Dribbling Droplets

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Ethanol droplets on a hot copper plate bounce under the influence of electrostatic forces from a charged rod. The temperature of the plate is high enough that the droplet is supported by a thin vapor film, which is what keeps it from wetting the plate.  Ethanol does not have the strong polarity that water does, but the hydroxyl group on one end does make it susceptible to the electrostatic charge built up on the teflon rod.  As a result, the droplets oscillate under electrostatic and gravitational forces, resulting in a dribbling effect. (Video credit: S. Wildeman et al.)

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