A digital microfluidic modular interface (chip-to-chip interface) which possesses an electrode with an orifice to vertically transport core-shell droplets is presented. The electrodes were geometrically designed to promote droplet deformation and suspension. The droplets were then applied with an electrical potential for insertion into and passage through the orifice. The concepts were tested with three types of droplets at the volume of 0.75~1.5 μL, which is usually difficult to transfer through an orifice. The integration of electrowetting on dielectric (EWOD) with paper-based microfluidics was demonstrated: the droplet could be transported within 10 s. More importantly, most of the core droplet (~97%) was extracted and passed through with only minimal shell droplets accompanying it.
Keywords: chip-to-chip interface; electrowetting on dielectric (EWOD); orifice; paper microfluidics; water–oil separation.