The impact of materials selection and geometry on multi-functional bilayer micro-sensors and actuators

This paper details the impact of thermomechanical properties on the multi-functional performance of sensors and actuators composed of two different layers: temperature sensors, pressure/force sensors, chemo-mechanical sensors, electrostatic actuators, etc. The models quantify the coupling between physical inputs and deformation of freestanding structures, such as bending of cantilevers and buckling of bilayers. A comparison of material systems based on emerging polymeric microfabrication techniques illustrates that significant increase in sensitivity can be achieved by combining polymeric structures with either micro-patterned metal or conductive polymer electrodes. Moreover, the use of compliant materials enables new types of devices designed to exploit buckling phenomena. Results are included for the post-buckling displacements of bilayers subjected to non-uniform temperature changes, surface stress and swelling-induced strains. Microfabrication targets for soft materials (notably film thickness to span ratios) are identified which will greatly advance the state-of-the-art.