The Coffee Ring Effect

“This never-before-seen footage from a laboratory at the University of Pennsylvania’s Department of Physics and Astronomy shows microscopic particles moving in a drop as it dries. Penn physicists have recently shown that simply changing particle shape can eliminate the ring-shaped stain that is left behind when drops of certain liquids dry. In this video microscopy footage from their experiments, watch as spherical particles get swept to the edges, while oblong particles are distributed consistently.”

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