Stretchable Triboelectric Nanogenerator Research Articles

Highly conductive rubber-based electrode with a robust wrinkled mesh-like copper coating for stretchable triboelectric nanogenerator

Stretchable triboelectric nanogenerators (TENGs) have gained increasing attention for their potential applications in wearable electronics. However, the fabrication of metal-coated flexible electrodes with a robust metal-polymer interface, high conductivity, and stretchability remains challenging for stretchable TENGs. Herein, a stretchable triboelectric nanogenerator (TENG) was designed using a highly conductive natural rubber (NR) electrode with a wrinkled mesh-like copper coating, which was chemically plated onto its surface by polymer-assisted metal deposition (PAMD) technology. To enable the PAMD process, a layer of polyacrylic acid (PAA) polymer brushes was first grafted onto the NR surface. This could not only assist the chemical plating but also improve the interfacial adhesion between the copper coating and the NR substrates. More importantly, the PAA layer facilitated the interconversion between the wrinkled structure and mesh-like structure of the copper coating during stretching cycles to ensure its conductivity and mechano-electrical stability. With this intrinsically stretchable rubber-based electrode, TENG devices were designed in a contact-separation configuration, which could effectively harvest mechanical energy in both pressing and stretching modes and show excellent electrical output performance. Notably, the rubber-based TENG could work stably at 100 % strain and produce a maximum power density of 0.14 mW/m2 at the resistance load of 3×107 Ω. Therefore, the stretchable rubber-based TENG in this work demonstrated a potential solution to flexible micromechanical energy harvesters for wearable devices.

A molybdenum-disulfide nanocomposite film-based stretchable triboelectric nanogenerator for wearable biomechanical energy harvesting and self-powered human motion monitoring

Triboelectric nanogenerators (TENGs) are receiving significant interest in the wearable electronics industry owing to their distinct ability to capture ambient energy, particularly from human endeavors. Because they can serve as renewable sources of energy and multifunctional sensing devices. Herein, a stretchable TENG (S-TENG) based on micropatterned fabric-coated molybdenum disulfide (MoS2) and an Ecoflex nanocomposite as the electron-acceptor layer is newly developed for harvesting biomechanical energy to power wearable electronics and enable self-powered sensing. Incorporating the MoS2 monolayer in the composite creates microchannels on the surfaces, improving the conductivity of the composite by facilitating ion transport. Moreover, the incorporation of the monolayer provides an additional triboelectric output by increasing the contact area, enhancing the dielectric constant, and modulating the surface charge density. The use of knitted fabric materials enhances the extensibility (230 %) of the composite film. A thorough investigation was conducted to assess the electric output performance, resulting in the attainment of a maximum peak power density of 11 W/m2. This power density is sufficient to provide electricity to a typical electronic equipment with low power consumption. Regarding passive sensing, the suggested S-TENG may be used as a pressure sensor, with a high sensitivity of 17.18 V/kPa. Furthermore, active sensing enables the identification of dynamic movements in the joints of the human body by establishing a relation between gestures and the corresponding electrical signals. This study presents an innovative approach for developing a wearable S-TENG that exhibits dual-mode energy-harvesting and sensing capabilities, including the use in biomedical applications and human-machine systems.

Ultra-stretchable and anti-freezing ionic conductive hydrogels as high performance strain sensors and flexible triboelectric nanogenerator in extreme environments

Conductive hydrogels have shown promising applications in a variety of portable smart wearable electronics and flexible sensors due to their high flexibility, stretchability, adjustable mechanical properties and excellent electrical conductivity. However, most of the current hydrogel-based flexible strain sensors and portable triboelectric nanogenerator (TENG) generally suffer from low stretchability/flexibility, poor mechanical properties, weak low-temperature tolerance and low power output. Herein, a multifunctional ionic conductive hydrogel (PPAVC-BA) with ultra-stretchability (∼1750%), high transparency (85%), high electrical conductivity (13.7 mS/cm), and outstanding anti-freezing properties (below −80°C without freezing). The strain sensor assembled from the PPAVC-BA hydrogel shows high sensitivity (GF=4.43) and ultra-wide sensing detection range (0%-1100%) as well as fast response time. Based on these properties, the PPAVC-BA hydrogel strain sensor can accurately recognize different joint movements of the human body as well as weak muscle beats. In addition, the PPAVC-BA hydrogel-based TENG (PPAVC-BA-TENG) exhibits excellent electrical output performance, with an open circuit voltage (Voc) of about 420 V, a short circuit current (Isc) of 23 μA, a short-circuit transfer charge (Qsc) of 112 nC and a maximum power density of 2246.03 mW/m2, which allows it to power small electronic devices. This PPAVC-BA-TENG also shows outstanding tensile performance and can output stable electrical signals at 200% strain. Impressively, the PPAVC-BA-TENG exhibits good electrical output performance even at low temperature of −50°C and high temperature of 80°C. The flexible strain sensors and stretchable TENG for high performance and multifunctionality reported in this work provide viable references in the development of motion detection, energy harvesting and self-powered electronic devices.

Highly stretchable kirigami-patterned nanofiber-based nanogenerators for harvesting human motion energy to power wearable electronics

Wearable electronics are advancing towards miniaturization and flexibility. However, traditional energy supply methods have largely hindered their development. An effective solution to this problem is to convert human mechanical energy into electricity to power wearable electronic devices. Therefore, it is greatly attractive to design flexible, foldable and even stretchable energy harvesting devices. Herein, we use the electrospinning and kirigami approach to develop a type of highly stretchable kirigami-patterned nanofiber-based triboelectric nanogenerator (K-TENG). Due to its innovative structural design, the K-TENG can achieve a tensile strain of 220%, independent of the tensile properties of the material itself. When a person swings their arms, the K-TENG fixed to the clothing can convert mechanical energy from human movement into electrical energy. The produced electricity can directly drive 50 LED lights and a digital watch, or be stored in a lithium battery to charge the smartwatch and smartphone, respectively. This study employs a new method to fabricate a stretchable triboelectric nanogenerator and demonstrates its promising applications in wearable power technology.

Flexible Triboelectric Nanogenerators based on Hydrogel/g-C3N4 Composites for Biomechanical Energy Harvesting and Self-Powered Sensing.

Flexible and stretchable triboelectric nanogenerators (TENGs) have been rapidly advanced owing to the demand for portable and wearable electronic devices that can work under universal or motional circumstances. While versatile materials can be applied in a TENG as dielectric materials, flexible and cost-effective electrodes are crucially important for the output performance of TENGs. Herein, we developed a poly(vinyl alcohol) (PVA) hydrogel TENG doped with a novel two-dimensional material, graphitic carbon nitride (g-C3N4), which could act as both a cost-effective flexible electrode and a positive dielectric for TENG with different morphologies. The measured peak-to-peak open-circuit voltage of the TENG reached 80 V at a dopant concentration of 2.7 wt % in single-electrode mode, which is far higher than that of the pristine PVA hydrogel TENG. As a demonstration of the application, the g-C3N4/PVA hydrogel TENG can be adopted as electronic skin to monitor the movement of the human body. Low-frequency mechanical energy-harvesting devices in different morphologies including discoid flake shape, tube shape, and spiral shape in the single-electrode mode or contact-separation mode have been designed, fabricated, and evaluated. All of these merits of the proposed hydrogel TENG after doping two-dimensional (2D) material g-C3N4 have demonstrated their promising potential for versatile applications in biomechanical energy harvesting and self-powered sensing.

Largely Improving the Output Performance of Stretchable Triboelectric Nanogenerators via Thermo-Compressive Technology.

Stretchable triboelectric nanogenerators (TENGs) are widely applied in wearable and implantable electronics, smart medical devices, and soft robots. However, it is still a challenge to produce stretchable TENGs with both exceptional elasticity and output performance, which limits their application scope. In this work, high-performance stretchable TENGs are developed through a thermo-compression(TC) fabrication process. In particular, a poly(vinylidene fluoride) film is compactly bound to the elastic thermoplastic polyurethane substrate, which inherits excellent stretchability with a strain of up to 815%. Furthermore, owing to the large surface area, tight contact, and effective vertical transport of tribo-induced charges between the coupled fibrous tribo-layer and soft substrate, the TC composite film-based TENGs exhibit a greater output (2-4 times) than unlaminated film-based TENGs. Additionally, the broad universality of this method is proven using various tribo- and substrate materials. The proposed technology provides a novel and effective approach to conjointly boost the output and stretchability of TENGs, showing encouraging application prospects in self-powered wearable and flexible electronics.

Highly Stretchable MXene‐based Meta‐Aerogels with Near‐Zero and Negative Poisson's Ratios

AbstractMXene‐based aerogels are promising candidates for wearable electronics due to their unique structures and properties. However, the reported MXene‐based aerogels show poor stretchability, significantly restricting their applications in wearable electronics. Herein, unprecedented highly stretchable MXene‐based aerogels with crimpled and reentrant microstructures are developed via synergistic assembly of MXene and flexible polymers combined with uniaxial and biaxial hot‐pressing strategies. The uniaxially hot‐pressed MXene‐based meta‐aerogels show compressed and crimpled microstructures and combine ultrahigh stretchability up to 427%, high elasticity, high compressibility, high fatigue resistance upon compression and stretching, and near‐zero Poisson's ratios. The biaxially hot‐pressed MXene‐based meta‐aerogels exhibit reentrant microstructures and achieve high stretchability and negative Poisson's ratios upon stretching in different directions, which have never been realized by traditional aerogels. It is demonstrated that they can be used for ultrabroad‐range pressure/strain sensors, highly stretchable triboelectric nanogenerators, and smart thermal management with tunable thermal insulation and Joule heating performances achieved by stretching. This work opens a new way to highly stretchable aerogels with near‐zero and negative Poisson's ratios promising in wearable electronics, nanogenerators, thermal management, energy storage, etc.

Self-strengthening and conductive cellulose composite hydrogel for high sensitivity strain sensor and flexible triboelectric nanogenerator

Triboelectric nanogenerators (TENGs) as promising energy harvesting devices have gained increasing attention. However, the fabrication of TENG simultaneously meets the requirements of green start feedstock, flexible, stretchable, and environmentally friendly remains challenging. Herein, the hydroxyethyl cellulose macromonomer (HECM) simultaneously bearing acrylate and hydroxyl groups was first synthesized and used as a crosslinker to prepare the chemically and physically dual-crosslinked cellulose composite hydrogel for an electrode material of stretchable TENG. Meanwhile, the in-situ polymerization of pyrrole endowed the hydrogel with satisfactory conductivity of 0.40 S/m. More impressively, the synergies of the cellulose rigid skeleton and the construction of the dual-crosslinking network significantly improved the mechanical toughness, and the hydrogel exhibited excellent self-strengthening through cyclic compression mechanical training, the self-strengthening efficiency reached 124.7 % after 10 compression cycles. Given these features, the hydrogel was used as wearable strain sensors with extremely high sensitivity (GF = 3.95) for real-time monitoring human motions. Additionally, the hydrogel showed practical applications in stretchable H-TENG for converting mechanical energy into electric energy to light LEDs and power a digital watch, and in self-powered wearable sensors to distinguish human motions and English letters. This work provided a promising strategy for fabricating sustainable, eco-friendly energy harvesting and self-powered electronic devices.

Ultrastretchable Triboelectric Nanogenerators Based on Ecoflex/Porous Carbon for Self‐Powered Gesture Recognition (Adv. Mater. Technol. 9/2023)

Triboelectric Nanogenerators In article number 2201769, Huamin Chen and co-workers present an ecoflex/porous carbon-based triboelectric nanogenerator (TENG) that exhibits ultrahigh stretchability and high performance due to the appropriate conductive networks and strong trapping effect. Its performance just degrades about 30% at a stretching strain of 177%. The stretchable TENG array can recognize gesture signal of the finger to control mechanical hand, which demonstrates a promising potential in human-machine interaction.

Single-Electrode Triboelectric Nanogenerators Based on Ionic Conductive Hydrogel for Mechanical Energy Harvester and Smart Touch Sensor Applications

Recent advancements in wearable electronic technology demand advanced power sources to be flexible, deformable, durable, and sustainable. An ionic-solution-modified conductive hydrogel-based triboelectric nanogenerator (TENG) has advantages in wearable devices. However, fabricating a conductive hydrogel with better mechanical and electrical properties is still a challenge. Herein, a simple approach is developed to insert ion-rich pores inside the hydrogel, followed by ionic solution soaking. The suggested ionic conductive hydrogel is obtained by cross-linking the polyvinyl alcohol (PVA) hydrogel and carboxymethyl cellulose sodium salt (CMC), followed by soaking in the ionic solution. Furthermore, a flexible and shape-adaptable single-electrode TENG (S-TENG) is fabricated by combinations of ionic-solution-modified dual-cross-linked CMC/PVA hydrogel and silicone rubber. Additionally, the effects of the CMC concentration, type of ionic solution, and concentration of optimized ionic solutions on the hydrogel properties and S-TENG output performance are studied systematically. The well-dispersed CMC- and PVA-based hydrogel provides ion-rich pores with high ion migration, leading to enhanced conductivity. The fabricated S-TENG delivers maximum output performance in terms of voltage, current, and charge density of ∼584 V, 25 μA, and 120 μC/m2, respectively. The rectified S-TENG-generated energy is used to charge capacitors and to power a portable electronic display. In addition to energy harvesting, the S-TENG is successfully demonstrated as a touch sensor that can automatically control the light and the speaker based on human motions. This investigation provides a deep insight into the influence of the hydrogel on the device performance and gives a guidance for designing and fabrication of highly flexible and stretchable TENGs.

Liquid‐Metal‐Based Stretchable Triboelectric Nanogenerators for Flowing‐Liquid‐Based Energy Harvesting and Self‐Powered Sensor Applications

AbstractIn this paper, a liquid‐metal‐based triboelectric nanogenerator (LM‐TENG) is proposed for harvesting energy from flowing water and self‐powered flow sensor applications. The proposed LM‐TENG mainly consists of a Galinstan working electrode that is encapsulated in a polydimethylsiloxane friction layer. The triboelectric performance of the LM‐TENG is optimized as a function of flow rate and frictional layer thickness. The output performance of the optimized LM‐TENG (6.2 V and 3.6 µA) is superior to that of the copper‐electrode‐based TENG (C‐TENG, 2.4 V and 0.8 µA) at the flow rate of 2.5 L min−1. This is because the stretchability of the optimized LM‐TENG is three times higher than that of the C‐TENG, which increases the contact area and enhances the output performance. The optimized LM‐TENG is successfully demonstrated as a self‐powered flow sensor for remote monitoring of water flow in pipelines. In addition, the LM‐TENG is a capable of powering more than 30 LEDs and directly powering low‐power electronics (LCDs).

Stretchable and self-healable conductive hydrogel-based multifunctional triboelectric nanogenerator for energy harvesting and dance motion sensing

Hydrogels with the integrated characteristics of adhesion, self-healing, deformability, and conductivity hold enormous potential for the design of next-generation flexible human body posture sensor and energy device. Here, we proposed a double-network hybrid polyacrylamide/poly(acrylic acid)/MXene/PEDOT:PET (PPMP) hydrogel with excellent flexibility, self-healing capabilities, and stability. Furthermore, the proposed PPMP conductive hydrogel with MXene/PDMS encapsulation layer can play the role of a wearable strain sensor that can be used to detect various dance movement postures, including those of facial expressions, blinking, and elbow joints. Additionally, the proposed PPMP hydrogel with MXene/PDMS encapsulation layer can function as a flexible and stretchable triboelectric nanogenerator (FS-TENG) to harvest human motion energy. The FS-TENG can obtain an open-circuit voltage (Voc) of 169.2 V and a short-circuit current (Isc) of 9.6 µA. Moreover, the electric energy generated by these FS-TENGs can be used to drive hygrothermographs. This research offers a feasible strategy to design self-powered strain sensors for use in dance posture monitoring and energy harvesting in human motion.

Electret elastomer-based stretchable triboelectric nanogenerators with autonomously managed power supplies for self-charging systems

Stretchable power sources capable of accommodating large deformations are urgently demanded for various stretchable and wearable electronics. In this work, we report a stretchable electret-based triboelectric nanogenerator (SEB-TENG) consisting of elastomeric electret as electrification materials and organo-hydrogels as electrodes. The electret elastomer, prepared by uniformly dispersing SiO2 nanoparticles in the elastomer matrix and thermally injecting static charges, obtains a high surface potential, high tensile strain (796%), and long stability. Then, the SEB-TENG device also achieves high stretchability (423%) and high charge density (0.2 mC m−2). Furthermore, a power management module (PMM) is designed to maximize the energy utilization of the SEB-TENG. The integrated self-charging system can be sufficiently used to constantly power a watch, or charge a Li-ion coin cell which subsequently provides sustainable power supplies to a digital thermometer. This work provides a viable approach to simultaneously achieve high output performances and high stretchability of integrated power sources.

Self-healable, stretchable triboelectric nanogenerators based on flexible polyimide for energy harvesting and self-powered sensors

Self-healing triboelectric nanogenerators (TENGs) are new, stable and durable energy harvesters. Polyimide (PI) is a promising negatively charged material that has been widely developed as a negative friction material for TENGs, but self-healing PI-based TENGs are currently vacant. Here, we reported a self-healing TENG device fabricated by self-healing PI for energy harvesting and motion sensing. The designed and fabricated PI-based TENGs exhibited excellent intrinsic self-healing and shape tailorability properties. The self-healing properties are derived from the dynamic disulfide bond exchange and flexible PDMS fragments in the PI backbone, which can recover its damage and output performance at 100 °C for 3 h. The output performance of the fabricated 6FDA-4PDA-PDMS-PI-based TENG was double that of the normal PI-based TENG due to CF3 electron-absorbing groups and siloxane fragments in the PI backbone. Finally, the applications of self-healing PI-based TENGs to harvest energy to drive commercial electronic devices and joint motion sensing were demonstrated. This work provides theoretical guidance for the fabrication of self-healing TENGs with reliable output performance and practical applications, contributing to the future of sustainable energy and wearable electronics.

A highly stretchable triboelectric nanogenerator with both stretch-insensitive sensing and stretch-sensitive sensing

It is an inevitable requirement for stretchable triboelectric nanogenerators to be able to sense external mechanical forces and convert them into observable electrical signals under adverse conditions (twisting, stretching, etc.). However, the vast majority of existing stretchable triboelectric nanogenerators have an inherent limitation that they cannot obtain stable contact triboelectric response under stretching deformation. Here, we propose a highly stretchable dual-mode triboelectric nanogenerator (SDTENG) with both stretch-insensitive sensing and stretch-sensitive sensing properties. By the regional modulus modulation based on cross-linked interpenetrating network (IPN), our SDTENG shows almost the same pressure sensing property represented by the triboelectric output in the 120% stretch range, mainly because the effective contact region of the friction layer is high modulus and stretch-unperturbed. While in the low modulus region, the MXene/CNT electrode of SDTENG exhibits excellent strain sensitivity with the stretching of the device, and the gauge factor is up to 238.8. The combination of stretch-insensitive pressure sensing and stretch-sensitive strain sensing makes our SDTENG with promising potential applications in wearable devices and smart robots.

A flexible and stretchable triboelectric nanogenerator based on a medical conductive hydrogel for biomechanical energy harvesting and electronic switches.

With the development of intelligent wearable electronic products, new requirements are put forward for large-scale production and durable power supplies and sensors. Herein, a flexible and stretchable single-electrode triboelectric nanogenerator (TENG) based on a medical conductive hydrogel (MCH) has been fabricated for biomechanical energy harvesting and electronic switches. The obtained MCH-TENG encapsulated by silicone rubber as an electrification layer demonstrated high electrical output performances. The size of the fabricated MCH-TENG was 40 × 60 mm2, which can generate an open-circuit voltage of 400 V, a power density of 444.44 mW m-2, and power 240 LEDs in series at a contact frequency of 3.0 Hz. The device can act not only as a power supply to drive electronic devices, but also as an energy collector to collect the energy of human movements. Particularly, as an electronic switch, the device enabled a high current amplification through the Darlington transistor circuit. Consequently, this work provides a new perspective of flexible and stretchable MCH-TENGs for wearable electronic devices.

Interfacial Roughness Enhanced Gel/Elastomer Interfacial Bonding Enables Robust and Stretchable Triboelectric Nanogenerator for Reliable Energy Harvesting.

Gel-based triboelectric nanogenerator (TENG) has demonstrated promising potentials in stretchable electronics owing to gel electrodes' intrinsic softness, stretchability, and conductivity. However, delamination between gel and elastomer layers in deformations remains a considerable challenge for gel-based TENG, which most often induces structure failure. Herein, gels are regarded as adhesives and further effectively enhances interfacial bonding strength by a rough interface in adhesives' view, which exploits gels' liquid-to-solid transformation. This method just needs surface roughness of elastomer, which avoids chemical modification. Moreover, this method is effective to both organogel with good stickiness and hydrogel with weak stickiness, demonstrating wide applicability to different gels. Owing to the tough gel/elastomer interfacial bonding, TENG-Rough largely solves delamination problem under various deformations and the corresponding output performances of TENG-Rough are also maintained, implying a robust stretchable TENG device for reliable energy harvesting. This work demonstrates a general and facile method to enhance interfacial bonding in an adhesives' way, which provides a view for addressing delamination problem in gel-based TENGs and other kinds of gel-based devices.

Stretching-insensitive stretchable and biocompatible triboelectric nanogenerators using plasticized PVC gel and graphene electrode for body-integrated touch sensor

Triboelectric nanogenerators (TENG) can generate strong electrical signals even with low frequencies and weak forces, thus research has been conducted to use them as wearable, body-attachable, and body-embeddable devices using biomechanical energies. For this reason, the TENG components, such as dielectric materials and electrodes, should be stretchable. A stretchable and biocompatible single electrode TENG based on plasticized polyvinyl chloride (PVC) gel with a graphene electrode is fabricated. PVC gel is a suitable stretchable TENG dielectric material owing to its high stretchability, dielectric constant, and tribo-negative properties, and graphene is a highly conductive electrode. Graphene and PVC gel-based stretchable and biocompatible TENGs display excellent electrical outputs (48 V, 2.5 μA, and 0.49 W/m2). The electrical resistance range of the electrode which does not affect the TENG output performance, and a stretching-insensitive TENG with approximately 50% stretching rate is successfully demonstrated through this study. In addition, both PVC gel and graphene are biocompatible. These stretching-insensitive and biocompatible TENGs may be used as a self-powered touch sensor that can be integrated into the human body.

A stretchable, self-healing and semi-transparent nanogenerator for energy harvesting and sensing

Triboelectric nanogenerators (TENGs) with an ability to harvest mechanical energy from natural and human activities, have shown tremendous potential to realise self-powered electronic devices and sensors. However, in order for optimum utilization of biomechanical energy, TENGs need to have body or tissue mimicking properties without compromising performance. Herein, a new hydrogel based all-soft, self-healing and stretchable TENG is introduced which exhibits outstanding power generation capability surpassing existing competitors. This unique TENG is realized by using gold nanoparticles doped semi-transparent hydrogel as an electrode and Ecoflex as the triboelectric layer which integrates multifunctional properties including rapid self-healing in < 2 min, 900% stretchability, high conductivity, transparency and excellent biocompatibility with human dermal fibroblasts. The use of a gel electrode with both ionic and electronic conductivities underlines the importance of gold nanoparticles in enhancing the performance of soft TENGs. A 5 cm2 device exhibits a prodigious power density of 1680 mWm−2 with an energy conversion efficiency of ≈ 26%, which is the highest achieved so far in contemporary hydrogel based TENGs. The moldable components allow easy fabrication of devices with tunable shapes and sizes that conforms to the human body and can power multiple electrical devices directly from body movements thus opening up possibilities for next generation self-powered wearable or implanted devices.

Skin-integrated, stretchable triboelectric nanogenerator for energy harvesting and mechanical sensing

Due to the potential application of wearable electronics in human medical treatment and human machine interfaces, extensive investigations and research have been conducted recently. To provide sufficient and continuous power to the state-of-art flexible electronics, many wearable self-powered technologies have been developed. Triboelectric nanogenerators (TENGs) provide a prospective alternative option to efficiently transform mechanical energy during human daily movement into electricity, which can be utilized for motion capturing and energy harvesting. Here, we have developed a thin, skin-integrated stretchable triboelectric nanogenerator based on the contact-separation mode through a low-cost fabrication process. By adopting the serpentine designed Cu electrodes, the device has exhibited excellent flexibility and stretchability. To separate the two triboelectric layers, a flexible pillar array is built in the middle by screening printing, realizing the thin format of the TENG. Due to mechanical design, the TENG exhibits a wide pressure sensing range from ∼ 8.125 kPa to ∼ 43.125 kPa, corresponding to the open-circuit voltages ranging from ∼ 10 V to ∼ 80 V, allowing sensing to various external pressures, such as finger touching, tapping, and punching. At the external pressure of 43.125 kPa, the power output of the TENG could reach up to 300 μW/cm 2 . Under a constant tapping by fingers, the energy yielded by the device could light 40 LEDs. Furthermore, a 4 × 4 arrayed TENG-based pressure sensor was further fabricated and demonstrates its potential applications in human motion monitoring and tactile mapping.