Electrocapillary Piston Motion and a Prototype of Phase-Manipulating Micromirror

In this paper, we study the piston motion of a mercury droplet that is confined in a metal-plated microhole. This droplet is actuated by the electrocapillary effect and large displacements of up to 210 /spl mu/m are achieved with very low voltages (/spl sim/2 V). We use a high-speed camera (10,000 frames/s) to capture the piston motion and we find the resonance frequency is /spl sim/50 Hz. The mercury droplet geometry in equilibrium state is analyzed based on Laplace equation and volume conservation. A mathematical model is developed; it predicts that the resonant frequency of mercury droplet is 150 Hz. A prototype of piston-motion micromirror is also demonstrated in the experiment, with a frequency of 400 Hz and amplitude of /spl sim/8 /spl mu/m at 2 V.