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Molecularly imprinted polyurethanes were used as sensor materials for monitoring the degradation of automotive engine oils. Imprinting with characteristic oils permits the analysis of these complex mixtures without accurately knowing their composition. Mass-sensitive quartz crystal microbalances (QCMs) coated with such layers exhibit mass effects in addition to frequency shifts caused by viscosity, which can be compensated by an uncoated quartz or a non-imprint layer. Incorporation of degradation products into the imprinted coatings is a bulk phenomenon, which is proven by variation of the sensor layer height. Therefore, the resulting sensor effects are determined by the degradation products in the oil.

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We aimed to compare the properties of high frequency, highly sensitive surface acoustic wave (SAW)-resonators and the more robust quartz micro balances (QMB) in chemical sensing. The sensitivities of both transducers to organic solvent vapors were determined. The correlation behveen sensor effects and resonant frequencies of the devices was checked using molecular cavities as sensor materials [ 1,2]. Additionally we tested the potential of another means of sensor material synthesis compatible with fabrication processes, namely the procedure of molecular imprinting [3,4,5]. Analyteadapted cavities can be generated by a polymerization process in presence of the analyte to be. An imprint of the latter is left behind in the polymer after removal of the template molecule. In this way sensitive and selective coatings can easily be generated. They are e.g.suitable for organic solvent vapor detection devices.