Droplet ejection by electrowetting actuation

Fast contact-line motion of a droplet spreading on a solid substrate under the electrowetting effect generates strong capillary waves on the droplet's surface. The capillary waves may be strong enough to induce ejection of a satellite droplet from the primary one. In this study, we show that the size of the satellite droplet and the ejection time are not only dependent on the contact-line velocity, which directly relates to the applied voltage enabling the electrowetting effect, but are also affected by the ejection dynamics. We derive a theoretical model of the criteria for droplet ejection and experimentally verify the proposed criteria for wide ranges of viscosity, droplet size, and the applied voltage.

Automated summary

Under the electrowetting effect, fast contact-line motion generates strong capillary waves on a droplet's surface, potentially leading to the ejection of satellite droplets. The size and ejection time of the satellite droplets are not only dependent on the contact-line velocity, but also influenced by the ejection dynamics.