Owen E. Brown


The thermal bimorph actuator is a multi-layer Micro-Electro-Mechanical (MEMS) device used to achieve out-of-plane mechanical displacements in response to a thermal input. This device is one of the simplest MEMS devices to manufacture. Previous investigations of thermal bimorph actuators have studied the best materials to use based on ease of deposition, and the overall effect on the devices. The current work presents an optimization of the thermal bimorph (Aluminum and Polysilicon) actuator geometry, for a target application of a micro robotics actuator. The application of bimorph actuators to micro robotics demands high efficiency in the conversion from thermal energy to mechanical displacement, since low efficiencies require larger power supplies and reduce the payload capacity of the the micro-robot. Two subsystems with significant impact on bimorph actuator efficiency include the thermal mass of the substrate (modeled with three parameters) and the relationship between various geometrical dimensions (modeled with four parameters) of the actuator leg. Each subsystem is optimized using a transient finite element analysis of the coupled thermal and mechanical response. Parametric studies were used to investigate the response curve of the target functionals and then optimized using a local steepest descent algorithm. The optimized system results in a nominally 200 % higher payload capacity with 350 % stiffer mechanical characteristics. Results of the investigation demonstrate the need for more accurate material properties at the micro-scale. The mass of the power supply required to achieve sustained micro robot motion using thermal bimorph actuators currently exceeds the corresponding payload capacity of the device.

Library of Congress Subject Headings

Bimorphs; Microelectromechanical systems; Microactuators; Robots--Control systems

Publication Date


Document Type


Student Type


Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering (KGCOE)


Wayne Walter

Advisor/Committee Member

Ferat Sahin

Advisor/Committee Member

Satish Kandlikar


Physical copy available from RIT's Wallace Library at QC595 .B76 2006


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