Design and characterization of an electrothermally driven monolithic long-stretch microdrive in compact arrangement

Abstract

An electrothermally driven long stretch microdrive (LSMD) is presented for planar rectilinear motions in hundreds of micrometers. Design concept is based on connecting several actuation units in series to form a cascaded structure to accumulate relative displacement of each unit, and two cascaded structures are further arranged in parallel by a connection bar to double output force. The proposed area-saving design features monolithic compliant structure in compact arrangement to achieve long stroke. In experiments, the maximum reversible operating voltage is 3 V. In addition, the voltage-displacement relation shows good linearity within +/- 5% in 0.5-3.0 V. Fabricated nickel LSMD can generate displacement up to 215 mu m. (W = 8 mu m, theta = 0.2 degrees, D = 34 mu m) at 3 dc volts (669 mW). The maximum operation temperatures of tested LSMDs at 3 V are below 300 degrees C. Output forces up to 495 mu N are measured by in situ passive micromechanical test beams. The LSMD can be operated at 100 Hz without degradation on displacement. Two geometrical design parameters, bent angle and constraint bar width, are also investigated analytically and experimentally.