An electrothermal microactuator with Z-shaped beams

This paper introduces a Z-shaped thermal microactuator for in-plane motion, which could be complementary to the well-established comb drives and V-shaped thermal actuators. The Z-shaped actuators share many features in common with the V-shaped ones, but offer certain advantages such as smaller feature size and larger displacement. They also offer a large range of stiffness and output force that is between those of the V-shaped actuators and comb drives. In particular, they can achieve smaller stiffness without buckling, which renders them as simultaneous load sensors. The Z-shaped actuator was modeled analytically and verified by multiphysics finite element analysis. Among all the design parameters, the beam width and the length of the central beam were identified as the major ones in tuning the device displacement, stiffness, stability and output force. Experimental measurements of three arrays of Z-shaped thermal actuators agreed well with the finite element analysis. In addition, the quasi-static and dynamic performances of individual Z-shaped thermal actuators were measured. The average temperature in the device structure was estimated from the electric resistivity at each actuation voltage. The bandwidth of the Z-shaped thermal actuators can be increased for devices with a substrate underneath.