Dynamics of electrically stressed water drops on insulating surfaces

A single drop on an insulating surface stressed by an electric field parallel to it has been studied for a range of drop volumes for different insulating materials, under both DC and AC stress. The results show that on hydrophobic surfaces, the electrohydrodynamic effects are quantitatively the same as for a free drop. The less hydrophobic the surface, the larger is the deviation from free drop behavior. For DC, the drop elongation occurs somewhat stepwise due to contact angle hysteresis. For AC, the elongation is smooth and flashover due to instability occurs at a lower field strength. When the AC frequency is increased above the power frequency, the flashover voltage increases. Vibration modes for drops on hydrophobic surfaces are very similar to free drop modes.<>