Mechanism of Electrohydrodynamic Flow in AC Electrowetting

AC 전기습윤 중 전기수력학 유동의 메카니즘

In AC electrowetting, it has been reported that there is a flow inside droplets. The flow characteristics such as flow rate, direction and the pattern of streamline are altered according to the frequency range of applied voltage. However, the mechanism of the flow has not been explained yet. This work is concentrated on investigation of the flow mechanism when high-frequency voltage is applied to droplets. We propose that this phenomenon arises from the electro-thermal flow. A numerical analysis is performed for the needle-electrode-plane geometry in which the Coulombic force term is included in the Navier-Stokes equation. According to our analysis, electrical charge is generated due to conductivity gradient which is originated from the nonuniform Joule heating of fluid medium. The result of the analysis is compared with experimental result.