Cross-Linked PDMS Expansion Due to Submersion in Liquid and Supercritical CO2

Characterization of micro/nano-copper particles impregnated Polydimethylsiloxane (PDMS) submersed in supercritical carbon dioxide (scCO2) was studied. The purpose of this investigation was to advance micro-corrosion sensor technology utilizing PDMS and micro-metal particle composite as the sensing element currently under-development. One of the key challenges encountered was the removal of the native oxides inherently existing on the metal particles. Numerous techniques were experimented with to counter this problem at the UA Engineered Micro/Nano Systems Laboratory (EMNSL), with swell-based protocols being identified as the most promising solution. In terms of compatibility to Micro-electro-mechanical Systems (MEMS) fabrication, CO2 is often used in the release of stiction for sensitive microstructures. The experimental method was classified as low temperature techniques (less than 100 degrees Celsius). Commonly, the composite exhibits expansion ratio from 2.5% to 20%, exhibiting more sensitivity to the percentage content of the metal particles, albeit below those reported in literature for pure cross-linked PDMS. The expansion time-constant is found to be on the order of 100 to 1000 seconds