Electrostatic potential wells for on-demand drop manipulation in microchannels
Precise control and manipulation of individual drops are crucial in many lab-on-a-chip applications. We present a novel hybrid concept for channel-based discrete microfluidics with integrated electrowetting functionality, by incorporating co-planar electrodes (separated by a narrow gap) in one of the microchannel walls. By combining the high throughput from channel-based microfluidics with individual drop control from electrical actuation we harvest the strengths of both worlds. The tuneable strength of the electrostatic forces enables a wide range of drop manipulations, such as on-demand trapping and release, guiding, and sorting of drops in the microchannel. In each of these scenarios, the retaining electrostatic force competes with the hydrodynamic drag force. The conditions for trapping can be predicted using a simple model that balances these forces.