MEMS Sensors with Chemically Selective Coatings of Ionic Liquids

摘要

Ionic-liquid-coated cantilevers were used in this study to investigate their response to gaseous and aqueous analytes. A coating method has been developed to ensure that the cantilevers are uniformly coated. It was found that higher-viscosity ionic liquids helped to achieve a uniform coating. Furthermore, addition of nanoparticles and fabrication of nanostructures on the surface of microcantilevers were found to increase the uniformity of the ionic-liquid coatings. Deflection and oscillation frequency-shift measurements were obtained for various vapor analytes including water ethanol, acetone, carbon dioxide, ozone, and nitrous oxides in single-analyte tests. All analytes but ozone showed a strong, reproducible response, indicating a potential for ionic-liquid use in microcantilever-based detection devices. This does not mean that ozone cannot be detected by ionic liquid-coated microcantilevers. A systematic study of ionic-liquid properties can reveal better candidates for ozone detection than the ionic liquid selected in this study. Response measurements of particles and dissolved analytes in aqueous solutions were more complex than in gaseous systems. This means that the interpretation of the results in terms of the origin of the response will be difficult. However, the coated microcantilever appeared to be sensitive to the Brownian motion of the particles in the suspension and thus could potentially serve as a detector for similarly sized, non-benign waterborne particles introduced into the environment. The main conclusion of this Strategic Environmental Research and Development Program (SERDp) Exploratory Development (SEED) project is that because of their favorable physical and chemical properties, ionic liquids are in general good candidates for further investigation for use as coatings of microcantilevers, which are critical parts of microelectromechanical systems sensors.