A model for the determination of the dimensions of dents for jagged electrodes in electrowetting on dielectric microsystems.

The motion of a droplet from one electrode to the next in electrowetting on dielectric microsystems is not straightforward. Microfabrication imposes a gap separating the electrodes. This hydrophobic gap has the effect of pinning the triple contact line, preventing the motion of the microdrop. To avoid such a drawback, jagged electrodes, i.e., electrodes with crenellated side boundaries have been designed. In this work, an analytical model for dimensioning the size of the dents of the electrodes is derived based on the contact line elasticity theory. This model determines a lower limit for the nondimensional ratio of the length of a dent to its width. The designs of jagged electrodes in the literature have been verified to satisfy the condition, but with very different safety margins.