Chemical Sensing Through Measurement of Thickness/Impedance Characteristics of Ion-Conducting Polymer Films

Abstract

A chemical microsensor system capable of simultaneously measuring the impedance and thickness of thin polymer films exposed to analyte vapors is described. The system is constructed from a quartz substrate with interdigitated electrodes and a piezoresistive microcantilever. Measurements of the thickness and impedance of 10-30 μm thick films of LiClO4LiClO4 doped polyethyleneoxide (PEO) exposed to water, ethanol, acetone, and n-octane are reported. Experiments show that the thickness and impedance measurements are complementary and that thickness/impedance profiles allow the identification and quantification of the analytes tested. Scanning force microscopy (SFM) shows that PEO lamellae become smaller as the level of LiClO4LiClO4 doping increases. SFM also shows an increase in the amount of amorphous material increases when doped PEO is exposed to water vapor. The uniqueness of the thickness/impedance profiles for the analytes is discussed in terms of the SFM results. © 2003 The Electrochemical Society. All rights reserved.