Research Of MEMS Integrated Formaldehyde Sensor And Performance Testing

Formaldehyde is one of main pollutants of indoor air, which releases byhome building materials and furniture and has great harm to human health. Thecurrent spectrophotometry and chromatography are unable to meet therequirements of on-site rapid detection of formaldehyde, and complex operation,a large volume of testing equipment, expensive, and therefore, it is verynecessary to develop a portable formaldehyde detector.Considering the shortage of traditional detection method and the demand ofdomestic market, this issue analysis the character of metal oxide semiconductorsensor and the mechanism of gas-sensing in combination with nanotechnology, asemiconductor microstructure nano-zinc oxide MEMS formaldehyde sensorbased on AIN was designed. The sensor had high testing accuracy, low cost, anda field-based test. The main work of design are follows：The structure of MEMS sensor was designed， according to the heatanalysis of finite element analysis software, the optimization was achieved; Thefinite element method was used for analysis of heat stress. The simulation andanalysis of heat stress was used for sensor structure under the work conditions toprove its feasibility.Zinc Oxide (ZnO) anti-bacterial materials were prepared by sol-gel method,mixing a certain proportion of H2PtCl6、La2O3in ZnO to improve its gassensitive properties. The results of scanning electron microscope and TG/DTAtechnology analysis showed that the size of ZnO powder was nanometer scalewith good dispersion.A detection circuit of MEMS integrated formaldehyde sensor was designed.Hardware circuit was divided into three modules: heating circuit with sensitivegas material, sensitive materials and environmental temperature measurementcircuit, the concentration of gas sensing signal conditioning circuit. The research of software section focused on temperature-programmed system of the chip,which controlled the real-time temperature of table, and greatly improved thestability and gas sensitivity of sensor.MEMS integrated formaldehyde sensor was prepared and tested forperformance. The results showed that: optimum voltage was3.9V, response timewas6s, recovery time was15s, detection range was5~155ppm, the optimumoperating temperature was300~320℃, the sensor had a good selectivity onalcohol, gasoline, carbon monoxide and other gases. But the resolution andconsistency should be improved greatly. Test data was calibration fit by the leastsquares method, which reduced calibration points while ensuring accuracy andsimplified the operation of calibration online.