Dynamics of the electro-osmotically toggled droplet switch

A capillary switch is a bi-stable system of liquid/gas interfaces with a trigger to toggle back and forth between the energy wells. The electro-osmotic droplet switch consists of a pair of coupled droplets whose shape-change is triggered by volume transfer using an electro-osmotic pump placed between the droplets. With the pump off, the stable states are a pair of identical sub-hemispherical drops for low total-volume or a large-small droplet configuration(two mirror-symmetric states) for large enough total-volume. With the pump on, these stationary states are shifted or there are no stationary states at all, depending on the pump strength. We report the pump-on behavior as a modification of the pump-off behavior. A dynamic model of the system which adopts an Ergun-equation characterization of the pump is introduced. Model predictions are compared to observation.