Frequency response of a liquid interface segment actuated using AC EWOD

This work deals with the study of a liquid interface segment as a micromechanical resonator. For free droplet oscillations, reducing the size of the oscillating droplet increases its natural frequency of oscillation. Reducing the size of the droplet for practical applications is, however, limited by issues like evaporation and deposition accuracy. Thus, we investigated local actuation by oscillating a small segment of a liquid interface using AC electrowetting with patterned inplane electrodes. Scaling the “interface length” of an oscillating liquid interface should maximize the resonant frequency. However, we observed overdamped interface oscillations for frequencies 10Hz-1 KHz due to losses and damping mechanisms at small scale dimensions. We also observed contact line patterns pertaining to higher modes upon actuation with higher voltage. This study helps to understand the dynamics of oscillating liquid interface which governs speed and efficiency of liquid switches, liquid lens, lab-on-chip devices and several other applications.