We report on the deployment of MEMS static bifurcation (DC) sensors for the detection of volatile organic compounds (VOCs): hydrogen sulfide and formaldehyde. We demonstrate a sensor that can detect as low as a few ppm of hydrogen sulfide. We also demonstrate a sensor array that can selectively detect formaldehyde in the presence of benzene, a closely related interferent. Toward that end, we investigate the sensitivity and selectivity of two detector polymers—polyaniline (PANI) and poly (2,5-dimethyl aniline) (P25DMA)—to both gases. A semiautomatic method is developed to functionalize individual sensors and sensor arrays with the detector polymers. We found that the sensor array can selectively sense 1 ppm of formaldehyde in the presence of benzene.
A resonant
microcantilever sensor is fabricated from a zinc oxide
(ZnO) thin film, which serves as both the structural and sensing layers.
An open-air spatial atomic layer deposition technique is used to deposit
the ZnO layer to achieve a ∼200 nm thickness, an order of magnitude
lower than the thicknesses of conventional microcantilever sensors.
The reduction in the number of layers, in the cantilever dimensions,
and its overall lower mass lead to an ultrahigh sensitivity, demonstrated
by detection of low humidity levels. A maximum sensitivity of 23649
ppm/% RH at 5.8% RH is observed, which is several orders of magnitude
larger than those reported for other resonant humidity sensors. Furthermore,
the ZnO cantilever sensor is self-actuated in air, an advantageous
detection mode that enables simpler and lower-power-consumption sensors.
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