Vapor detection using resonating microcantilevers

Changes in the resonance frequency of microcantilevers due to adsorption of analyte vapor on exposed surfaces is shown to provide a novel means for detection of the analyte. Frequency changes can be due to mass loading or adsorption-induced changes in cantilever spring constant. Sensitization to water vapor is demonstrated by coating cantilever surfaces with hygroscopic materials, such as phosphoric acid. Cantilevers coated with a thin gelatin film exhibit high sensitivity and a linear response with changes in relative humidity, apparently due to changes in the spring constant of the coated cantilever. In addition to frequency response, static cantilever deflection also changes with vapor adsorption. Both phenomena can be used to detect adsorbed vapors with picogram mass resolution.