Micromechanical active amplifiers using the mechanical resonance modulated by motion-dependent stiffness

Abstract

This thesis presents micromechanical active amplifiers for high-sensitive microsensors and high-force actuators. The previous micromechanical passive amplifiers use lever mechanisms without energy sources, thus unable to amplify both displacement and force. The present devices, however, use carrier motion actuators (energy source) to apply the mechanical resonance modulated by variable springs, thereby amplifying displacement and force simultaneously. We design, fabricate, and characterize two types of the micromechanical active amplifiers, where we connect two different variable springs to the carrier motion actuators. The two variable springs have the identical initial stiffness of 10.2 ±0.8N/m while the variable springs A and B are designed to increase the stiffness change (0~1.69N/m) by the input motion (0~0.945μm) and to decrease the stiffness (2.37N/m) of the input part, respectively. The carrier motion actuators generate the identical resonant motion of 8.06±0.11μm at the different frequencies of 16.95kHz and 18.5kHz in the micromechanical active amplifiers A and B, respectively. In the experimental study of the micromechanical amplifiers, we verify that the present devices amplify both displacement and force: The amplifier A shows the displacement and force gains of 5.62 and 7.92 at the nonlinearity of 2.26% for the input motion of 0~0.945μm; The amplifier B shows the displacement and force gains of 2.62 and 11.6 at the nonlinearity of 1.52% for the input motion of 0~1.08μm. These results also indicate that the amplifier A has the higher displacement gain and the lower force gain compared to the amplifier B. We also characterize the motion interference in the amplifiers. In this characterization, we verify that the amplifier B, whose variable spring has small input stiffness, can reduce the motion interference: The carrier motions induce unwanted input motions of 0.214μm and 0.031μm in the amplifiers A and B, respectively; The input motions in...