Electrowetting-based actuation of droplets for integrated microfluidicsElectronic supplementary information (ESI) available: six videos showing droplet flow, droplet dispensing and electrowetting. See http://www.rsc.org/suppdata/lc/b1/b110474h/

TLDR

Control of fluid motion is essential for the serviceability of microfluidics‑based lab‑on‑a‑chip systems. The study presents an electrowetting‑based alternative to conventional microfluidics for manipulating discrete aqueous droplets. A simple open device with opposing planar electrodes on glass allows positional and formative control of nanoliter to microliter droplets at 15–100 V, offering a highly flexible and reconfigurable platform. Droplets are transported rapidly (>10 cm s⁻¹) with velocities largely independent of size, enabling small droplets to move over 1000 times their length per second, and the system also supports formation, mixing, and splitting, demonstrating electrowetting’s potential for highly integrated and flexible microfluidics.

Abstract

The serviceability of microfluidics-based instrumentation including 'lab-on-a-chip' systems critically depends on control of fluid motion. We are reporting here an alternative approach to microfluidics based upon the micromanipulation of discrete droplets of aqueous electrolyte by electrowetting. Using a simple open structure, consisting of two sets of opposing planar electrodes fabricated on glass substrates, positional and formational control of microdroplets ranging in size from several nanoliters to several microliters has been demonstrated at voltages between 15-100 V. Since there are no permanent channels or structures between the plates, the system is highly flexible and reconfigurable. Droplet transport is rapid and efficient with average velocities exceeding 10 cm s(-1) having been observed. The dependence of the velocity on voltage is roughly independent of the droplet size within certain limits, thus the smallest droplets studied (approximately 3 nl) could be transported over 1000 times their length per second. Formation, mixing, and splitting of microdroplets was also demonstrated using the same microactuator structures. Thus, electrowetting provides a means to achieve high levels of functional integration and flexibility for microfluidic systems.