Design and fabrication of an electro-thermal microactuator with multidirectional in-plane motion

Abstract

We present a new electro-thermal microactuator with multidirectional in-plane motion by selectively applying a single potential across two of four contacts. The design principle is based on the asymmetrical thermal expansion of the structure with 1. different lengths and widths of the beams, 2. varying resistivities of the beams by selectively doping, and 3. rigorous control of the thermal boundary conditions. Analytical models are derived to describe the electro-thermo-mechanical performances of the actuator. The commercial finite element package ANSYS is used to demonstrate the feasibility of the design, to verify the analytical results, and to characterize the actuator in details under complex heat transfer conditions. The design parameters that significantly affect the performance of the actuator are discussed, including the structural dimension, selective doping, and heat transfer condition. Conventional silicon-based micromachining techniques compatible with IC processes are used to fabricate the microactuator. The phosphorous-doped polycrystalline silicon film by low pressure chemical vapor deposition ͑LPCVD͒ is used to demonstrate the effectiveness of the microactuator. In conclusion, it is found that input voltages ഛ7 V are required for the microactuator to achieve the maximum displacement in 8 m and the maximum tip force in 8 N with the operating temperature below 300°C, the power as low as 10 mW, and the response time about 30 msec in average.

An experimentally verified model for thermal microactuators including nonlinear material properties, vacuum, and intra-device heat conduction

“…a cde eq (15) The arms of the microactuator are sufficiently slender such that the temperature variation within each cross section can be considered negligible with respect to temperature variation along the length of each arm. A coordinate, s, is therefore introduced to represent the axial distance from the terminal of the hot arm, following the axis of each arm around the actuator, as shown in figure 1(a).…”