-drying coating process, while a nanocomposite consisting of MXene, Graphene nanoscroll (GNS), and polypyrrole (PPy) was directly synthesized and deposited on the PEDOT:PSS-modified cotton fabric via a one-step in situ polymerization method. The resultant MXene/GNS/PPy@PEDOT/Cotton electrode delivers excellent electrochemical performances including an ultra-high areal capacitance of 4877.2 mF·cm−2 and stable cycling stability with 90 % capacitance retention after 3000 cycles. Moreover, the flexible symmetrical supercapacitor (FSC) assembled with the MXene/GNS/PPy@PEDOT/Cotton electrodes demonstrates a prominent areal capacitance (2685.28 mF·cm−2 at a current density of 1 mA·cm−2) and a high energy density (322.15 μWh·cm−2 at a power density of 0.46 mW·cm−2). In addition, the application of the FSC for wearable electronic devices was demonstrated.

Enhancing thermoelectric conversion efficiency of hydrogel-based supercapacitors by the three-dimensional ion channels hydration

Ionic thermoelectric (i-TE) supercapacitors are capable of converting low-grade heat directly into electricity, which has enormous potential for wearable power sources and the Internet of Things. However, the low thermoelectric conversion efficiency limits their applications. Here, we report a method for forming polar corona in a three-dimensional (3D) network based on chitosan-polyacrylamide‑silicon dioxide (PACS) hydrogel, significantly increasing the maximum thermogalvanic power density of 187.2 mW m−2 at a temperature difference (ΔT) of 5 K. The abundant functional groups on PACS confine free H2O molecules to the polymer network, forming polar corona, reducing the volume of thermally diffused ions, and enabling rapid conduction of lithium ions (Li+) in unsaturated coordination. In addition, demonstrating an impressive ionic conductivity of 50.2 mS cm−1 as well as a maximum thermal charging voltage of 200 mV (ΔT of 8 K), this work provides a new strategy for broadening applications of ionic thermally chargeable supercapacitors in harvesting low-grade heat and wearable devices.

Serpentine liquid electrode based Dual-mode skin Sensors: Monitoring biomechanical movements by resistive or triboelectric mode

Flexible and stretchable electrodes are crucial components for wearable electronic devices. Herein, a serpentine liquid electrode based dual-mode skin sensors (SLEDSS) that leverages a highly deformable and serpentine liquid electrode is developed. The functional carboxylated multi-walled carbon nanotubes / Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (MWCNT-COOH / PEDOT: PSS) network structure endows the SLEDSS with a stable linear change in resistance. Additionally, a solid–liquid double electric layer generated between the solid surface and liquid electrode facilitates a higher triboelectric output performance. As a result, the SLEDSS features dual-modal sensing capabilities, including both resistive and triboelectric modes. The flowability of the liquid electrode enables it to fully adapt to different types of deformation, thereby allowing SLEDSS to effectively collect energy in different forms of movement, such as tapping, stretching, bending, twisting, and unpredictable transformations based on practical applications. SLEDSS can maintain its performance even at up to 550.32% strain, displaying a monotonically increasing relationship between the stretchable length and open-circuit voltage. Finally, the SLEDSS is applied as a wearable power source and self-powered sensor for monitoring biomechanical movements, the excellent stretchable performance and ultra-high sensitivity to mechanical stimulation provided by the SLEDSS offer new prospects for self-powered sensors.

A polyester/spandex blend fabrics-based e-textile for strain sensor, joule heater and energy storage applications

Electronic textiles (e-textiles), as a new class of wearable electronics, have shown diverse applications in modern technologies. However, the development of multi-functional e-textiles with both high strength and elasticity to satisfy different working conditions remains challenge. Herein, the e-textiles based on polyester/spandex blend (PSB) fabrics have been fabricated and their applications in strain sensors, heaters and supercapacitors have been systematically studied. The carbon nanotubes (CNTs) are coated on PSB fabrics via polydopamine (PDA) adhesion. As a strain sensor, the air-permeable PSB-CNT e-textiles show a gauge factor of 18.9 at high strain with a fast response time of 114 ms. The PSB-CNT strain sensor can work better than the cotton-based sensor even at high temperature of 100 °C due to the high heat resistance of polyester, securing its application in severe environment. As a joule heater, the PSB-CNT e-textiles can raise up to 110 °C at 12 V. Further electrodeposition of polypyrrole (PPy) on PSB-CNT can obtain the e-textile electrodes for micro-supercapacitor (MSC). The all-solid-state MSC using PSB-CNT-PPy delivers high specific capacitance of 550 mF cm−2 at 1 mA cm−2. This work offers a simple route for e-textile fabrications and promises potential applications in wearable sensors, heaters, and power sources.

Piezoelectric driven self-powered supercapacitor for wearable device applications

The universal energy demand and pollution have prompted research scientists to explore other energy harvesting technologies that can generate energy from the natural resource environment, mainly due to the use of conventional energy sources. Energy harvester can be extracted and to convert into useful electric energy. The piezoelectric energy harvester is an excellent method of extracting mechanical energy due to its high electric and mechanical combination and piezoelectric harvester coefficient to compare electro-static, electro-magnetic, and triboelectric transitions. Therefore, the harvesting of piezoelectric energy is highly appreciated by the scientific community. Energy harvesters can be used to convert electrical energy into strong vibrations, which can be to store and used on a variety of ultra-low power electronic devices. With the advent of a various variety of wearable digital devices and fitness tracking devices, the piezoelectric generator suitable for portable and wearable electronic power source is one of the most interesting.

Stretchable Energy Harvesting Device based on Thermoelectric Composite Films

Thermoelectric energy harvesting has attracted a lot of attention for powering self-powered devices because of the potential to generate energy anywhere with a temperature difference. In particular, a stretchable thermoelectric generator (S-TEG) can be applied to the repetitively moving parts of a machine and even a human body. Herein, we suggested a S-TEG using thermoelectric composite films made by dispersing n-type Bi2Te2.7Se0.3 powders into the polyvinylidene fluoride elastomer. The prepared n-type thermoelectric composite film with 75 wt% of Bi2Te2.7Se0.3 powders showed a power factor of 1.81 mW m−1 K−2 at room temperature. Next, we fabricated S-TEG by encapsulating thermoelectric powders-based composite films, and Ag-coated textile electrodes with an Eco-flex matrix. The fabricated stretchable energy harvester generated a maximum output power of 2.35 nW at a temperature difference (ΔT) of 25 K. By repeatedly introducing ΔT=5K, our S-TEG converted the output voltage of 3.4 mV and current signals of 0.25 mA. Moreover, a finite element analysis with multiphysics COMSOL simulation software was conducted to compare the experimental and theoretical thermoelectric output performance of the fabricated S-TEG. Finally, we demonstrated energy harvesting by converting human body heat into electrical energy for potential utilization of our energy harvester. This study led to the development of a S-TEG design using thermoelectric film with a simple and low-cost fabrication procedure, providing a potential approach for use as a next-generation wearable device power source.

Energy harvesting for self-powered wearable device applications

The universal energy demand and pollution have prompted research scientists to explore other energy harvesting technologies that can generate energy from the natural resource environment, mainly due to the use of conventional energy sources. Energy harvester can be extracted and to convert into useful electric energy. The piezoelectric energy harvester is an excellent method of extracting mechanical energy due to its high electric and mechanical combination and piezoelectric harvester coefficient to compare electro-static, electro-magnetic, and triboelectric transitions. Therefore, the harvesting of piezoelectric energy is highly appreciated by the scientific community. Energy harvesters can be used to convert electrical energy into strong vibrations, which can be to store and used on a variety of ultra-low power electronic devices. With the advent of a various variety of wearable digital devices and fitness tracking devices, the piezoelectric generator suitable for portable and wearable electronic power source is one of the most interesting.

Highly Durable Bidirectional Rotary Triboelectric Nanogenerator with a Self-Lubricating Texture and Self-Adapting Contact Synergy for Wearable Applications.

Sliding-freestanding triboelectric nanogenerators (SF-TENGs) are desirable for application in wearable power sources; however, improving their durability is the primary challenge. Meanwhile, few studies focus on enhancing the service life of tribo-materials, especially from an anti-friction perspective during dry operation. Herein, for the first time, a surface-textured film with self-lubricating property is introduced into the SF-TENG as a tribo-material, which is obtained by the self-assembly of hollow SiO2 microspheres (HSMs) close to a polydimethylsiloxane (PDMS) surface under vacuum conditions. The PDMS/HSMs film with micro-bump topography simultaneously reduces the dynamic coefficient of friction from 1.403 to 0.195 and increases the electrical output of SF-TENG by an order of magnitude. Subsequently, a textured film and self-adapting contact synergized bidirectional rotary TENG (TAB-TENG) is developed, and the superiorities of the soft flat rotator with bidirectional reciprocating rotation are systematically investigated. The obtained TAB-TENG exhibits a remarkable output stability and an outstanding mechanical durability over 350 000 cycles. Furthermore, a smart foot system for stepping energy harvesting and wireless walking states monitoring is realized. This study proposes a pioneering strategy for extending the lifetime of SF-TENGs and advances it toward practical wearable applications.