Non-axisymmetric oscillations of droplets in electrowetting-on-dielectric

Water droplets actuated by alternating fields mostly show axisymmetric modes. Under certain actuation conditions, non-axisymmetric resonance modes grow at the cost of axisymmetric modes. Using high speed imaging, we studied the growth dynamics of these non-axisymmetric modes of water droplets actuated by AC electrowetting-on-dielectric (EWOD). It was observed that at certain frequencies the non-axisymmetric modes grew with increasing actuation voltage. After a critical voltage, the non-axisymmetric modes were observed to become dominant. These observations agree with a parametric oscillator. A theoretical model explaining the observed responses has been developed.