A Miniaturized Integrated SAW Sensing System for Relative Humidity Based on Graphene Oxide Film

Humidity detection has significant and extensive applications in various fields. Herein, a miniaturized integrated relative humidity (RH) sensing system from surface acoustic wave (SAW) sensor to circuits and software is described. Delay-line SAW devices were designed and fabricated to be used as sensor and reference device. Graphene oxide (GO) was deposited on the surface of SAW sensor between interdigitated transducers (IDTs) as ultra-thin and wrinkled sensitive film by the method of drop-cast. The well-matched circuits and software with excellent stability and accuracy were developed to form a miniaturized integrated relative humidity sensing system with SAW sensor. A linear variation of the frequency shift is obtained in an extremely wide detection range from 0 to 97.3 %RH. Besides, the system exhibits a high sensitivity of 3.33 kHz/%RH, rapid response time of 80 s and recovery time of 72 s, good dynamic response and excellent repeatability. These results demonstrate that the SAW sensing system not only realizes humidity detection at system level, but also has excellent performance, which shows great feasibility and tremendous potential for relative humidity measurement applications.