Bouncing an oil-coated water droplet creates tiny emulsion
Scientists in Belgium have uncovered a new way to shake things up. Violent bouncing of a water droplet coated with oil causes the oil layer to move inside and fracture into many oily globs. In a paper published in the December Chaos, researchers at the University of Liège in Belgium call this microemulsion of oil and water the mayonnaise droplet.
From earlier experiments, researchers knew that oily droplets bounce several times on a bed of oil before merging with the oil base. But Denis Terwagne and colleagues wanted to know what would happen to an oil-coated water droplet if the bouncing was prolonged. To find out, the team constructed a moving base that would quickly raise and lower the oil bed, similar to using a horizontal Ping-Pong paddle to keep a ball bouncing.