| The development of modern human civilization relies heavily on traditional fossil energy sources.However,with the rapid development of society,traditional fossil energy sources such as coal,oil,and natural gas have been in short supply.While these nonrenewable energy sources are being exploited on a large scale,they also pose a serious threat to the environment,causing widespread concern from all over the world.Besides,with the rapid development of the Internet of Things,a wide range of sensor devices such as temperature,light,sound,gas,and chemical sensors have profoundly affected all aspects of our lives.It is impractical that powering all these sensors by batteries,because of the enormous number and wide distribution of the devices,and difficulties to recycle wastes.Therefore,the development of new energy harvesting technologies is a common concern for countries around the world.Triboelectric nanogenerator(TENG)has the advantages of low cost,strong structural flexibility,rich material selection,etc.,and stands out from many energy harvesting technologies.The rapid development of TENG has attracted the attention of research organizations in various fields from energy to sensors since 2012 and has become one of the hottest research fields in the current.Notably,Triboelectric nanogenerator based on the freestanding triboelectric-layer mode is often used for harvesting complex ocean energy and self-power sensing due to its long service life,high energy conversion efficiency,and suitability for various scenarios.In this paper,our purpose is to efficiently harvest low-frequency ocean energy and achieve high-precision self-power mass sensing.TENGs base on freestanding triboelectric-layer mode have been designed for low-frequency ocean energy harvesting and self-power mass sensing.The main research work is as follows:(1)In this work,a teeterboard-like hybrid nanogenerator(named as THNG)has been fabricated for harvesting the widely distributed low-frequency ocean wave energy.The unique design includes a multi-layered TENG at one end of the teeterboard and an electromagnetic generator(EMG)at the other end.Benefiting from the novel design,the TENG unit can realize a full-packaged and light-weight structure that can be easily triggered by ocean waves with a low-frequency and it demonstrates desirable performance without environmental impact.Moreover,there is a separator between each pair of electrodes,which limits one tube only rolling over between two separators.This design has two advantages.One is to enable the motion of rolling tubes to fully cover the corresponding electrodes to generate electrical output,even when the hemisphere only swings at a small angle with a high-frequency incident wave.The other is to avoid the tubes gathering at one side of the chamber,in which case the gravity center of TENG will sharply shift and it will be very difficult for the device to swing back.At a frequency of0.8 Hz and an angle of 27 °,the maximum open-circuit voltage is ～ 780 V and the maximum short-circuit current is ～ 4 μA.The motion amplitude of the EMG unit can be easily adjusted by changing the fulcrum position between the TENG and EMG.Even in a slight wave state with aftershock vibrations,the EMG can still move with a reasonable amplitude to generate an ideal electrical output,which effectively improves the working efficiency of the EMG unit in a low-frequency environment.At a frequency of 0.8 Hz and an optimized fulcrum position,the short-circuit current of the EMG unit can be increased from ～ 3 m A to ～ 10 m A,and the open-circuit voltage can be increased from ～ 0.2 V to～ 2 V.What’s more,because of the innovative design,the THNG can automatically adjust the direction to match the incident wave and consequently capture wave energy from any directions.Also,under a simulated tide flow,the THNG can charge a 22 μF capacitor to3 V in 18 s,light more than 200 LEDs and drive a rain-drop senor directly to monitor the rainfall in the sea in real-time.This work provides a new and reliable idea for the efficient harvesting of ocean energy.(2)A one-dimensional underdamped motion mode Triboelectric nanogenerator has been designed for self-powered mass sensing(M-TENG).As we know,the laboratory electronic balance is of great accuracy,but it is subject to many restrictions in use.For example,to ensure measurement accuracy,it must be accurately leveled and calibrated.A slight improper operation can easily cause measurement errors and instrument damage.Not only that,other common tools for mass measuring,such as electronic scales,spring scales,weight scales,etc.,are based on Hooke’s law or the lever-balance principle of force,and cannot be used in completely weightless environments(such as space).Therefore,we designed a self-powered mass sensor(M-TENG)in this work.This sensor combines the kinematics of the vibrator and the characteristics of the electrical output to realize mass sensing,which is not only highly accurate but also suitable for a variety of environments.A typical M-TENG consists of two parts,vibrator,and bottom TENG.Generally,the vibrator damps vibrations under the actions of spring force,friction force,and air resistance.The TENG at the bottom transmits the motion signal of the vibrator.In this paper,we theoretically analyzed the vibrator motion characteristics in three different environments(air resistance only,friction only,and combination effect of air resistance and friction)in advance,from which we observed that the vibrator’s motion period can accurately reflect its mass when the measurement environment is fixed(that is when the air resistance is constant).To verify the above theory,we tested the effects of friction force,system tilt angle,and vibrator release position on the M-TENG quasi-period and the experimental results were consistent with the theoretical prediction.Moreover,benefiting from the working principle,M-TENG can work normally even at a completely weightless status,which is impossible for traditional quality measuring instruments.Further,the M-TENG took the period instead of amplitude of electrical output for sensing signal,therefore,the measurement accuracy will not be affected by environmental parameters such as temperature and humidity.In addition,M-TENG can not only achieve self-powered mass sensing but also can be used to measure vacuum rate and detect the uniformity of object surface. |
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