Research On Output Performance And Stability Optimization Of Water Droplet Triboelectric Nanogenerator

In 2012,Academician Wang Zhonglin and his team first invented and reported the triboelectric nanogenerator(TENG).As a new energy harvesting technology,TENG can obtain mechanical energy in the surrounding environment and convert it directly into electrical energy.The power source of TENG can be not only large energy sources such as water power,wind power,and waves,but also random energy sources in the surrounding environment,such as falling raindrops,human movement,finger touch,mechanical roar,and wheel rotation.Compared with traditional electromagnetic induction generators,TENG has the advantages of simple structure,low fabrication cost,light weight,and high power conversion efficiency at low frequencies.At present,researchers have developed TENGs with different working modes,such as vertical contact-separation mode,single-electrode mode,horizontal sliding mode,and independent friction layer mode.Since the development of TENG,significant progress has been made in the fields of energy harvesting,self-driven sensing,and blue energy.In 2014,the team of Academician Wang Zhonglin first reported the water droplet TENG,which can harvest energy from falling water droplets and convert it into electricity.Since then,the phenomenon of solidliquid contact electrification has received extensive attention.Most of the water droplet TENGs reported so far adopt a hydrophobic structure.Compared with the traditional friction layer,the hydrophobic friction layer is improved several times in terms of open circuit voltage,short circuit current,and transferred charge amount.This is because the viscous force received by the water droplets on the surface of the hydrophobic structure is small.The separation speed of the water droplets and the friction layer is fast.The electrical output performance of the water droplet TENG is higher.A 2020 work by the team of researcher Chen Xiangyu showed that the amount of charge transferred between water droplets and the friction layer is positively related to their contact area.The use of superhydrophobic friction layers increases the speed of water droplet movement,but also brings about the problem of small contact area.However,the water droplets move slowly on the surface of the friction layer of the hydrophilic structure.Thus,the output performance of the water droplet TENG is limited.Therefore,how to solve the contradiction between the contact area of the water droplet and the TENG and the movement speed of the water droplet is the key to improve the output performance of the water droplet TENG.In the third chapter,the process of water droplet TENG using electrostatic induction to generate electricity is analyzed.The water droplets are separated from the friction layer of the device for a long time.The water will neutralize/carry away part of the charge on the friction layer.The surface charge density of the friction layer is attenuated,resulting in a smaller decrease in the electrical output performance of the TENG and poorer stability.The solution is to introduce a friction layer with a certain surface structure on the surface of the friction layer.Reduce the direct contact area of water droplets with the friction layer.Improve the output stability of triboelectric nanogenerators.The first tuning method is to design dielectric tribolayers with periodic micro-nano structures.The direct contact area between the water droplet and the friction layer is reduced,and the spatial structure of the solid-liquid contact interface is increased.The second modulation method is to introduce a layer of polymer brushes on the surface of the device.The space structure of the solid-liquid contact interface is increased,and the direct contact between the water droplets and the charges of the tribolayer is blocked.The stability of the solid-liquid TENG work is ensured by these two control methods.In the third chapter,through the analysis of the working mechanism of water droplet TENG,in the process of using electrostatic induction to generate electricity,it is concluded that the long-term contact and separation of water droplets with the friction layer,the water will neutralize/take away the part in friction The charge on the layer causes the surface charge density of the tribolayer to attenuate,resulting in a smaller decrease in the electrical output performance and poorer stability of the TENG.The solution is to introduce a friction layer with a certain surface structure on the friction layer to reduce the direct contact area between the water droplets and the friction layer.The first control method is to design a dielectric friction layer with periodic micro-nano structure to reduce the direct contact area between water droplets and the friction layer and increase the spatial structure of the solid-liquid contact interface.The second tuning method is to introduce a layer of polymer brushes on the surface of the device.The space structure of the solid-liquid contact interface is increased,and the direct contact between the water droplets and the charges of the tribolayer is blocked.The stability of the solid-liquid TENG work is ensured by these two control methods.In this paper,by introducing the oil gel as the friction layer,the contradiction between the contact area and the moving speed of the water droplet and the device is resolved.The electrical output was tripled from previous research.In addition,the device was regulated by two methods.The stability of solid-liquid TENG work is improved.These two works provide novel research ideas and solid technical support for the future work of water droplet TENG.