Ultra high frequency acoustic wave propagation in fully polymer based surface acoustic wave device

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Surface acoustic wave (SAW) device, which integrates the generation, propagation and detection of acoustic waves into the same device, has been known to be an essential functional unit for sensors and electromechanical systems. However, high substrate cost and process complexity of traditional inorganic SAW devices have triggered extensive research efforts to seek for alternative low cost solution, especially for disposable application. Poly(vinylidenefluoride)[P(VDF)] and its co-polymer, despite being promising materials for acoustic transducer with inexpensive processing technique, have rarely been used in SAW device due to exhibiting extremely low operating frequency (few tens of MHz) compared to the traditional SAW device (few hundreds of MHz to GHz) based on inorganic piezoelectric material. Here we demonstrate SAW device, which is entirely based on Poly(vinylidenefluoride-trifluoroethylene) [P(VDF-TrFE)], as piezoelectric material, offering transduction and propagation of acoustic waves with a frequency around 450 MHz. The drawbacks of the previous attempts by the others are addressed and rectified systematically to obtain high operating frequency comparable to the traditional SAW. The influence of periodicity of interdigitated transducer and thickness of polymer film on device performance is thoroughly investigated. Temperature dependent variation of resonance frequency, which can be exploited as temperature sensor in integrated systems, is also demonstrated.