Enhanced Droplet Mixer by LDEP on Spiral Microelectrodes

We demonstrated a micromixer in which a liquid column was pumped in a virtual channel without channel walls by LDEP. Two droplets were first transported and joined together by EWOD actuation. The small contact area at the interface of the merged droplet and the long diffusion distance caused long mixing time by merely diffusion. A spiral-shaped LDEP electrode was designed to draw a thin liquid column from the merged droplet at the interface in order to increase the contact area and reduce the diffusion distance. Since no channel walls were required for LDEP pumping, the spiral-shaped liquid column would merge together again to form a new droplet for further analyses.