Graphical design for thin-film SMA microactuators

Abstract

Simple graphical designs for bridge- and diaphragm-type actuators usingshape-memory alloy (SMA) thin films are proposed. The performance(force and displacement) of these actuators is predicted on the basis of thestress–strain curves of an SMA film by introducing the material parameterK that represents the mechanical properties of both the austenite and martensitefilms. The methods of designing actuators are presented along with numericalexamples and their validity is discussed, referring to some actual devices suchas a microvalve and a micropump. A comparison of theory and actual deviceperformance shows that the proposed design gives a useful approximation for practicalapplications. The advantage of the proposed design method is that, once the value ofK is obtained for a given SMA film, one can design various actuators with various dimensionswithout detailed information about its mechanical properties.