A Chemical Sensor Based on a Micromechanical Cantilever Array for the Identification of Gases and Vapors

We have built and operated a novel setup for the characterization and identification of gases or vapors based on sequential position readout via beam-deflection technique from a microfabricated array of eight cantilever-type sensors. Each of the cantilevers can be coated on one side with a different sensor material to detect specific chemical interactions. We demonstrate that disturbances from vibrations and turbulent gas flow can be effectively removed in array sensors by taking difference signals with reference cantilevers. For example, hydrogen can be detected by its adsorption onto a platinum-coated sensor because a change in surface stress causes a static bending of the sensor. The diffusion of various alcohols into poly-methyl-methacrylat induces resonance frequency shifts in a dynamic measuring mode and bending in the static mode, which allows one to distinguish among the various alcohols.