When a water drop sticks to a vibrating plate, there is a phase shift between the plate and the drop. The phase shift depends on the drop size and the exciting vibration frequency. The tunable phase shift covers the whole range from 0 to \pi. When two nearby drops of different sizes are driven by a plate vibration at a carefully chosen frequency, there is a maximum phase shift between the two. They oscillate in opposite directions. We show in the video how the mechanism promotes drops merging at this frequency. The mechanism is easily understood thanks to a classical damped spring-mass model. The finding has high application perspectives in dew harvesting, condensation enhancement, among many others.
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