They look like tiny tadpoles or perhaps the larvae of some insect as they zip through the liquid in their dish, but they are neither. This swarm of energetic specks is comprised not of little critters, but of droplets of liquid metal.
Each shiny little dot is a simple self-powered motor made of a liquid aluminum alloy. Bubbles of hydrogen gas that come off the back end of these miniature motors propels them forward, researchers report in a paper published in the journal Science Bulletin.
"The present finding is rather unconventional and is expected to be important in a variety of areas such as designing micro-robots, tiny soft machine or motors, drug delivery, microfluidics and can even be directly developed as injectable tiny medical care devices in the near future," senior study author Jing Liu told Tech Times.
The tiny motors move around very quickly, so the researchers had to use a high-speed camera to capture this video of them. It's shot at 100 frames per second, whereas a typical movie, for reference, is shot at just 24 frames per second.
The hydrogen bubbles are the product of a chemical reaction between the aluminum alloy of the motor and the alkaline solution in which they're swimming This new method of producing hydrogen could facilitate the introduction of more environmentally friendly hydrogen-powered technologies such as the hydrogen-powered cars that Toyota has already begun to develop.
"It has particular significance for current society in the sense of providing a green way for realizing hydrogen energy," Liu said.
The findings also have implications for a well-known physical phenomenon known as Brownian motion, which describes the patterns of motion of molecules as they bounce off one another. These small but macroscopic motors move in a similar way, the researchers found.
"However, unlike the existing phenomena, where the particle motions were caused by collisions from the surrounding molecules, the current random liquid metal motions are internally enabled and self-powered," Liu said.
These liquid metal minimotors won't be powering your car anytime soon, but researchers plan to explore this potential application in future studies.