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Humidity sensor based on conductivity measurements of a poly(dimethyldiallylammonium chloride) polymer film

1993; Elsevier BV; Volume: 17; Issue: 1 Linguagem: Inglês

10.1016/0925-4005(93)85184-c

1873-3077

Karen L. Rauen, D.A. Smith, William R. Heineman, Jay M. Johnson, Russell Seguin, Paul Stoughton,

Conducting polymers and applications

In order to explore further the properties of the ionically conductive polymer poly(dimethyldiallylammonium chloride (poly(DMDAAC)), a relative humidity (RH) sensor based on conductivity measurements has been fabricated. This sensor consists of a platinum conductivity cell, comprising four parallel platinum 'finger' electrodes on a 25.4 mm × 25.4 mm × 0.64 mm ceramic wafer. Two glass masks provide a reproducible sensing area. The wafer is spin-coated with a thin poly(DMDAAC) film and subsequently crosslinked with a 10 Mrad gamma-irradiation dosage using a 60Co source. The sensor exhibits a nonlinear conductivity response to RH in the 20–80% range. A steady-state response to an RH change of 12 to 50% occurs within 1–2 min. The conductivity varies with film thicknesses ranging from 0.5–30 μm. For example, conductivity values obtained at 97% RH are 147.9 μmho for a 30 μm film, compared to 26.5 μmho for a 0.5 μm film. Sensors show a 0.–30% decrease in conductivity after continuous exposure to ambient laboratory atmosphere for 15 months.