Electrowetting-on-dielectric induced bubble dynamics and surface waves

This paper presents electrowetting-on-dielectric (EWOD) induced bubble dynamics (i.e., oscillation, escape, and detachment) along with surface waves. When voltage was applied to the electrowetting system, the contact angle declined as the absolute value of voltage increased. Bubble oscillation was demonstrated under sine, triangle, and square waves. A gradual change in contact angle was observed in the sine and triangle waves, whereas the square wave exhibited a relatively small and constant contact angle most of the time. Under the same applied peak voltage, the sine wave showed a weaker electrowetting effect, the triangle wave was moderate, and the square wave demonstrated a stronger effect. When the electrode wire was right above the bubble, the bubble oscillated at its initial position. When the electrode wire was placed on one side, electrowetting repelled the bubble from its initial position. The electrowetting effect on the lateral wall was studied when a sine wave with 70V peak voltage and 1Hz frequency was applied to the system. A surface wave generated via motion of the three-phase contact point was detected. Bubble detachment due to bubble oscillation and surface wave perturbation was captured by a high-speed camera. The study presented in this paper holds great significance for actively controlling bubble dynamics and improving the operating efficiency in fluid dynamic and heat transfer systems.