Tiny liquid robots swim around powered by "food" in the water instead of electricity

Researchers have built tiny "liquid robots" that can operate continuously without needing any electricity. Instead, they get their power from chemical processes fueled by "food" they collect from the liquid in which they're swimming. According to the engineers from Berkeley Lab, the 2 millimeter "liquibots" could be used for chemical screening, to discover drugs, or to synthesize new pharmaceuticals by shuttling other chemicals around within a solution. From Berkeley Lab:

Through a series of experiments in Berkeley Lab's Materials Sciences Division, Russell and first author Ganhua Xie, a former postdoctoral researcher at Berkeley Lab who is now a professor at Hunan University in China, learned that "feeding" the liquibots salt makes the liquibots heavier or denser than the liquid solution surrounding them.

Additional experiments by co-investigators Paul Ashby and Brett Helms at Berkeley Lab's Molecular Foundry revealed how the liquibots transport chemicals back and forth.

Because they are denser than the solution, the liquibots – which look like little open sacks, and are just 2 millimeters in diameter – cluster in the middle of the solution where they fill up with select chemicals. This triggers a reaction that generates oxygen bubbles, which like little balloons lift the liquibot up to the surface.

Another reaction pulls the liquibots to the rim of a container, where they "land" and offload their cargo.