Publications

We report a systematic study about the anisotropic third-order optical nonlinearity of a single ZnO micro/nanowire by using the Z-scan method with a femtosecond laser. The two-photon absorption coefficient and nonlinear refraction index, which are measured as a function of polarization angle and sample orientation angle, exhibit oscillation curves with a period of π/2, indicating a highly polarized optical nonlinearity of the ZnO micro/nanowire. Further studies show that the polarized optical nonlinearity of the ZnO micro/nanowire is highly size-dependent. The results indicate that ZnO nanowire has great potential in applications of nanolasers, all-optical switching and polarization-sensitive photodetectors.

Moving to mercury: The first triboelectric effect-based sensor for the detection of Hg2+ ions by using Au nanoparticles (see picture; red) as electrical performance enhancer and recognition element has been successfully demonstrated. This self-powered and stand-alone triboelectric nanosensor has the advantages of simplicity, low cost, high selectivity, and sensitivity. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

We present triboelectrification based, flexible, reusable, and skin-friendly dry biopotential electrode arrays as motion sensors for tracking muscle motion and human–machine interfacing (HMI). The independently addressable, self-powered sensor arrays have been utilized to record the electric output signals as a mapping figure to accurately identify the degrees of freedom as well as directions and magnitude of muscle motions. A fast Fourier transform (FFT) technique was employed to analyse the frequency spectra of the obtained electric signals and thus to determine the motion angular velocities. Moreover, the motion sensor arrays produced a short-circuit current density up to 10.71 mA/m2, and an open-circuit voltage as high as 42.6 V with a remarkable signal-to-noise ratio up to 1000, which enables the devices as sensors to accurately record and transform the motions of the human joints, such as elbow, knee, heel, and even fingers, and thus renders it a superior and unique invention in the field of HMI.

We report a self-powered, single-electrode-based triboelectric sensor (SE-TES) array for detecting object motion inside of a plastic tube. This innovative, cost-effective, simple-designed SE-TES consists of thin-film-based ring-shaped Cu electrodes and a polytetrafluoroethylene (PTFE) tube. On the basis of the coupling effect between triboelectrification and electrostatic induction, the sensor generates electric output signals in response to mechanical motion of an object (such as a ball) passing through the electrodes. An array of Cu electrodes linearly aligned along the tube enables the detection of location and speed of the moving steel ball inside. The signal-to-noise ratio of this fabricated device reached 5.3 × 103. Furthermore, we demonstrated real-time monitoring and mapping of the motion characteristics of the steel ball inside the tube by using a seven-unit array of electrode channels arranged along the tube. Triggered by the output current signal, LED bulbs were utilized as real-time indicators of the position of a rolling ball. In addition, the SE-TES also shows the capability of detecting blockage in a water pipe. This work demonstrates potentially widespread applications of the triboelectric sensor in a self-powered tracking system, blockage detection, flow control, and logistics monitoring.

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.

'Plasma-Enhanced Chemical Vapor Deposition (PECVD)' published in 'Encyclopedia of Nanotechnology'

The physical filtration mechanism of a traditional face mask has a low removal efficiency of ultrafine particulates in the size range of 10–1000 nm, which are badly harmful to human health. Herein, a novel self-powered electrostatic adsorption face mask (SEA-FM) based on the poly(vinylidene fluoride) electrospun nanofiber film (PVDF-ESNF) and a triboelectric nanogenerator (TENG) driven by respiration (R-TENG) is developed. The ultrafine particulates are electrostatically adsorbed by the PVDF-ESNF, and the R-TENG can continually provide electrostatic charges in this adsorption process by respiration. On the basis of the R-TENG, the SEA-FM shows that the removal efficiency of coarse and fine particulates is higher than 99.2 wt % and the removal efficiency of ultrafine particulates is still as high as 86.9 wt % after continually wearing for 240 min and a 30-day interval. This work has proposed as a new method of wearable air filtration and may have great prospects in human health, self-powered electronics, and wearable devices.

Abstract Acceleration sensors have wide applications in earthquake warning, human motion recognition, vehicle restraint system, etc. However, the existing commercial acceleration sensors have some limitations on needing an external power supply, high fabrication cost, and small signal when self‐powered. Here a grating‐structured freestanding triboelectric nanogenerator (GF‐TENG) capable of sensing displacements, velocities, and accelerations in real‐time is presented with self‐powered, low cost, and sufficiently large signal. The slider with grating‐structured electrodes of GF‐TENG sliding over the stator with another grating‐structured electrode generates the periodic open‐circuit voltage due to electrostatic induction. By recognizing the shape of open‐circuit voltage, it could sense the acceleration in real time even at scales down to hundred microns through systematic optimization of simulations and experiments. Furthermore, the acceleration sensing range could be expanded to the desired ranges, such as 5.0 to 45.0 m s –2 , by assembling springs and GF‐TENG into a grating‐structured TENG‐based acceleration sensor (GTAS). Moreover, GTAS is demonstrated to sense the vehicle motion and be a part of the vehicle restraint system on a model car. This work reports a new self‐powered acceleration sensor with sufficiently large outputs for real‐time motion sensing and collision detection, which could be further applicated for robotics and human motion recognition.

In situ conversion of mechanical energy into electricity is a feasible solution to satisfy the increasing power demand of the Internet of Things (IoTs). A triboelectric nanogenerator (TENG) is considered as a potential solution via building self-powered systems. Based on the triboelectrification effect and electrostatic induction, a conventional TENG with pulsed AC output characteristics always needs rectification and energy storage units to obtain a constant DC output to drive electronic devices. Here, we report a next-generation TENG, which realizes constant current (crest factor, ~1) output by coupling the triboelectrification effect and electrostatic breakdown. Meanwhile, a triboelectric charge density of 430 mC m-2 is attained, which is much higher than that of a conventional TENG limited by electrostatic breakdown. The novel DC-TENG is demonstrated to power electronics directly. Our findings not only promote the miniaturization of self-powered systems used in IoTs but also provide a paradigm-shifting technique to harvest mechanical energy.