Full text loading...
An electrothermally activated micro-positioner using high-aspect-ratio micromachined polymer composite of silicon and SU-8 epoxy: (a) a scanning electron micrograph (SEM) of a micromachined chip of the micro-positioner with two thermal unimorphs (on the contact pad are residues of carbon adhesive for attaching the device on a sample holder of SEM); (b) a schematic drawing showing that activation of a thermal unimorph in the micro-positioner moves a slider on a flexural stage by a lateral stroke u(t); (c) photograph of a thermal unimorph, which consists of a comb-like silicon skeleton, a U-shape platinum heater, and transparent SU-8 polymer filling.
Displacement of the slider, when driven by the micro-positioner, which has one of the two thermal unimorph activated by pulsed heating at a 50% duty cycle: (a) activation by a square voltage pulse with 4 V magnitude and 0.5 ms pulsewidth; (b) activation by a square voltage pulse with 4 V magnitude and 1 ms pulsewidth. (c) peak-to-peak stroke of the actuated slider as a function of pulsewidth and magnitude of a square voltage pulse. The time constants of the thermomechanical response are obtained by least-square fitting the experimental data using the exponential equations of time, as indicated besides the curve-fit lines.
Temperatures of the two unimorphs, one activated under pulsed resistive heating and one inactivated. The temperatures are estimated from the resistance change of each heater: (a) temperature change of left heater (), right heater (), and their difference () over time under a 4 V and 6.1 ms voltage pulse; dependences of peak-to-peak temperature difference () on (b) pulsewidth and (c) voltage.
Frequency response of the slider, which is actuated by two thermal unimorphs under alternate activation with a half-sine pulse. The in-plane motion of the slider is measured by a laser doppler vibrometer.
Article metrics loading...