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Droplet-based triboelectric nanogenerators (D-TENGs) have recently gained much attention due to their great potential in harvesting energy. However, the output performance of conventional single-electrode droplet-based TENGs is limited owing to low induced electrification efficiency. The asymmetric distribution of electric fields on both sides of the electrode edge enhances the electrostatic induction process and improves the output performance of D-TENG. Herein, an induced electrification-enhanced droplet-based triboelectric nanogenerator (IED-TENG) is developed to effectively enhance the output performance by simultaneously optimizing the electrode structure and the dynamics of the water droplet. One droplet falling from a height of 30 cm results in a -70 V output voltage and -6 µA short-circuit current, which is 70 times and 20 times the full-inductive-electrode mode, respectively. The working principle and the relationship between electric signal and droplet dynamics are analyzed in detail. Moreover, the peak output voltage can reach -110 V, and the peak current can get -140 µA by using the power generation of multiple water droplets. The present protocol provides an easy and reproducibility strategy in energy harvesting and sensing areas.

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The recent application of the internet of things demands the ubiquitous utilization of data and electrical power. Even with the development of a wide variety of energy-harvesting technologies, few studies have reported a device transporting electrical energy and data simultaneously. This paper reports an electrostatic induction nanogenerator (ESING) consisting of a one-dimensional metastructure that can modulate the output voltage based on the resonance of ultrasound waves to transmit energy and data simultaneously. The ESING device is fabricated using electronegative poly(vinylidene fluoride) (PVDF) membrane using a phase inversion process. The output voltage from the ESING device exhibits periodic resonant peaks as the gap between the PVDF membrane and the Al electrode changes, showing an up to 35-fold difference between the maximum and minimum output voltages depending on the resonance state. The energy and electrical signal can be transmitted simultaneously in free space because the ESING converts energy from high-frequency ultrasound waves. This paper provides proof of concept for a data and energy-transferable smart tag device based on ESING devices exhibiting resonant and non-resonant states. A device consisting of four ESINGs for a 4-bit signal is implemented to demonstrate 16 signals.

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Traditional alternating current (AC) and direct current (DC) triboelectric nanogenerators (TENGs), which are implemented via the pairwise coupling of triboelectrification, electrostatic induction, and electrostatic discharge, have been widely explored in various fields. In this work, the comprehensive integration and synergetic utilization of triboelectrification, electrostatic induction, and electrostatic discharge in a single device for the first time is realized, achieving a dual-functional TENG (DF-TENG) to produce an AC/DC convertible output. Distinguishing from the conventional TENGs, the coupling of triboelectrification and electrostatic discharge enables charge circulation between the dielectric tribo-layers, while electrostatic induction realizes charge transfer in the external circuit. This novel energy conversion mechanism has been proven to be applicable to a variety of materials, including polymers, fabrics, and semiconductors. The output mode of the DF-TENG can be tuned by adjusting the slider motion state, and its constant output current and power density can reach 1.51 mA m-2 Hz-1 and 398 mW m-2 Hz-1 , respectively, which are the highest records reported for constant DC-TENGs to date. This work not only provides a paradigm shift to achieve AC/DC convertible output, but it also exhibits high potential for extending the TENG design philosophy.

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With WO3/BiVO4/MXene ternary composite layers as a working electrode, a smart volumetric photoelectrochemical system using electrostatic bias voltage inducted by atmospheric electric field was developed. Under single sun illumination and 0.8 V hardwired bias, the current response of the ternary electrode is 1.15 mA cm-2, which is 1.31 times higher than that of the WO3/BiVO4 electrode, mainly due to the higher charge transfer rate between the MXene layer and the BiVO4 structure. Further, the response of the ternary electrode increases to 1.39 mA cm-2 at an extra atmospheric electric field of 1100 V m-1. It can be demonstrated that the effect of the atmospheric electric field can be regarded as an extra hardwired bias of 0.101 V in the system. The experimental results reveal that the native carriers, including inducted electron/holes in MXene and BiVO4, and carriers in the electrolyte, are all effectively excited by the electrostatic induction of atmospheric electric field.

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This paper describes a non-contact and real-time measurement technique of human body potential using ultra-sensitive electrostatic induction. When a participant moves his/her palm to a position approximately 30 cm away from an electrostatic induction sensor, electrostatic induction current flows transiently. It is clarified whether estimation of the human body potential is possible by simultaneously measuring the velocity of the participant's palm and distance between the participant's palm and sensor. In addition, even when the participant walks at a position approximately 50 cm away from the electrostatic induction sensor, it is confirmed that the estimation of human body potential is possible.

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The ability to control the mobility and function of droplets is fundamental to developing open surface microfluidics. Despite notable progress in the manipulation of droplets, the existing strategies are still limited in functionalizing droplets. Herein, the coupling of droplet motion and functionalization elicited by an invisible charge wall is reported. The charged superamphiphobic surface is overlapped with a conductor to induce free charge, creating the invisible charge wall at the overlapping boundary. The charge wall can trap droplets and polarize them into Janus charged state. It is found that the trapping degree and the charge distribution in the Janus charged droplet depend on the original surface charge on the superamphiphobic surface. The invisible charge wall can also be established at diverse boundary curvatures, allowing to design pathways for droplet manipulations. Furthermore, the enrichment of protein and nanomaterial in the manipulated Janus charged droplet is demonstrated. The strategy provides a potential microfluidic platform with orthogonal functionalities.

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Sensors as the significant units of the Internet of Things play an important role in the field of information interaction. Non-contact sensors have the advantages of flexible manipulation and a longer lifespan but it is constrained in motion detection due to their relative single detection function. Herein, a self-powered non-contact motion vector sensor (NMVS) for the multifunctional human-machine interface is reported. Based on the electrostatic induction effect, the motion vector is measured according to the output electrical signals from the non-contact triboelectric nanogenerator (NC-TENG). By simulation analysis and experimental validation, the output characteristics of NC-TENG dependence on structural and motion parameters are investigated in detail. On this basis, the resolution of NMVS is improved and exhibits for non-contact micro-vibration monitoring, rehabilitation gait detection, contactless smart lock, and the non-contact limit alarm. This work not only proposes an ingenious strategy for non-contact motion vector detection but also demonstrates the promising prospects of a multifunctional human-machine interface in intelligent electronics, health rehabilitation, and industrial inspection.

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Various physical tweezers for manipulating liquid droplets based on optical, electrical, magnetic, acoustic, or other external fields have emerged and revolutionized research and application in medical, biological, and environmental fields. Despite notable progress, the existing modalities for droplet control and manipulation are still limited by the extra responsive additives and relatively poor controllability in terms of droplet motion behaviors, such as distance, velocity, and direction. Herein, we report a versatile droplet electrostatic tweezer (DEST) for remotely and programmatically trapping or guiding the liquid droplets under diverse conditions, such as in open and closed spaces and on flat and tilted surfaces as well as in oil medium. DEST, leveraging on the coulomb attraction force resulting from its electrostatic induction to a droplet, could manipulate droplets of various compositions, volumes, and arrays on various substrates, offering a potential platform for a series of applications, such as high-throughput surface-enhanced Raman spectroscopy detection with single measuring time less than 20 s.

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Soaring developments in wearable electronics raise an urgent need for stretchable electrets. However, achieving soft electrets simultaneously possessing excellent stretchability, longevity, and high charge density is still challenging. Herein, a facile approach is proposed to prepare an all-polymer hybrid composite electret based on the coupling of elastomer and ePTFE membrane. The composite electrets are fabricated via a facile casting and thermal curing process. The obtained soft composite electrets exhibit constantly high surface potential (-0.38 kV) over a long time (30 days), large strain (450%), low hysteresis, and excellent durability (15,000 cycles). To demonstrate the applications, the stretchable electret is utilized to assemble a self-powered flexible sensor based on the electrostatic induction effect for the monitoring of human activities. Additionally, output signals in the pressure mode almost two orders of magnitude larger than those in the strain mode are observed and the sensing mechanism in each mode is investigated.

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BACKGROUND: There is a need to develop a new device to evaluate and monitor the condition of human skin and make it possible to measure the skin in the diary because the current accuracy of water content measurement in the stratum corneum by capacitance and conductance measurement sensor that are used as the gold standard is insufficient. MATERIALS AND METHODS: The electrostatic sensor is composed of a thin silicone gum sheet and a copper film. In the experiment, skin conditions on six positions such as the forearm, upper arm, and face of a test subject before and after tape stripping are measured by the electrostatic sensor and a commercial sensor. Skin conditions on the forearm of five subjects before and after pasted distilled water were measured by their sensors. RESULTS: The voltages measured by the electrostatic sensor and moisture measured by a commercial sensor are increased with P < 0.01 before and after skin stripping. There were increases in the voltage and the moisture with P < 0.01 before and after pasted distilled water. CONCLUSION: It is suggested that it is possible to measure the moisture on the upper layer of the skin by the electrostatic sensor.

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This paper presents an ultra-low power hand gesture sensor using electrostatic induction for mobile devices. Two electrodes, which consist of electret foils stacked on metal sheets, are used to recognize two gestures such as hand movements from left to right and right to left. The hand gesture recognition is realized by detecting the electrostatic induction currents induced by hand movements. However, the electrostatic induction currents are significantly small; hence, a hand gesture recognition chip is first designed in this study to amplify and detect the small electrostatic induction currents with low power. This chip is fabricated in a commercial 180 nm complementary metal oxide semiconductor (CMOS) process, and the measurement results indicate that the fabricated gesture recognition chip consumes 406 nW, which is less than 1/100th of the power dissipation of conventional gesture sensors.

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Triboelectric nanogenerators (TENGs) are actively being researched and developed to become a new external power unit for various electronics and applications. Wind is proposed as a mechanical energy source to flutter the dielectric film in wind-driven TENGs as it is clean, abundant, ubiquitous, and sustainable. Herein, we propose a TENG structure with dielectric films bent in four directions to collect the wind energy supply from all directions, unlike the conventional wind-driven TENGs which can only harvest the wind energy from one direction. Aluminum (Al) layer was intercalated within the dielectric film to improve electrostatic induction, resulting in improved triboelectric performances. Maximum open-circuit voltage (Voc) of 233 V, short-circuit current (Isc) of 348 µA, and output power density of 46.1 W m- 2 at an external load of 1 MΩ under a wind speed of 9 m s- 1 were revealed, and it faithfully lit "LED" characters composed of 25 LEDs.

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Electrostatic nanogenerators or capacitive sensors that leverage electrostatic induction for power generation or sensing, has attracted significant interests due to their simple structure, ease of fabrication, and high device stability. However, in order for such devices to work, an additional power source or a post-charging process is necessary to activate the electrostatic effect. In this work, an electrostatic nanogenerator is fabricated using electrospun polystyrene (PS) mats and dip-coated graphene oxide (GO) films as the self-charged components. The electret performances of the PS mats and GO films are characterized via the electrostatic force microscopy phase shift and surface potential measurements. With a multilayer device structure that consists of top electrodes/GO films/spacer/electrospun PS mats/bottom electrodes, the resultant device acts as an electrostatic generator that operates in the noncontact mode. The nanogenerator can output a peak voltage of ca. 6.41 V and a peak current of ca. 6.57 nA at a rate of 1 Hz of mechanical compression, and with no attenuation of electrical outputs even after 50 000 cycles over a 13 h period. Furthermore, this as-prepared device is also capable of serving as a self-powered capacitive sensor for detection of tiny mechanical impacts and measurement of human finger bending. This results of this work provides a new avenue to easily fabricate electrostatic nanogenerators with high durability and self-powered capacitive sensors for the detection of small impacts.

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Triboelectric nanogeneration is a burgeoning and promising technology for harvesting low-frequency mechanical energy from the environment, but the energy conversion efficiency and service life of the triboelectric nanogenerator (TENG) device are limited by the inevitable frictional resistance between the tribo-surfaces. Herein, we propose an electrostatic induction nanogenerator (EING) circulation network (EICN) by integrating an arbitrary number of EING units for harvesting low-frequency mechanical energy. Because of absolute conquering of the friction resistance between the tribo-surfaces, the average power density of the EING device in the EICN by the initial charge injection (from a TENG or a power supply) is more than a 15-fold enhancement compared with the previous swing-structured TENG. The EICN can recover to the stable and optimal electrical output state in 90 s without external charge injection, even if the external triggering interrupts for 40 min and then restarts, demonstrating the excellent application feasibility of this strategy. To display the practical application scenario for harvesting large-scale mechanical energy from the environment, a high-performance and ultralow-friction TENG is designed for the initial charge injection to the EICN. Moreover, portable electronic devices are powered successfully to realize the self-powered sensing and remote marine environmental monitoring when an EICN with three EINGs is triggered by the real water wave. This EICN strategy not only can harvest low-frequency swing type mechanical energy but also has the capacity of harvesting the rotational mechanical energy after reasonable structure modification, providing an excellent candidate for large-scale blue energy harvesting in practical applications.

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The lack of a universal simulation method for triboelectric nanogenerator (TENG) makes the device design and optimization difficult before experiment, which protracts the research and development process and hinders the landing of practical TENG applications. The existing electrostatic induction models for TENGs have limitations in simulating TENGs with complex geometries and their dynamic behaviors under practical movements due to the topology change issues. Here, a dynamic finite element method (FEM) model is proposed. The introduction of air buffer layers and the moving mesh method eliminates the topology change issues during practical movement and allows simulation of dynamic and time-varying behaviors of TENGs with complex 2D/3D geometries. Systematic investigations are carried out to optimize the air buffer thickness and mesh densities, and the optimized results show excellent consistency with the experimental data and results based on other existing methods. It also shows that a 3D disk-type rotating TENG can be simulated using the model, clearly demonstrating the capability and superiority of the dynamic FEM model. Moreover, the dynamic FEM model is used to optimize the shape of the tribo-material, which is used as a preliminary example to demonstrate the possibility of designing a TENG-based sensor.

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Regulation of charge-transport direction is realized through the coupling of triboelectrification, electrostatic induction, and semiconducting properties for area-scalable conversion of mechanical energy. The output current from each unit triboelectric generator can always constructively add up due to the unidirectional flow of electrons. This work proposes a practical and general route to area-scalable applications of the triboelectric generator and other energy-harvesting techniques.

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Harvesting ambient mechanical energy from human body motion has attracted great research interest. In this work, a power shirt based on triboelectrification and the electrostatic induction effect between fluorinated ethylene propylene (FEP) and external objects is demonstrated. This power shirt can effectively convert the ambient mechanical energy into electric power, and the working mechanism is systematically discussed. A maximum short-circuit current density of ∼0.37 µA/cm2 and a maximum peak power density of ∼4.65 µW/cm2 were achieved. Simultaneously, 11 blue LEDs were lit by sliding the sleeve and power shirt, indicating the potential application of the power shirt in clothes ornamentation and risk warning. This study develops an efficient path for harvesting human body energy and promoting the development of wearable electronics and smart garments.

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Triboelectric nanogenerator (TENG) is a newly emerged technology for harvesting mechanical energy, which has the promise for various practical applications. Here, we introduce a new principle of TENG in which induced current is generated between two coplanar electrodes because of different dielectric fillers of distinct permittivities. The manipulation of permittivity of dielectric materials for TENG is first reported, demonstrating a novel route in designing high-performance TENGs. When repeatedly contacting with an object, a TENG having lateral dimensions of 21 mm × 10 mm can produce an open-circuit voltage of 58.5 V and a short-circuit current of 44.7 µA. The instantaneous output power density can reach up to 708 µW. Besides, the new design incorporates all electrodes into a single plane, greatly simplifying the structure, promoting robustness, and providing a viable solution for device miniaturization.

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Humidity sensors are commonly based on the resistance change of metal oxide semiconductors, which show high sensitivity in low humidity but low sensitivity in high humidity. In this work, we design a novel humidity sensor based on the airflow-induced triboelectric nanogenerator (ATNG) that can serve as a self-powered sensor to detect humidity (especially in high humidity) and airflow rate. The output current or voltage change is investigated under different humidity (20-100% relative humidity) at fixed airflow rate and different airflow rates (15-25 L/min) at a fixed humidity. The working principle of the ATNG-based sensor is illustrated. We find that both output current and voltage can serve as a variable for detecting humidity, while only the output current can serve as a variable for determining airflow rate. Our study demonstrates an innovative approach toward detection of humidity and airflow rate with advantages of self-power, multifunction, low cost, simple fabrication, and high sensitivity.

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A newly-designed triboelectric nanogenerator is demonstrated which is composed of a grating-segmented freestanding triboelectric layer and two groups of interdigitated electrodes with the same periodicity. The sliding motion of the grating units across the electrode fingers can be converted into multiple alternating currents through the external load due to the contact electrification and electrostatic induction. Working in non-contact mode, the device shows excellent stability and the total conversion efficiency can reach up to 85% at low operation frequency.