Optimization Design Of Surface Acoustic Wave Gas Sensor And Preparation Of Sensitive Membrane

At present,people pay special attention to the detection of harmful or dangerous gases.While developing new gas sensors,they are also constantly exploring new sensing principles.Among them,surface acoustic wave(SAW)gas sensors have attracted attention because of their high sensitivity and strong anti-interference ability.In this paper,the composition,principle,manufacturing process and characteristics of resonant and delayed linear SAW gas sensors are comprehensively compared and studied.According to the floating electrode unidirectional transducer(FEUDT)structure,the SAW gas sensor insertion loss can be reduced.A SAW gas sensor with FEUDT structure is designed.The main components of the sensor: interdigital transducer,reflective grating and sensitive membrane are studied.From the point of view of the selectivity and adsorption efficiency of gas sensing materials,the linear solvation energy relationship(LSER)equation was used to determine the main material of polyethyleneimine(PEI)as a sensitive film for SAW gas sensors.Nitrotoluene(TNT)gas.Then,using the finite element method,the structural characteristics of the FEUDT are studied in detail from the aspects of modal analysis,admittance analysis,energy flow transmission characteristics and insertion loss.The results show that the FEUDT structure is unidirectional and can effectively stimulate the positive SAW.The FEUDT structure was applied to the delay line type and resonance type SAW gas sensor,and a two-dimensional model of the SAW gas sensor with FEUDT structure was constructed.By comparing the insertion loss and sensitivity of the delay line type and resonance type SAW sensor having the FEUDT structure,it is explained that the delay line type gas sensor has higher sensitivity and smaller insertion loss than the resonance type gas sensor.Finally,the advantages and disadvantages of several common membrane-forming methods were analyzed.The sensitive membranes were prepared by gas spraying method.The effects of spraying times and spraying distance on the film-forming quality of sensitive membranes were studied.