Research On Flexible Micro-nano Energy Harvesting Technology Based On Porous Structure

With the rapid development of Internet of things technology,a huge network composed of sensors and actuators has been integrated into every corner of the city.These devices provide technical support for physiological health detection,wearable electronic devices or artificial intelligence.The power required to drive these devices is not high,but because of its large number,it needs to have power supply equipment that can ensure mobility and sustainability as the basis.At present,many micro electronic devices are powered by batteries.However,the disadvantages of batteries that need to be replaced or charged frequently,and the environmental hazards caused by scrapping make micro-nano energy harvesting become a research hotspot in related fields.As a key technology in the field of micro-nano energy harvesting,nanogenerator can convert the energy such as vibration,heat or sound wave generated by small-scale physical changes into electric energy.Piezoelectric,triboelectric or pyroelectric Nanogenerator are its typical applications.Porous structure,or sponge structure,has a lot of advantages as a functional structure to realize the Nanogenerator,such as improving energy generation efficiency,high ductility and easy to be applied in life science.According to these above background,this dissertation mainly explored the fabrication process and measurement of piezoelectric Nanogenerator based on porous structure.The main work of this dissertation is summarized as follows:1.In this dissertation,the realization methods of porous polymer structure are firstly discussed,their advantages and disadvantages as well as the applicable environment are analyzed.Then the classification of materials which can achieve piezoelectric properties is introduced.Subsequently,a kind of porous polymer/nanocomposite was prepared with BaTiO₃ nanoparticles and MW-CNT as functional materials,PDMS as matrix materials and granulated sugar as sacrificial template by direct template method.The microstructure of this material is observed by SEM.2.In this dissertation,the principle of piezoelectric effect,the domain transition in the process of polarization,and the working principle of piezoelectric nanogenerator are discussed respectively.The influence of polarization electric field,temperature and time on the piezoelectric performance in the process of polarization and three kinds of commonly used polarization processes are analyzed.Then,a kind of polarization process was selected and optimized,through which a piezoelectric nanogenerator with micro-nano energy collection capacity is prepared.The influencing factors in the polarization process were summarized.The statistical data showed that for the porous structure composite with the thickness of 1 mm,the best polarization voltage was 12kV/mm,the polarization temperature was 90℃,and the polarization time was 40 min.Finally,the piezoelectric nanogenerator is tested by electrical signal output,positive and negative connection test,material characteristics test and output capacity test,which fully verified the piezoelectric output performance of this nanogenerator.3.In this paper,the output performance and characterization of piezoelectric nanogenerators are studied in two parts:the preparation process and the test conditions.Firstly,the thickness of the material,the doping concentration of BaTiO₃ nanoparticles and the doping of MW-CNT are studied.The results show that when the thickness is 2mm and the concentration of BaTiO₃ is 5 wt%,the Nanogenerator can achieve the highest energy collection efficiency with the doping of MW-CNT.Then,the influence of vibration frequency,vibration pressure and characterization error of test equipment on the test results of nanogenerator is explored.The results show that vibration frequency is not the fundamental factor affecting the output of nanogenerator,vibration pressure is linearly related to voltage output,and different test equipment will cause performance characterization error of nanogenerator.