Research On Self-actuated Sensing Based On Liquid-solid Nanogenerator

Liquid-solid triboelectric nanogenerator（L-S TENG）is a self-powered sensor that can generate charge through the friction between liquid droplets and solid surfaces,realizing autonomous energy harvesting and signal detection.Due to its strong self-driving ability,wide range of applications,and low cost,it has been widely used in fields such as smart Io T,wearable devices,medical equipment,and environmental monitoring.However,the working mechanism of L-S TENG is still unclear,and it is difficult to accurately regulate its performance.In addition,during the working process,the output signal of L-S TENG is unstable and the energy conversion efficiency is not high,which still faces significant challenges in practical applications.Therefore,this thesis mainly conducts in-depth research on the working mechanism and performance optimization of L-S TENG,with the main research contents as follows:1.Research on L-S TENG mainly focuses on the liquid-solid contact interface,while the impact of the friction layer（polarization layer）and the electrode layer interface,as well as the interaction between the"liquid-solid interface"and the"polarization layer-electrode layer"can be easily ignored.We propose a mechanism of the synergistic effect of L-S TENG dual interfaces,and through electrochemical impedance experiments and COMSOL simulation,we prove the existence of the liquid-solid interface and the"polarization layer-electrode layer"interface.We propose a response voltage formula under the mechanism of synergistic effect of dual interfaces:U=εc v.This mechanism can well explain the influence of the droplet concentration,volume,type,speed,ion intensity,and dual interface resistance on the response voltage.Under the same experimental conditions,the relationship between the response voltage of L-S TENG and the droplet velocity is perfectly consistent with U=,which verifies the rationality of the mechanism of synergistic effect of dual interfaces.The proposal of the mechanism of synergistic effect of dual interfaces provides a new idea for precise regulation of the performance of liquid-solid frictional nano-generator.2.The main reason for the unstable output performance of the nano-generator is the contact and reaction between the droplet and it.Therefore,we propose a liquid-solid noncontact nanogenerator strategy（L-S NCNG）,which can effectively avoid the contact between the droplet and the polarization layer and neutralize its charge.Experiments show that L-S NCNG maintains a stable output signal throughout 1200s through the synergistic effect between the water molecule layer-polarization layer-electrode layer.In contrast,the output decay of contact-type L-S TENG is severe.L-S NCNG also has good recognition effects on information such as the direction,speed,frequency,type,and concentration of droplet movement,which is expected to be used for intelligent management and control in the infusion process.In addition,L-S NCNG can also generate electricity under droplet stimulation,which can be used to promote plant growth.The growth situation of plants stimulated by electricity（with an area of 1.91cm₂）is significantly better than that of the control group（with a leaf area of only 1.25cm₂）.L-S NCNG provides a practical new working mode for liquid-solid nano-generator.3.The fundamental reason for the low energy conversion efficiency of nanogenerators is the easy trapping and detrapping of shallow-trap charges in the piezoelectric material.After doping PMMA with appropriate narrow-bandgap Ti O₂,it can capture and store more stable deep-trap charges.The surface potential of Ti O₂-PMMA is as high as 3000V,significantly higher than that of unmodified PMMA（surface potential～2000V）,indicating that Ti O₂-PMMA can more effectively capture charges.Even after 1800 hours,Ti O₂-PMMA can still maintain a high charge density with a surface potential of～1000V,while unmodified PMMA has a surface potential of only～500V.The thermal-stimulated discharge current peak of Ti O₂-PMMA shifts noticeably from 90.0℃to 103.5℃,indicating that charges are stored in deeper traps.The maximum output of unmodified PMMA is only 40 m V,while Ti O₂-PMMA maintains a stable 80 m V voltage output in long-term cycling experiments,with energy conversion efficiency twice that of unmodified PMMA.Therefore,the bandgap adjustment strategy can effectively solve the problem of low energy conversion efficiency of L-S TENG.