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294 MICROSENSORS
Figure 8.61 PolFET vapour sensor: (a) basic structure, (b) array of four polymer-coated n-channel
MOSFETs, (c) typical dynamic response to pulses of ethanol vapour in air, and (d) isotherms of
two polymers for ethanol and toluene. From Covington et al. (2000)
a conducting polymer FET (polFET) gas sensor and its response (c) to pulses of ethanol
vapour in air (Covington et al. 2000).
The poly(pyrrole)/butane sulfonic acid (BSA) PolFET has a voltage sensitivity of
0.8 uV/PPM to ethanol and the poly(bithiophene)/TBATFB PolFET has a sensitivity
of-0.7 uV/PPM to toluene - its behavior is well described by the Langmuir isotherm.
