Preparation And Research On Characteristics Of Piezoelectric Self-driven Flexible Humidity Sensors

With the development of human science and technology,the shortage of energy and the environmental problems caused by the abuse of fossil energy have become increasingly apparent.The traditional sensors can only be driven by external power supply,which runs counter to people's demand for environmental protection in recent years.In this situation,people's research enthusiasm for self-driven sensors has been pushed to a new height.In this thesis,the application of piezoelectric nano generator(PENG)in the field of self-powered humidity sensor is studied.A layered piezoelectric self driving humidity sensor based on polyimide(PI)and a composite piezoelectric self driving humidity sensor based on polyetherimide(PEI)are proposed.The relevant sensitive materials are characterized and analyzed,and the performance of the sensor is tested and studied.The specific research contents are as follows:1.In this thesis,the composite fiber film of lead magnesium niobate lead titanate(PMN-PT)piezoelectric ceramics and polyvinylidene fluoride(PVDF)piezoelectric polymer was prepared by electrospinning,and the film was used as the energy supply layer of layered piezoelectric self driving flexible humidity sensor;Polyimide(PI)humidity sensitive film was prepared by spin coating method and thermal amination process,and the film was used as the humidity sensitive layer of layered piezoelectric self driving flexible humidity sensor.After combining the energy supply layer with the humidity sensitive layer and depositing the electrode,the layered piezoelectric self driving flexible humidity sensor sample is obtained.The effects of the thickness of the humidity sensitive layer and the porosity of the electrode on the performance of the sensor are studied,and its application in human physiological monitoring combined with insole is studied.The response time and recovery time measured at 77.2% porosity are 23 seconds and 31 seconds respectively.The maximum output voltage is 4.32 v when the PI thickness is 60?m,and the maximum sensitivity is 500% when the PI thickness is 20?m.2.In this thesis,the composite fiber film of PMN-PT piezoelectric ceramic and polyetherimide(PEI)polymer humidity sensitive material was prepared on the flexible aluminum substrate by electrospinning,and the electrode was installed on the surface of the film,so that a "sandwich" capacitive structure was formed between the electrode,the composite fiber film and the aluminum substrate to form a composite piezoelectric self driving humidity sensor.It is characterized by the composite of piezoelectric materials and humidity sensitive materials.The piezoelectric self driving function and the adsorption function of water molecules are completed by the single-layer structure of composite fiber film.In this thesis,the effects of electrospinning time,PMN-PT doping and electrode structure on the performance of the sensor are studied,and its application in the field of human physiological detection combined with mask is studied.When using copper mesh electrode,the measured response time and recovery time are20 seconds and 23 seconds respectively.The voltage output reaches the maximum value of about 8V when the mass fraction of PMN-PT is 7.5wt%.