Thermal contributions to the bending of bimaterial cantilever sensors

Abstract

The thickness dependent contribution of thermal expansion and surface potential to the thermal response behavior of polymer coated micromechanical cantilevers is investigated. Polystyrene films in a thickness range of 2–150nm are used as coatings on silicon micromechanical cantilever arrays. Depending on coating thickness, either thermal expansion or interfacial tension dominates the response. For thick films we obtain a thermal expansion coefficient of 2.3×10−5±1.0×10−5°C−1 for the polystyrene coating. Using this value a temperature coefficient of interfacial tension of −50×10−5±14×10−5Jm−2°C−1 is determined for the silicon oxide/polystyrene interface. This establishes a method to measure the temperature coefficient of interfacial tension at solid/solid interfaces.