3D electrowetting-on-dielectric actuation

•3D digital microfluidics based on electrowetting-on-dielectric (EWOD) actuation is proposed and experimentally verified.•The dynamic behavior of a droplet under various EWOD conditions such as different applied frequencies and switching times is studied using high-speed imaging.•The first complete 3D droplet manipulation through the combination of horizontal and vertical actuation between two parallel plates is experimentally achieved by sole EWOD actuation.

This paper describes three-dimensional (3D) digital microfluidics based on an alternating current electrowetting-on-dielectric (AC-EWOD) principle. To achieve 3D manipulation of a droplet between two parallel plates, the horizontal and vertical actuation of a droplet is investigated separately. The dynamic behavior of a water droplet actuated by AC-EWOD in various conditions is studied using high-speed imaging. Optimum actuation parameters such as applied frequency, switching time, and the gap between the top and bottom plates are obtained. For horizontal actuation, a high frequency (1 kHz) is used for small-droplet deformation; on the other hand, for vertical actuation, a low frequency (44 Hz) is used for large-droplet deformation. Finally, as a proof of concept, 3D manipulation of a droplet with two parallel plates is demonstrated by the combination of horizontal and vertical AC-EWOD actuation, resulting in increased space for digital microfluidics.