Tan, Su-Lim, Covington, James A., 1973- and Gardner, Julian W.. (2006) Velocity-optimized diffusion for ultra-fast polymer-based resistive gas sensors. IEE Proceedings - Science, Measurement and Technology, Vol.153 (No.3). pp. 94-100. ISSN 1350-2344

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Abstract

Conducting polymers are an attractive candidate for use in thin film resistive gas and vapour sensors, but their use has been limited by their apparently slow response times ranging from tens of seconds to minutes. In studying this problem, the authors have discovered that the response time is highly dependent upon the velocity at which the analyte flows across the sensor surface. This type of sensor operates at ambient temperature, and so the authors have attributed this behaviour to the combination of a reduced time for diffusion of the analyte in the carrier gas (pulse broadening) and faster diffusion through a disturbed boundary layer on the polymer surface. A finite element model has been developed to explore this phenomenon. The actual responses of two types of carbon-black/polymer composite resistive sensors have been measured. at velocities ranging from 50 to 1500 cm/s to pulses of ethanol and toluene vapour in air, using a purpose-built automated low-volume microchannel flow delivery system. The effect of velocity on the sensors response has been found to vary for different analytes, with a linear velocity,coefficient of 1 to 15 s/cm for ethanol and toluene vapour in air, respectively in the diffusion coefficient. The magnitude and rise time of the sensor responses were computed for different velocities and agrees well with the theoretical finite element model. Under optimal conditions, the fastest sensor was found to exhibit a rise time of less than 100 ms, which would be expected to fall even further for thinner films. These results suggest that conducting polymer resistive sensors could be designed to work with a 1 s duty cycle making them attractive for applications where rapid monitoring is required, e.g. on unmanned airborne vehicles and land-based mobile robots.

Item Type:	Journal Article
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions:	Faculty of Science > Engineering
Journal or Publication Title:	IEE Proceedings - Science, Measurement and Technology
Publisher:	Institute of Engineering Technology
ISSN:	1350-2344
Date:	May 2006
Volume:	Vol.153
Number:	No.3
Number of Pages:	7
Page Range:	pp. 94-100
Identification Number:	10.1049/ip-smt:20050035
Status:	Not Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
URI:	http://wrap.warwick.ac.uk/id/eprint/33449

Data sourced from Thomson Reuters' Web of Knowledge

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