FLEXIBLE SURFACE ACOUSTIC WAVE (SAW) SENSORS FOR CRYOGENIC SENSING APPLICATION

Real-time monitoring of temperature and pressure, particularly in harsh environments such as extreme temperature and high electromagnetic radiation environments, has wide-ranging applications in the aerospace, civil infrastructure, and motor industries. Surface acoustic wave (SAW) technology has gained significant attention for harsh environment applications due to its ability to enable self-powered and wireless sensor devices that can operate in harsh environments. Our previous studies have demonstrated the effectiveness of 128 degrees YX-cut LiNbO3-based SAW sensors for cryogenic sensing applications with no degradation in sensor signals at cryogenic temperatures of 80K. However, the high value of the temperature coefficient of delay (TCD) presents a major challenge in developing wireless SAW pressure sensors, as even small changes in temperature can induce significant changes in the signal, which may be greater than that due to the pressure change of interest. Therefore, there is a need to improve the thermal stability and pressure sensitivity of the 128 degrees YX-cut LiNbO3-based SAW device. This paper reports on our simulation study of improving the thermal stability of the LiNbO3-based SAW sensor by applying an overlayer to compensate for the temperature effects. Additionally, we present our experimental study to develop a single crystalline thin-film-based SAW sensor, which has the potential to improve pressure sensitivity.