MEMS chemical gas sensor

We have developed a miniature polymer-based chemical gas sensor array on silicon using micromachining technology. The sensors use conductive polymer-carbon black composite films, which swell reversibly and induce a resistance change upon exposure to a wide variety of gases. Using a SU-8 photoresist, we have constructed high aspect ratio wells which can contain the polymer-carbon black-solvent liquid volume present during deposition and allow the sensor film to be placed reproducibly in a specific and well-constrained area while reducing its overall size. Two sizes of wells, 500/spl times/600 /spl mu/m and 250/spl times/250 /spl mu/m, have been fabricated and tested. Six polymer-carbon black composite films were deposited into an array of sensor wells and exposed to three chemical gases at five concentration levels. The sensors were able to uniquely detect these gas vapors and demonstrated a linear response to the concentration levels. This design allows the integration of circuits to process the changes in resistance which will permit the realization of a completely integrated miniature gas sensor.