Fast temperature programmed sensing for micro-hotplate gas sensors

We describe an operating mode of a gas sensor that greatly enhances the capability of the device to determine the composition of a sensed gas. The device consists of a micromachined hotplate with integrated heater, heat distribution plate, electrical contact pads, and sensing film. The temperature programmed sensing (TPS) technique uses millisecond timescale temperature changes to modify the rates for adsorption, desorption, and reaction of gases on the sensing surface during sensor operation. A repetitive train of temperature pulses produces a patterned conductance response that depends on the gas composition, as well as the temperature pulse width, amplitude, and specific sequence of pulses. Results are shown for the vapors of water, ethanol, methanol, formaldehyde, and acetone.