Typhoon Inside a Drop
This image shows the trajectories of many tiny tracer particles moving inside a decane droplet (diameter 100 micrometer). A total of 1000 images taken over 2 min are stacked together.
The motion visualized here is induced by the external butanol gradient, which in turn creates interfacial gradient along the droplet surface. Due to the symmetry of droplet shape, the motion is formed as rotation around a stagnant point in each half of the droplet.