Researchers Pop the Boundaries on Bubbles

Harvard University researchers have developed “armored” bubbles capable of resisting their natural tendency to become spheres, thus allowing them to be formed into a variety of unusual shapes.

The team, led by engineering research associate Anand Bala Subramaniam, began by adhering the armor -- a single chain of metallic or plastic particles -- to the surface of gas bubbles.

Natural forces compel liquids to reduce their exposed surface to the smallest possible area -- a sphere. But the chain of particles, depending on its placement, restricted the bubbles’ shape.

The particle chains were flexible enough to allow the researchers to mold the bubbles into the shapes of sausages, peapods, disks, doughnuts and others items, said Bala Subramaniam, who reported his results in the current issue of the journal Nature.

Because the armored bubbles, which ranged from 1 micron to 1 millimeter in size, could support unequal stresses, Bala Subramaniam’s team deemed them solids rather than liquids.

But unlike other solids, the bubbles were able to be extensively remodeled “like silly putty that can be hardened and softened at will,” he said.

Bala Subramaniam said custom-shaped bubbles could be used in the future to create new textures in such products as ice cream and shaving foam. Nonspherical bubbles could also be used to create vessels for carrying minute doses of drugs into irregularly shaped blood capillaries.