Leidenfrost Stars

GIF of a transparent droplet vibrating into star-like shapes

Atop a very hot surface, liquids can instantly vaporize, leaving a drop levitating on a layer of its own vapor. These Leidenfrost droplets demonstrate all kinds of interesting behaviors, including self-propulsionexplosion, and star-shaped oscillations, like those above. The oscillation is driven by feedback between the drop and its vapor layer

Interestingly, the drops are capable of sustaining more than one mode of oscillation at once, as seen above. The obvious mode (m=5) corresponds to the 5 star-like points pushing out on the drop. But notice that the drop is also stretching into an oval shape that moves up and down, back and forth. This is the second mode (m=2) present. It moves slower than the m=5 mode, completing a cycle only once for every four cycles the other has. (Image and research credit: J. Bergen et al.)

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