Statics and dynamics of an underwater electrostatic curved electrode actuator with rough surfaces

Here, we present a model, design, static and dynamic testing, and analysis of an electrostatic curved electrode actuator in deionized water. The actuator is integrated within a microfluidic device designed for high throughput cell sorting. The actuator shifts the bifurcation point of a Y-shaped microfluidic channel to simultaneously increase the width of one channel while decreasing the width of another channel, thus changing the bias in hydrodynamic resistance between outlet channels. The actuator is modeled as a clamped-roller beam and the static displacement is calculated based on Rayleigh-Ritz energy methods. The model accounts for oxide growth and surface roughness that occurs during fabrication. We observe that modeling a rough contact surface improves the maximum displacement prediction to within less than 20% error from the experimental value. Additionally, the model predicts a release voltage within less than 8% error of the experimental value. We also present dynamic experiments to test the actuator displacement at frequencies from 1 to 4096 Hz and show that the actuator achieves large displacements ( > 8 mu m) at high frequencies ( > 100 Hz).