Selectivity of chemical sensors based on micro-cantilevers coated with thin polymer films

In an effort to impart selectivity to chemical sensors based on micro-machined silicon cantilevers, thin films of polymeric chromatographic stationary phases (SP-2340 and OV-25) were applied to one side of the cantilever surface using a spin coating procedure. These coatings influenced the response of the micro-cantilever to vapor phase test analytes of varying chemical compositions. For the SP-2340 coated micro-cantilevers, the effects of both polymeric film thickness and cantilever structure thickness on response characteristics were investigated. Sensitivity improved as both film thickness and cantilever leg thickness were decreased. The selectivity, as indicated by differences in relative responses to the test analytes, were different for the two phases which differed significantly in polarity. The SP-2340 coated cantilevers exhibited response characteristics that an fairly similar to that expected for adsorption of the test analytes onto silica. Responses are shown to be proportional to analyte concentration. Response characteristics are shown to be consistent with predictions based on a gas chromatographic stationary phase classification scheme. (C) 2000 Elsevier Science B.V. All rights reserved.