Surface-tension-driven microactuation based on continuous electrowetting

TLDR

The study presents the first MEMS device that harnesses surface tension via continuous electrowetting, aiming to translate this principle into practical microactuation. The device drives a liquid‑metal droplet in an electrolyte‑filled capillary by locally altering surface tension with an applied voltage, addressing material compatibility, electrode polarization, electrolysis, and micromachining challenges. Initial tests show a smooth, wear‑free liquid micromotor rotating at ~40 mm s⁻¹ (420 r min⁻¹) around a 2‑mm loop, powered by only 2.8 V and consuming 10–100 µW.

Abstract

This paper describes the first microelectromechanical systems (MEMS) demonstration device that adopts surface tension as the driving force. A liquid-metal droplet can be driven in an electrolyte-filled capillary by locally modifying the surface tension with electric potential. We explore this so-called continuous electrowetting phenomenon for MEMS and present crucial design and fabrication technology that reduce the surface-tension-driving principle, inherently powerful in microscale, into practice. The key issues that are identified and investigated include the problem of material compatibility, electrode polarization, and electrolysis, as well as the micromachining process. Based on the results from the initial test devices and the design concept for a long-range movement of the liquid-metal droplet, we demonstrate a liquid micromotor, an electrolyte and liquid-metal droplets rotating along a microchannel loop. Smooth and wear-free rotation of the liquid system is shown at a speed of /spl sim/40 mm/s (or 420 r/min along a 2-mm loop) with a driving voltage of only 2.8 V and little power consumption (10-100 /spl mu/W).