Electrowetting Characteristics of an Insulating Droplet under Coplanar Electrode

Abstract

Abstract Electrowetting on dielectric (EWOD) has become an effective droplet manipulation method in microfluidic technology. In this paper, a theoretical model based on energy conversation is established to depict the electrowetting behavior of an insulating droplet located on a coplanar electrode in conductive liquid. To validate the correctness of the theory, COMSOL is carried out to simulate wettability evolution of the silicone oil droplet surrounded by propylene glycol (PG) containing with 1 wt% tetrabutylammonium chloride (TBAC). Relative experiments are conducted to detect the contact angle (CA) and height (H) of the insulating droplet at different voltage. When the voltage is increased, the wettability of the conductive liquid changes and consequently the insulating droplet is squeezed inward. The silicon oil droplet in PG exerts continuous change in CA and H by operation of voltage adjustment. When the voltage is increased to 110V, the CA changes from 42.5° to 134°, and the relative H reaches up to 3.46 mm. The results show that theoretical model is basically consistent with the facts.