Flexible LNO Thin Film SAWR Strain Sensor Based on Polyimide Substrate

Flexible single crystal 0°YX lithium niobite (LNO) thin film is fabricated on a polyimide substrate combining crystal-ion-slicing (CIS) technology and the benzocyclobutene (BCB) bonding method. By finite element method (FEM) simulation, a surface acoustic wave resonator (SAWR) with a ${Q}$ factor of 493 is demonstrated by increasing the thickness of the BCB layer. While applying compressively strain and tensile strain, the SAWR strain sensors show good performance with strain sensitivity of 587 Hz/ $\mu \varepsilon $ and a wider strain range from −2231 or $2241 \mu \varepsilon $ compared with our previous work in solidly mounted resonators (SMRs) and memristors. The repeatability testing while applying compressively strain and tensile strain is performed at two strain states of 0 and $- 1594\,\,\mu \varepsilon $ , and 0 and $1599 \mu \varepsilon $ , respectively. As changing the strain value, the resonance frequency shows great consistency and displays good repeatability and high stability, indicating that the flexible LNO SAWR strain sensor has potentially applicable in flexible electronics systems.