Abstract
This paper reports a novel method for detecting ethylene by using KMn04/polyimide composite thin-films as the analyte-sensitive layer in a capacitive MEMS ethylene sensor which requires zero-DC power for reliable operation. The technique utilizes a MEMS parallel-plate capacitor with the thin-film as a dielectric layer. Exposure of ethylene to the KMnO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> molecules embedded within the polyimide matrix results in oxidation of ethylene into CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> 0, which induces swelling of the thin-film and also changes its dielectric-constant. This leads to a change in device capacitance. Preliminary results indicate a nearly reversible linear decrease of sensor capacitance of ~1 - 14 pF when exposed to ethylene concentrations ranging from 130 - 1000 ppm, yielding a normalized capacitance sensitivity of ~3.74×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−6</sup> /ppm. Selectivity tests revealed a favorable response towards ethylene compared to gases such as hexanal, indole, pentane, acetone, and IPA.
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