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Dancing Droplets Reveal Physics at Work
from Science News
Throw water into a hot pan, and it will sizzle so fast that the drops actually levitate across the surface. Physicists have now taken this phenomenon, called the Leidenfrost effect, a step further: Using magnets, the scientists directed droplets of liquid oxygen to speed up, slow down and change course as they scoot across a sheet of glass.
Magnetic fields force the tiny blobs to travel in a mesmerizing dance, says David Quéré, a physicist at ESPCI Paris Institute of Technology in France. He and his colleagues describe the work in an upcoming Physical Review E.
Leidenfrost drops form when a drop hits a surface much hotter than the liquid's boiling temperature. The liquid evaporates so quickly that the droplet starts to float on its own vapor, cushioned from below. This insulating layer also reduces friction between the droplet and the surface. Given a push, a droplet 1 millimeter across can slide for several meters before finally slowing down and stopping.