Bubble removal by electric and acoustic actuation for heat transfer enhancement

This paper presents a technology for the removal of bubbles using the two mechanisms of electric and acoustic actuation. In this study, dielectrowetting was used to separate bubbles from the surface of a substrate, while acoustic actuation was used to transfer and eliminate separated bubbles by acoustically exciting them. In addition, the electrical signals of various voltages and frequencies were applied to patterned electrodes fabricated through the standard microfabrication processes in order to investigate the dynamic behaviors of the dielectrowetting driven bubbles, such as the contact angles of the bubbles and their separated distances from the surface. Furthermore, a high-speed camera was used to measure the velocities of single bubbles separated from the surface through acoustic excitation at various frequencies in order to identify the velocity and efficiency at which bubbles were transported and removed by acoustic excitation. To test the feasibility of removing multiple bubbles of various volumes, an experiment was carried out in which the proposed dielectrowetting and acoustic actuation were used to separate bubbles of different volumes from the surface simultaneously and then remove them. The experiment revealed that multiple bubbles of various volumes could be removed all at once in a second. The proposed method of removing bubbles can be used in a variety of industrial applications that require the transfer of large quantities of heat.