Study On Passive Wireless Triboelectric Flexible Sensor And RF Transceiver System

Under the background of the information era and the Internet of things,the study on new wireless sensors is becoming increasingly important.The active wireless sensor requires an external power supply and complex active circuit,which limits its application in many scenarios,while the passive wireless sensor becomes the desired solution.Wireless surface acoustic wave（SAW）sensors stand as the perfect example of the passive wireless sensor,and it is a passive device integrating"wireless response function"and"sensing function".Making full use of the"wireless response function"of SAW devices to realize the passive wireless sensing of other conventional sensors will broaden the application of sensors.Triboelectric sensors are a kind of self-powered sensor,which show many advantages in flexible sensing.Hence,in this thesis,we propose the passive wireless sensing strategy of the triboelectric sensor by exploiting the acoustic surface wave resonator（SAWR）and its matching network as a transponder,which permits the scenarios of triboelectric sensor further broaden.The main work is provided as follows:（1）The basic principle and the structure of the SAWR are introduced.The method of extracting the parameters of the equivalent circuit for SAWR is analyzed,and the system transfer function of the SAWR is established based on the equivalent circuit.Utilizing the transfer function,the time-domain response of the SAWR to the typical signal is analyzed,and the response of the SAWR to the sinusoidal signal is simulated by MATLAB.（2）Based on the analysis of the basic principle of typical triboelectric sensors and the structure of common triboelectric sensors,a flexible triboelectric pressure sensor with a hollow cylindrical shape with a concave-convex profile was designed and fabricated.The concave-convex profile and the elasticity of the friction layer allow the friction layer to separate effectively.The concave-convex and rough surface of the friction layer increases the actual contact area.The charge transfer mechanism of the triboelectric sensor with the load is analyzed.The parameters of the designed sensor were tested,which shows that the sensor exhibits good linearity,its sensitivity is 2.63V N^-1,and it maintains a stable output under 15000 repeated pressure tests.（3）The matching process of the SAWR used to wireless sensing is studied.The equivalent circuit of the SAWR is converted into an equivalent RLC series circuit or an equivalent GLC parallel circuit.The principles of the low-mismatch T-type and the Pi-type matching networks are analyzed,and board-level parasitic parameters are reasonably evaluated using ADS simulation tools to complete matching from the SAWR to the antenna.The approximate expression of the resonance frequency of the SAWR changing with the parameters of the matching network is derived.The sensitivity and linearity of the wireless sensors with these two types of matching networks were compared.（4）The principle of modulation of the triboelectric output voltage to SAWR’s response signal is investigated.The approximate mathematical expression between the response signal frequency and the voltage is derived.Further,utilizing the mathematical relationship between the input and the output of the triboelectric sensor,the relational expression between the input pressure and the output frequency of the wireless sensor is obtained.The voltage（or pressure）-resonance frequency curve and the voltage（or pressure）-amplitude curve are measured through experiments.Theoretical analysis and experimental tests show that the wireless sensor using the T-type network has higher sensitivity than the Pi-type network.（5）The RF transceiver system is designed and manufactured,and it includes the interrogator RF front end,data acquisition module,USB high-speed transmission channel,upper computer,etc.Combined with the sensor designed,the passive wireless triboelectric sensing system is constructed.Three demonstrations are designed to preliminarily show the application prospects of the passive wireless triboelectric sensor designed in this thesis.