Bendable transparent ZnO thin film surface acoustic wave strain sensors on ultra-thin flexible glass substrates
Flexible and transparent (FT) ZnO thin film based surface acoustic wave (SAW) devices using indium tin oxide (ITO) electrodes were fabricated on ultrathin flexible glass substrates. The influence of the annealing process and ITO thickness on the optical properties and acoustic wave power transmission properties of the devices was investigated. The performance of the devices improved significantly when the annealing temperature was raised up to 300 °C. The flexible glass based SAW devices exhibited similar power transmission performance, but have a better optical transmittance than those on rigid glass. These FT strain sensors worked well under various applied strains up to ±3000 με with fast response time, and showed excellent linearity of resonant frequency with the change of strain with a sensitivity of ∼34 Hz με−1. The strain sensors demonstrated excellent stability and reliability under cyclic bending. The results demonstrated great potential of applications of the FT-SAW device based strain sensors on flexible glass substrates.