In this paper we disclose how to contour the beams of micro-scale thermomechanical actuators (TMAs) in order to enhance the actuator’s thermal and mechanical performance. In this approach, we vary the cross section of the driving Joule heated beams over the length of the beam. Using this approach, (1) the stored mechanical energy and axial stiffness of beam may be modified to achieve an optimized force-displacement relationship, (2) the maximum achievable thermal strain of a driving beam may be increased by 29%, (3) actuator stroke may be increased by a factor of 3 or more, (4) identical force or displacement characteristics may be achieved with 90% reduction in power. This paper presents the theory and models used to predict the thermal and mechanical behavior of the actuator. The theory and models were used to create a deterministic link between the actuator’s design parameters and the actuator’s performance characteristics. The theory and models were combined within a design tool that shows less than 5% error from non-linear Finite Element Analysis simulations. The design tool has been used to generate plots that enable designers to (1) understand the qualitative relationships between design parameters and performance and (2) select first-pass design parameters. The theory was used to create a design tool, posted at http://psdam.mit.edu, that may be used to perform qualitative design assessment and optimization.

Volume Subject Area:
Microelectromechanical Systems
Topics:
Actuators, Design, Optimization, Thermomechanics, Displacement, Engineering simulation, Equipment performance, Errors, Finite element analysis, Joules, Mechanical behavior, Microscale devices, Performance characterization, Simulation, Stiffness
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