Research And Application Of Triboelectric Nanogenerators With Constant Capacitance

Contact electrification is a common phenomenon in daily life.Triboelectric nanogenerators(TENGs)are invented based on the phenomena of contact electrification and electrostatic induction to convert the superfluous mechanical energy in the ambient environment into electricity,which is a green and sustainable new energy collection technology to power portable and wearable devices.However,the large and time-dependent internal impedance greatly hinders the applications of TENG.When the mechanical motion frequency of the TENG matches the circuit characteristic frequency,the output power reaches its maximum value.However,the inherent capacitance of most TENGs is not constant,which makes it difficult to match the mechanical motion frequency with the circuit characteristic frequency,resulting in low output power.Therefore,to solve this problem,this paper proposed a TENG structure with constant inherent capacitance,which allows for constant internal impedance of the TENG.The advantages in applications of output power,self-powered sensors and power management circuits are also demonstrated.The results are as follows:Firstly,a theoretical model of TENG with constant capacitance is established based on fundamental physics and the working principle and energy-converting mechanism is analyzed in detail.The expressions of the key output parameters of the TENGs with the constant capacitance model and the conditions for achieving the maximum output power are given.The figures of merits and optimization strategy are proposed,which provides guidance for optimization of material selection and device structure design.Secondly,we used PVC and PET as friction materials and copper flakes as electrode materials to fabricate TENGs with constant inherent capacitances and studied the influence of different device structure parameters on the output performance.At optimal conditions,the open-circuit voltage reached 520 V,while the short-circuit current reached 7μA and the transferred charge reached as high as 3.1μC/cycle.A maximum instantaneous power reached as high as 33.3 m W/m~2,which is better than most of the results from literature.Finally,by comparing the synergetic usage of the TENG with three common power management circuits,we find out the power management circuit which has a optimal match with the TENG with constant capacitance.In order to demonstrate the application advantages of the TENG with a constant capacitance,an anemometer based on it is fabricated.By extracting the slope of output waveform of the TENG with a constant capacitance,we can obtain the temporary wind speed,so as to measure the wind speed and design a complete system to display it in real time.