Xiangyu Chen

Ultrastretchable, transparent triboelectric nanogenerator as electronic skin for biomechanical energy harvesting and tactile sensing

Stretchable, transparent nanogenerator enabled by ionic hydrogel converts motion energy into electricity and senses touch pressure. Rapid advancements in stretchable and multifunctional electronics impose the challenge on corresponding power devices that they should have comparable stretchability and functionality. We report a soft skin-like triboelectric nanogenerator (STENG) that enables both biomechanical energy harvesting and tactile sensing by hybridizing elastomer and ionic hydrogel as the electrification layer and electrode, respectively. For the first time, ultrahigh stretchability (uniaxial strain, 1160%) and transparency (average transmittance, 96.2% for visible light) are achieved simultaneously for an energy-harvesting device. The soft TENG is capable of outputting alternative electricity with an instantaneous peak power density of 35 mW m−2 and driving wearable electronics (for example, an electronic watch) with energy converted from human motions, whereas the STENG is pressure-sensitive, enabling its application as artificial electronic skin for touch/pressure perception. Our work provides new opportunities for multifunctional power sources and potential applications in soft/wearable electronics.

Structural Optimization of Triboelectric Nanogenerator for Harvesting Water Wave Energy.

Ocean waves are one of the most abundant energy sources on earth, but harvesting such energy is rather challenging due to various limitations of current technologies. Recently, networks formed by triboelectric nanogenerator (TENG) have been proposed as a promising technology for harvesting water wave energy. In this work, a basic unit for the TENG network was studied and optimized, which has a box structure composed of walls made of TENG composed of a wavy-structured Cu-Kapton-Cu film and two FEP thin films, with a metal ball enclosed inside. By combination of the theoretical calculations and experimental studies, the output performances of the TENG unit were investigated for various structural parameters, such as the size, mass, or number of the metal balls. From the viewpoint of theory, the output characteristics of TENG during its collision with the ball were numerically calculated by the finite element method and interpolation method, and there exists an optimum ball size or mass to reach maximized output power and electric energy. Moreover, the theoretical results were well verified by the experimental tests. The present work could provide guidance for structural optimization of wavy-structured TENGs for effectively harvesting water wave energy toward the dream of large-scale blue energy.

Triboelectric Nanogenerator as a Self-Powered Communication Unit for Processing and Transmitting Information

In this paper, we demonstrate an application of a triboelectric nanogenerator (TENG) as a self-powered communication unit. An elaborately designed TENG is used to translate a series of environmental triggering signals into binary digital signals and drives an electronic-optical device to transmit binary digital data in real-time without an external power supply. The elaborately designed TENG is built in a membrane structure that can effectively drive the electronic-optical device in a bandwidth from 1.30 to 1.65 kHz. Two typical communication modes (amplitude-shift keying and frequency-shift keying) are realized through the resonant response of TENG to different frequencies, and two digital signals, i.e., 1001 and 0110, are successfully transmitted and received through this system, respectively. Hence, in this study, a simple but efficient method for directly transmitting ambient vibration to the receiver as a digital signal is established using an elaborately designed TENG and an optical communication technique. This type of the communication system, as well as the implementation method presented, exhibits great potential for applications in the smart city, smart home, password authentication, and so on.

Theoretical study on rotary-sliding disk triboelectric nanogenerators in contact and non-contact modes

The triboelectric nanogenerator (TENG) has emerged as a new and effective mechanical energy harvesting technology. In this work, a theoretical model for a rotary-sliding disk TENG with grating structure was constructed, including the dielectric-to-dielectric and conductor-to-dielectric cases. The finite element method (FEM) was utilized to characterize the fundamental physics of the rotarysliding disk TENG working in both contact and non-contact modes. The basic properties of disk TENG were found to be controlled by the structural parameters such as tribo-surface spacing, grating number, and geometric size. From the FEM calculations, an approximate V–Q–α relationship was built through the interpolation method, and then the TENG dynamic output characteristics with arbitrary load resistance were numerically calculated. Finally, the dependencies of output power and matched resistance on the structural parameters and rotation rate were revealed. The present work provides an in-depth understanding of the working principle of the rotary-sliding disk TENG and serves as important guidance for optimizing TENG output performance in specific applications.

Self-Powered Microfluidic Transport System Based on Triboelectric Nanogenerator and Electrowetting Technique

Electrowetting technique is an actuation method for manipulating position and velocity of fluids in the microchannels. By combining electrowetting technique and a freestanding mode triboelectric nanogenerator (TENG), we have designed a self-powered microfluidic transport system. In this system, a mini vehicle is fabricated by using four droplets to carry a pallet (6 mm × 8 mm), and it can transport some tiny object on the track electrodes under the drive of TENG. The motion of TENG can provide both driving power and control signal for the mini vehicle. The maximum load for this mini vehicle is 500 mg, and its highest controllable velocity can reach 1 m/s. Freestanding TENG has shown excellent capability to manipulate microfluid. Under the drive of TENG, the minimum volume of the droplet can reach 70-80 nL, while the tiny droplet can freely move on both horizontal and vertical planes. Finally, another strategy for delivering nanoparticles to the designated position has also been demonstrated. This proposed self-powered transport technique may have great applications in the field of microsolid/liquid manipulators, drug delivery systems, microrobotics, and human-machine interactions.

Triboelectric sensor as self-powered signal reader for scanning probe surface topography imaging

We report a self-powered signal reading mechanism for imaging surface topography using a triboelectric sensor (TES) without supplying an external power or light source. A membrane-structured triboelectric nanogenerator (TENG) is designed at the root of a whisker (probe); the deflection of the whisker causes the two contacting surfaces of the TENG to give an electric output current/voltage that responds to the bending degree of the whisker when it scans over a rough surface. A series of studies were carried out to characterize the performance of the TES, such as high sensitivity of 0.45 V mm(-1), favorable repeating of standard deviation 8 mV, high Z-direction resolution of 18 μm, as well as lateral resolution of 250 μm by using a probe of size 11 mm in the length and 120 μm in radius. It not only can recognize the surface feature and size but also can perform a surface topography imaging in scanning mode. This work shows the potential of a TES as a self-powered tactile sensor for applications at relatively low spatial resolution.

Field emission device driven by self-powered contact-electrification: Simulation and experimental analysis

A self-powered field emission device (FED) driven by a single-electrode tribo-electric nanogenerator (TENG) is demonstrated. The mechanical motion works as both a power supply to drive the FED and a control unit to regulate the amount of emitted electrons. By using the Fowler-Nordheim equation and Kirchhoff laws, a theoretical model of this self-powered FED is proposed, and accordingly the real-time output characteristics of the device are systematically investigated. It is found that the motion distance of the TENG controls switch-on of the FED and determines the charge amount for emission, while the motion velocity regulates the amplitude of emission current. The minimum contact area for the TENG to generate field emission is about 9u2009cm2, which can be improved by optimizing FED structure and the tribo-materials of TENG. The demonstrated concept of this self-powered FED as well as the proposed physical analysis can serve as guidance for further applications of FED in such fields of self-powered electroni...

Motion behavior of water droplets driven by triboelectric nanogenerator

By integrating a triboelectric nanogenerator (TENG) and a simple circuit board, the motion of water droplets can be controlled by the output of the TENG, which demonstrates a self-powered microfluidic system toward various practical applications in the fields of microfluidic system and soft robotics. This paper describes a method to construct a physical model for this self-powered system on the basis of electrostatic induction theory. The model can precisely simulate the detailed motion behavior of the droplet under driving of TENG, and it can also reveal the influences of surface hydrophobicity on the motion of the droplet, which can help us to better understand the key parameters that decide the performance of the system. The experimental observation of the dynamic performance of the droplet has also been done with a high speed camera system. A comparison between simulation results and real measurements confirms that the proposed model can predict the velocity and position of the water droplet driven by high voltage source as well as TENG. Hence, the proposed model in this work could serve as a guidance for optimizing the self-powered systems in future studies.By integrating a triboelectric nanogenerator (TENG) and a simple circuit board, the motion of water droplets can be controlled by the output of the TENG, which demonstrates a self-powered microfluidic system toward various practical applications in the fields of microfluidic system and soft robotics. This paper describes a method to construct a physical model for this self-powered system on the basis of electrostatic induction theory. The model can precisely simulate the detailed motion behavior of the droplet under driving of TENG, and it can also reveal the influences of surface hydrophobicity on the motion of the droplet, which can help us to better understand the key parameters that decide the performance of the system. The experimental observation of the dynamic performance of the droplet has also been done with a high speed camera system. A comparison between simulation results and real measurements confirms that the proposed model can predict the velocity and position of the water droplet driven by...

Capsule Triboelectric Nanogenerators: Toward Optional 3D Integration for High Output and Efficient Energy Harvesting from Broadband-Amplitude Vibrations

The technology of triboelectric nanogenerators (TENGs) has made great progress as a promising approach to generating electricity from ambient vibration energy. However, finding a way to generate enough electrical output efficiently from vibrations with a broadband of amplitudes is crucial when the relatively low current output of existing TENGs and the existence of natural vibrations with diverse amplitudes are considered. In this work, a freestanding and lightweight triboelectric nanogenerator with a capsule structure (namely, a capsule TENG) is demonstrated with an aim toward optional 3D integration and the efficient harvesting of energy from vibrations with a broadband of amplitudes. The capsule TENGs can be easily integrated to form 1D, 2D, and 3D structures to realize high electrical output. Under ideal conditions, the total output power of an integrated capsule-TENG pack can be approximately estimated as p × n2, where p is the peak output power per capsule TENG and n is the number of capsule TENGs. When capsule TENGs with hybrid structures, such as different lengths of the capsule tube and different numbers of paired electrodes, are assembled, energy can be more efficiently harvested from vibrations with a broadband of amplitudes. A total of three parameters (the active area-to-volume ratio, the power-to-volume ratio, and the power-to-weight ratio), which are important parameters for 3D-integrated TENGs, are proposed. The results of this research show that capsule TENGs are versatile devices that can potentially be used for the efficient harvesting of ambient vibration energy.

Giant Voltage Enhancement via Triboelectric Charge Supplement Channel for Self-Powered Electroadhesion

Electroadhesion generates an adhesion force using an externally applied power source, which has versatile applications in robotics and material handling. In this study, a self-powered electroadhesion system using enhanced triboelectric nanogenerators (TENGs) to supply power for electroadhesion is presented. By introducing a triboelectric charge supplement channel, the open circuit voltage of the TENG can be significantly boosted by over 10 times, from ∼230 V to more than 3300 V for a single TENG unit, providing sufficiently high voltage for an electroadhesive patch to generate enough adhesion for practical use. The charge supplement channel takes effect through a replenishing mechanism for dissipated charges, maintaining an optimal charge distribution throughout TENG electrodes, which enables the highest open circuit voltage under given surface charge density and device configuration. The fabricated self-powered electroadhesion system shows the ability to manipulate objects of various materials via easy and straightforward operations, demonstrating a great potential for applications in material handling and robotics. Moreover, the voltage enhancement mechanism by the charge supplement channel could be extended to TENGs of other modes, which can provide reliable power sources for various applications that require a high voltage.