The growing demand for polymer sensing surfaces with specific and improved properties has catalyzed the development of new methods of polymer synthesis and processing that provide control at the micro and nanometer scales. As illustrated by the microelectronics industry, the performance potential of these macromolecular surfaces will ultimately be related to the complexity and number of interconnections that can be achieved. However, existing techniques for the preparation of polymer surfaces are limited and new coating technologies are required. Rapid Expansion of Supercritical Solutions (RESS) is a spray-on deposition technique that takes advantage of the enormous solubility change that occurs in a rapidly expanding supercritical solution in order to form surfaces consisting of particles with narrow and tunable size distributions and morphologies. We have been utilizing RESS to deposit siloxane-based micro and nanoparticles onto the sensing surface of microfabricated Surface Acoustic Wave (SAW) transducers. We have shown that particle size and morphology can be controlled by adjusting RESS expansion parameters. The mechanical properties of developed surfaces are controlled through network formation using room temperature vapor phase crosslinking. The resulting miniature chemical sensor was tested upon exposure to organic vapors and exhibits sensitive, fast, reversible response.
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