Nanomechanical characterization of polymer beam structures for BioMEMS applications

Polymer microstructures are incorporated in biomicroelectromechanical system (BioMEMS) devices with applications ranging from drug screening to defense applications. Nanomechanical characterization of the polymer components must be carried out in order to design reliable devices. This paper presents the nanoindentation characterization of polymer beams fabricated through soft lithography-based techniques for BioMEMS applications. Poly(propyl methacrylate) (PPMA), poly(methyl methacrylate) (PMMA), polystyrene (PS) and a nanocomposite of polystyrene and clay (PS/Clay) were investigated in this study. The hardness, elastic modulus and creep behavior of microbeams made from these materials were measured using continuous stiffness measurement (CSM) nanoindentation, and the scratch resistance of thin films was measured using a nanoscratch technique. Yield and breaking strengths were determined by normal beam bending at elevated loads, in which the presence of the nanoclay filler in the composite modified the deformation behavior relative to the unfilled polystyrene. Lateral bending of PS and PS/Clay cantilever beams is demonstrated for the first time. The mechanical response of beams after soaking in deionized water or heating to human body temperature was examined.