Integrated micro humidity sensor with polypyrrole and readout circuit

• Main Authors: De-Hao Lu, 盧德豪
• Other Authors: Ching-Liang Dai
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/47107253839884560848

碩士 === 國立中興大學 === 機械工程學系所 === 97 === This study investigates a micro humidity sensor integrated with readout circuit, which is fabricated by the commercial CMOS (complementary metal oxide semiconductor) process. The sensing film of the humidity sensor is polypyrrole that is synthesized by oxidative polymerization method. The electrodes consist of improved interdigital structures, and the polypyrrole is coated on the interdigital electrodes. The sensing principle of the sensor is based on the dielectric constant change when the sensing film absorbs or desorbs vapor. The humidity sensor includes a ring oscillator circuit, which converts the capacitance variation into the resonant frequency output. The experimental results show that the optimal operating temperature for the sensor is at room temperature. The capacitance increases from 17.54pF to 35.06pF as the humidity changes from 25%RH to 85%RH at 25℃. The resonant frequency of the sensor with readout circuit varies from 38.49MHz to 32.19MHz under the humidity range of 25%-85%RH at 25℃. The average response and recovery time are 36s and 191s, respectively.