As well as powering the tiny robots, which are smaller than a grain of sand, the particles could be used in electronics which are capable of automatically rewiring themselves. The robots could swim through the human body to combat disease or defuse bombs by crawling inside them.

Electrical "Muscles" Could Move Tiny Robots Through Veins

Writing in the journal Nature Materials, study co-author Michael Solomon, a chemical engineer at the University of Michigan, said: “They could work together and go places that have never been possible before.”

Tiny Robots: challenges ahead

Both building and making the robots mobile present huge challenges. “If you imagine a microscale robot in the future, it would need ways to move autonomously and it would need to be able to exert forces, by pushing or pulling on other objects,” he continued.

The scientists first made particles which were the shape of rice grains, but just 0.6 microns wide and 3 microns in length, compared to the average human hair which is around 100 microns wide. One side of each particle was then coated in gold, which meant that the particles attracted each other when placed in salt water to form short chains of overlapping pairs. These chains elongated indefinitely when exposed to alternating electric current.

Tiny Robots: Future possibilities

Researchers have postulated that the fibers could act as muscles by expanding and contracting, and called the degree of control that they have over the chains “exciting.”

“The findings point the way toward a new class of reconfigurable materials made of micron-size particles — materials that can be triggered to morph and change shape in response to changes in environment or on demand,” said researcher Sharon Glotzer.

The fibers generate a force around 1,000 times weaker than human muscle per unit measure, but this could be sufficient for microbots. Further research is required in order to group the chains into bundles, which would allow them to “lift loads, move around, do things that biological muscles do.”

The researchers have predicted that functional microbots powered by this method are a long time away, but electronics which reconfigure themselves are a more eminent possibility.