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Triboelectric nanogenerator (TENG) provides a new cost‐effective strategy to harvest water wave energy due to the broad options of triboelectric materials and the high efficiency in low‐frequency energy harvesting. Here, a new triboelectric–electromagnetic hybrid nanogenerator (TEHG) consisting of a soft ball‐based triboelectric nanogenerator (SB‐TENG) and an electromagnetic generator (EMG) is reported for harvesting wave energy. The soft balls are utilized as one triboelectric layer to increase the contact area with the copper electrodes. The critical parameters that may affect the energy harvesting performance of the SB‐TENG are investigated, including the type of the filled liquids, the thickness of the silicone shell, the number of layers, and the added soft balls. Under an operating frequency of 1 Hz, the SB‐TENG and the EMG can reach a maximum output peak power of 0.5 and 8.5 mW, respectively. The TEHG has been demonstrated to power dozens of light‐emitting diodes and drives a digital temperature sensor to monitor the water temperature for an extended period. This study provides a new design and approach to improve the output performance of TENGs and presents an excellent prospect for building a self‐powered water‐sensing system driven by low‐frequency water waves. [ABSTRACT FROM AUTHOR]

Innovative human–machine interfaces (HMIs) have attracted increasing attention in the field of system control and assistive devices for disabled people. Conventional HMIs that are designed based on the interaction of physical movements or language communication are not effective or appliable to severely disabled users. Here, a breath‐driven triboelectric sensor is reported consisting of a soft fixator and two circular‐shaped triboelectric nanogenerators (TENGs) for self‐powered respiratory monitoring and smart system control. The sensor device is capable of effectively detecting the breath variation and generates responsive electrical signals based on different breath patterns without affecting the normal respiration. A breathing‐driven HMI system is demonstrated for severely disabled people to control electrical household appliances and shows an intelligent respiration monitoring system for emergence alarm. The new system provides the advantages of high sensitivity, good stability, low cost, and ease of use. This work will not only expand the development of the TENGs in self‐powered sensors, but also opens a new avenue to develop assistive devices for disabled people through innovation of advanced HMIs. [ABSTRACT FROM AUTHOR]

Multifunctional metamaterials (MFMs) capable of energy harvesting and vibration control are particularly attractive for smart structures, wearable/biointegrated electronics, and intelligent robotics. Here, a novel MFM based on triboelectric nanogenerators (TENGs), which can harvest environmental energy and reduce vibration simultaneously, is reported. The unit cells of the MFM consist of a local resonator, an integrated contact‐ separation mode TENG, and spiral‐shaped connecting beams. A multiphysics theoretical model is developed for quantitatively evaluating the performance of the MFM by including the mechanical and electrical fields interactions, which is further validated by experimental testing. It is demonstrated that the TENG‐based MFM can not only effectively harvest vibration energy to power electronics but also dramatically suppress low‐frequency mechanical vibration. This work provides a new design and model for developing novel TENG‐based MFMs for advanced smart systems used in a variety of applications. [ABSTRACT FROM AUTHOR]

Soft robots have attracted great attention in the past decades owing to their unique flexibility and adaptability for accomplishing tasks via simple control strategies, as well as their inherent safety for interactions with humans and environments. Here, a soft robotic manipulation system capable of stiffness variation and dexterous operations through a remotely controlled manner is reported. The smart manipulation system consists of a soft omnidirectional arm, a dexterous multimaterial gripper, and a self‐powered human–machine interface (HMI) for teleoperation. The cable‐driven soft arm is made of soft elastomers and embedded with low melting point alloy as a stiffness‐tuning mechanism. The self‐powered HMI patches are designed based on the triboelectric nanogenerator that utilizes a sliding mode of tribo‐layers made of copper and polytetrafluoroethylene. The novel soft manipulation system has great potential for soft and remote manipulation and human machine interactions in a variety of applications from elderly care to surgical operation to agriculture harvesting. [ABSTRACT FROM AUTHOR]

Forest fires present a great threat as they can rapidly grow and become large, resulting in tragic loss of life and property when occurring near occupied land. Here a self‐powered fire alarm system based on a novel multilayered cylindrical triboelectric nanogenerator (MC‐TENG) that can produce electrical power for the detection sensors by harvesting the kinetic energy of moving tree branches in a forest is presented. The major parameters for harvesting the kinetic energy using the proposed MC‐TENG are investigated, including the number of triboelectric layers, the frequency, the amplitude of external excitation, and the orientation between motion direction and device configuration. The fabricated MC‐TENG results in a peak power of 2.9 mW and a maximum average power of 1.2 mW at a low frequency of 1.25 Hz. The integrated self‐powered forest fire alarm system, consisting of fire sensors, a carbon‐based micro‐supercapacitor, and the MC‐TENG, is demonstrated to be able to report fire risk or hazard efficiently, accurately, and robustly. This study provides a new solution to reduce the forest fire risk through a portable and sustainable alarm system by effectively harvesting kinetic energies in natural environment with TENG technology. [ABSTRACT FROM AUTHOR]

Soft end effectors or grippers capable of grasping objects dexterously and efficiently have attracted increasing attention in a broad range of applications. This article describes a smart soft finger‐like actuator with fast response, accurate control, self‐powered pressure, and bending sensing capability by combing the cable‐driven actuation with soft triboelectric nanogenerators (TENGs). The soft actuator, driven by a miniature DC motor, is designed to have multiple segments of elastomer body split with triangular cuts to facilitate the bending actuation and conformal contact with target objects. Two types of TENGs are integrated with the soft actuator: a single‐electrode‐mode TENG to measure the contact pressure and an inner contact–separation‐mode TENG to detect the bending. With micropyramid structures, the tribo‐skin patches possess high sensitivity and good compatibility with the actuator and can actively detect proximity, contact, and pressure via self‐generated electricity. Based on the modular design approach, a gripper with three fingers is fabricated and tested for its grasping, sensing, and self‐powering performance. This gripper is capable of picking up different kinds of objects, providing sensory feedback, and generating electricity, which shows great potential for use in robot–human and robot–environment interaction applications. [ABSTRACT FROM AUTHOR]

To meet the great need for distributed and sustainable power sources, mechanical energy in the environment is widely used for electricity generation. Based on the coupling effect of triboelectrification and electrostatic induction, triboelectric nanogenerator (TENG) as an innovative energy technology has advantages of collecting fluctuating amplitude and low-frequency mechanical energy. In this paper, a leaf-shaped TENG has been demonstrated to harvest multiple ambient mechanical energy. By the characterization with different mechanical energy sources, the leaf-shaped TENG has been proven as an effective tool to scavenge wind, vibration, and falling raindrop energy. Furthermore, based on numerous leaf-shaped TENGs, a leaf-shaped TENG tree has been developed, which can be used for continuous collection of environmental mechanical energy at large-scale. This paper has first exhibited a conformal structure for simultaneously harvesting various mechanical energy, which has bright potentials in environmental monitoring, Internet of things, and wireless sensor networks. [ABSTRACT FROM AUTHOR]

Abstract: The air breakdown phenomenon is generally considered as a negative effect in previous research on triboelectric nanogenerators (TENGs), which is always accompanied by air ionization. Here, by utilizing the air breakdown induced ionized air channel, a direct‐current triboelectric nanogenerator (DC‐TENG) is designed for harvesting contact‐separation mechanical energy. During working process, the charges first transfer from bottom to top electrodes through an external circuit in contact state, then flow back via the ionized air channel created by air breakdown in the separation process. So a unidirectional flow of electrical charges can be observed in the external circuit. With repeating contact‐separation cycles, continuous pulsed DC output through the external circuit can be realized. This working mechanism was verified by real‐time electrode potential monitoring, photocurrent signal detection, and controllable discharging observation. The DC‐TENG can be used for directly and continuously charging an energy storage unit and/or driving electronic devices without using a bridge rectifier. Owing to its simplicity in structure, the mechanism is further applied to fabricate the first flexible DC‐TENG. This research provides a significant fundamental study for DC‐TENG technology and may expand its application in flexible electronics and flexible self‐charging power systems. [ABSTRACT FROM AUTHOR]

Abstract: Liquid metals (LMs) have attracted great attentions in electronics for great interface contact and flowability. Here, an LM‐gated tribotronic transistor (LMTT) is demonstrated, in which an electrostatic potential is created through the triboelectrification of LM and dielectric layer, and the carrier transport between drain and source can be tuned by the swing‐induced electrostatic potential instead of the traditional gate voltage. Based on the fabricated LMTTs, an electronic gradienter is developed, which can be used for angle measurement and exhibits a great sensitivity, large sensing range, and excellent stability. This work has first introduced the LM into the tribotronic device, which may have potential applications in mechanical calibration, civil engineering, and geologic exploration. [ABSTRACT FROM AUTHOR]

Abstract: Growing demand in automobile safety system raises a requirement to electronic devices being self‐powered, stable, and durable. Herein, a self‐powered Hall vehicle sensor (SPHVS) is demonstrated for automobile safety system, which integrates the triboelectric nanogenerator, the management circuit, the magnet, and the Hall element. The tribotronic constant current source is proposed to steadily power the Hall element in rotational motion at any different speeds. Furthermore, the performances of the SPHVS for vehicle speed sensing and vehicle braking monitoring are systematically investigated, which exhibits wide sensing range, great stability, and excellent sensitivity. This work clearly proposes a promising solution for speed sensing and braking monitoring, and indicates the potential applications of power tribotronics for the self‐powered electronic devices in prospective automobile industry. [ABSTRACT FROM AUTHOR]

A novel tribotronic transistor has been developed by vertically coupling a single-electrode mode triboelectric nanogenerator and a MoS2 field effect transistor. Once an external material contacts with or separates from the device, negative charges are induced by triboelectrification on the surface of the polymer frictional layer, which act as a 'gate' voltage to modulate the carrier transport in the MoS2 channel instead of the conventional applied gate voltage; the drain-source current can be tuned in the range of 1.56-15.74 μA, for nearly ten times. The application of this MoS2 tribotronic transistor for the active smart tactile switch is also demonstrated, in which the on/off ratio can reach as high as ≈16 when a finger touches the device and the increased drain-source current is sufficient to light two light-emitting diodes. This work may provide a technique route to utilize the 2D materials based tribotronic transistors in MEMS, nanorobotics, and human-machine interfacing. [ABSTRACT FROM AUTHOR]

The triboelectric nanogenerator (TENG) is a promising mechanical energy harvesting technology, but its pulsed output and the instability of input energy sources make associated energy‐storage devices necessary for real applications. In this work, feasible and efficient charging of Li‐ion batteries by a rotating TENG with pulsed output current is demonstrated. In‐depth discussions are made on how to maximize the power‐storage efficiency by achieving an impedance match between the TENG and a battery with appropriate design of transformers. With a transformer coil ratio of 36.7, ≈72.4% of the power generated by the TENG at 250 rpm can be stored in an LiFePO4–Li4Ti5O12 battery. Moreover, a 1 h charging of an LiCoO2–C battery by the TENG at 600 rpm delivers a discharge capacity of 130 mAh, capable of powering many smart electronics. Considering the readily scale‐up capability of the TENG, promising applications in personal electronics can be anticipated in the near future. [ABSTRACT FROM AUTHOR]

Grippers, human-machine interfaces, motion sensors, soft arms, soft robotics, triboelectric nanogenerators, variable stiffness Keywords: grippers; human-machine interfaces; motion sensors; soft arms; soft robotics; triboelectric nanogenerators; variable stiffness EN grippers human-machine interfaces motion sensors soft arms soft robotics triboelectric nanogenerators variable stiffness 1 1 1 05/07/21 20210501 NES 210501 In article number 2100084, Changyong Cao and co-workers develop a novel soft robotic manipulation system capable of stiffness variation and dexterous operation for safe human-machine interactions. Human-Machine Interfaces: Soft Robotic Manipulation System Capable of Stiffness Variation and Dexterous Operation for Safe Human-Machine Interactions (Adv. [Extracted from the article]

Additive manufacturing, i.e., 3D printing, is being increasingly utilized to fabricate a variety of complex‐shaped electronics and energy devices (e.g., batteries, supercapacitors, and solar cells) due to its excellent process flexibility, good geometry controllability, as well as cost and material waste reduction. In this review, the recent advances in 3D printing of emerging batteries are emphasized and discussed. The recent progress in fabricating 3D‐printed batteries through the major 3D‐printing methods, including lithography‐based 3D printing, template‐assisted electrodeposition‐based 3D printing, inkjet printing, direct ink writing, fused deposition modeling, and aerosol jet printing, are first summarized. Then, the significant achievements made in the development and printing of battery electrodes and electrolytes are highlighted. Finally, major challenges are discussed and potential research frontiers in developing 3D‐printed batteries are proposed. It is expected that with the continuous development of printing techniques and materials, 3D‐printed batteries with long‐term durability, favorable safety as well as high energy and power density will eventually be widely used in many fields. [ABSTRACT FROM AUTHOR]

The front cover page of the journal is presented.

Extrusion-based 3D printing is a facile technology to construct complex structures of hydrogels, especially for tough hydrogels that have shown demonstrated potential in load-bearing materials and tissue engineering. However, 3D-printed hydrogels often possess mechanical properties that do not guarantee their usage in tissue-mimicking, load-bearing components, and motion sensors. This study proposes a novel strategy to construct high-strength and anisotropic Fe 3+ cross-linked poly(acrylamide-co-acrylic acid)/sodium alginate double network hydrogels. The semi-flexible sodium alginate chains act as a "conformation regulator" to promote the formation of strong intermolecular interactions between polymer chains and lock the more extended conformation exerted by the pre-stretch, enabling the construction of 3D-printed hydrogel structures with high orientation. The equilibrated anisotropic hydrogel filaments with a water content of 50-60 wt.% exhibit outstanding mechanical properties (tensile strength: 9-44 MPa; elongation at break: 120-668%; Young's modulus: 7-62 MPa; toughness: 26-52 MJ m - 3 ). 3D-printed anisotropic hydrogel structures with high mechanical performance show demonstrated potential as loading-bearing structures and electrodes of flexible triboelectric nanogenerators for versatile human motion sensing., (© 2024 Wiley‐VCH GmbH.)

Stretchable electronics are of great significance for the development of the next-generation smart interactive systems. Here, we propose an intrinsically stretchable organic tribotronic transistor (SOTT) without a top gate electrode, which is composed of a stretchable substrate, silver nanowire electrodes, semiconductor blends, and a nonpolar elastomer dielectric. The drain-source current of the SOTT can be modulated by external contact electrification with the dielectric layer. Under 0-50% stretching both parallel and perpendicular to the channel directions, the SOTT retains great output performance. After being stretched to 50% for thousands of cycles, the SOTT can survive with excellent stability. Moreover, the SOTT can be conformably attached to the human hand, which can be used for tactile signal perception in human-machine interaction and for controlling smart home devices and robots. This work has realized a stretchable tribotronic transistor as the tactile sensor for smart interaction, which has extended the application of tribotronics in the human-machine interface, wearable electronics, and robotics., Competing Interests: The authors declare no competing interests., (Copyright © 2020 Junqing Zhao et al.)

The development of stretchable electronics requires the invention of compatible high-performance power sources, such as stretchable supercapacitors and batteries. In this work, two-dimensional (2D) titanium carbide (Ti 3 C 2 T x ) MXene is being explored for flexible and printed energy storage devices by fabrication of a robust, stretchable high-performance supercapacitor with reduced graphene oxide (RGO) to create a composite electrode. The Ti 3 C 2 T x /RGO composite electrode combines the superior electrochemical and mechanical properties of Ti 3 C 2 T x and the mechanical robustness of RGO resulting from strong nanosheet interactions, larger nanoflake size, and mechanical flexibility. It is found that the Ti 3 C 2 T x /RGO composite electrodes with 50 wt % RGO incorporated prove to mitigate cracks generated under large strains. The composite electrodes exhibit a large capacitance of 49 mF/cm 2 (∼490 F/cm 3 and ∼140 F/g) and good electrochemical and mechanical stability when subjected to cyclic uniaxial (300%) or biaxial (200% × 200%) strains. The as-assembled symmetric supercapacitor demonstrates a specific capacitance of 18.6 mF/cm 2 (∼90 F/cm 3 and ∼29 F/g) and a stretchability of up to 300%. The developed approach offers an alternative strategy to fabricate stretchable MXene-based energy storage devices and can be extended to other members of the large MXene family.

Owing to the perfect combination of metallic conductivity, liquid fluidity, and mechanical stability, liquid metals (LMs) are considered the potential materials of the electromechanical system and the basic components of liquid robot. Here, triboelectric effect-driven liquid metal actuators (TLMAs) have been demonstrated, in which the motions of LMs could be driven and accurately controlled by triboelectric nanogenerators (TENGs). By the coulomb forces of transferred triboelectric charges in interdigital electrodes and inertia effects, the LM could be driven for continuous linear and circular motions, respectively. As an alternative structure, the motion of LMs could also be accurately controlled, in which the reciprocating and merging of LMs have been demonstrated. Moreover, the TLMA could serve as a control switch to modulate on/off of an LED by integrating into a circuit, and a transport system based on TLMA has also been demonstrated. In this work, the TENG is used as a medium to first drive and accurately control LMs by external mechanical force, which may have great applications in Micro-Electro-Mechanical System (MEMS), liquid robot, and intelligent microcontroller.

Electric double layers (EDLs) formed in electrolyte-gated field-effect transistors (FETs) induce an extremely large local electric field that gives a highly efficient charge carrier control in the semiconductor channel. To achieve highly efficient triboelectric potential gating on the FET and explore diversified applications of electric double layer FETs (EDL-FETs), a triboiontronic transistor is proposed to bridge triboelectric potential modulation and ion-controlled semiconductor devices. Utilizing the triboelectric potential instead of applying an external gate voltage, the triboiontronic MoS 2 transistor is efficiently operated owing to the formation of EDLs in the ion-gel dielectric layer. The operation mechanism of the triboiontronic transistor is proposed, and high current on/off ratio over 10 7 , low threshold value (75 μm), and steep switching properties (20 µm dec -1 ) are achieved. A triboiontronic logic inverter with desirable gain (8.3 V mm -1 ), low power consumption, and high stability is also demonstrated. This work presents a low-power-consuming, active, and a general approach to efficiently modulate semiconductor devices through mechanical instructions, which has great potential in human-machine interaction, electronic skin, and intelligent wearable devices. The proposed triboiontronics utilize ion migration and arrangement triggered by mechanical stimuli to control electronic properties, which are ready to deliver new interdisciplinary research directions., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Piezoelectric organic-inorganic lead halide perovskites have recently attracted much attention in the field of optoelectronic devices. However, their piezoelectric properties as a possible way to modulate device performances have rarely been reported. Here, we study experimentally a photodetector based on CH 3 NH 3 PbI 3 (MAPbI 3 ) single crystals, whose performance is effectively modulated via an emerging effect-the piezo-phototronic effect, which is to use the piezoelectric polarization charges to tune the optoelectronic processes at the interface. A piezoelectric coefficient of 10.81 pm/V of the CH 3 NH 3 PbI 3 single crystal is obtained. Under 680 nm laser illumination with a power density of 3.641 mW/cm 2 and at an external bias of 2 V, compared to the case without straining, the light current of the photodetector is enhanced by ∼120% when a 43.48 kPa compressive pressure is applied. The response speed of the photocurrent is 3 and 2 times faster than the cases without applying pressure for the light-on and light-off states, respectively. This work proves that the performance of the photodetector based on MAPbI 3 single crystals can be effectively enhanced by the piezo-phototronic effect, providing a good method for optimizing the performance of future perovskite-based optoelectronic devices.

Because silicon transistors are rapidly approaching their scaling limit due to short-channel effects, alternative technologies are urgently needed for next-generation electronics. Here, we demonstrate ultrathin ZnO piezotronic transistors with a ∼2 nm channel length using inner-crystal self-generated out-of-plane piezopotential as the gate voltage to control the carrier transport. This design removes the need for external gate electrodes that are challenging at nanometer scale. These ultrathin devices exhibit a strong piezotronic effect and excellent pressure-switching characteristics. By directly converting mechanical drives into electrical control signals, ultrathin piezotronic devices could be used as active nanodevices to construct the next generation of electromechanical devices for human-machine interfacing, energy harvesting, and self-powered nanosystems.