New Sensing Materials for SAW Sensors Using Polymer-Silicate Composites

We present a new type of sensitive coating materials by using polymer-silicate composites as sensing layers on surface acoustic wave (SAW) sensors. Initial layers thereof were prepared by spin coating of sol-gel precursors resulting in covalently bound self-organized and stable porous surface structures. In a next step the same but pure polymer solution is used to prepare a second layer capable to semi-selectively absorb gases. Since the applied curing temperature is below 100degC the composites still contain the polymer. The first layer then initiates a controlled structural dewetting of the second layer towards cavities dominated by polymer residuals in the composite. The result is a very stable binding of the additional polymer leading to sensing materials with high longevity. Properties and sensing characteristics of layers using tetra-ethoxysilane and triethoxyfluorosilane as silicate precursors with the sensing polymer polyisobutylene are discussed.