Material Selection and Design of Microelectrothermal Actuators

Thermal bimorphs are commonly used microelectrothermal actuators due to the simplicity of their micro fabrication and their ability to achieve out-of-plane actuation. We present a strategy for identifying suitable candidate materials to improve the performance of thermal bimorph actuators using an analytical framework. The performance metrics considered are maximum work/volume, blocked moment and free end slope. Optimal performance and the corresponding thickness ratio were evaluated for pairs of materials. Contours of equal performance corresponding to arbitrary materials on silicon when compared using Ashby's selection map reveal engineering alloys/metals (Zn, Mg, Cu, Ni and Steel) and polymers (Epoxies, PDMS, MEL, PMMA) which have not been considered previously for thermal bimorph actuators. The accompanying methodology can be used for different substrate materials to identify novel material combinations which merit further research.