Microscopic robots, or microbots, could someday help fight diseases, crawl into and diffuse a bomb, and also play a crucial role in evacuation efforts. Building these tiny robots and making them mobile are, however, currently hampered by major challenges.

The nanobots need to move independently and would need to exert force by pushing or pulling objects if they are to work as imagined for a microscale robot that could be a game changer in a number of fields and industries in the future.

In a bid to find a way to power these microbots, chemical engineer Michael Solomon from the University of Michigan at Ann Arbor and colleagues proposed using self-assembling chains of microscopic particles as the electrically activated muscles of these tiny bots.

For their study published in the journal Nature Materials on Nov. 10, Solomon and colleagues stretched spherical particles made of a combination of polystyrene in a machine until they became oblong-shaped, measuring about 0.6 microns wide and 3 microns long then coated one side of each of these particles with gold.

The gilded sides of the Janus particles, so named because they have two different faces, attracted one another in salty water. The researchers said that the attraction becomes stronger when there is more salt in the water.

The particles then independently formed overlapping chains of about 50 to 60 particles per chain on average but when exposed to alternating electric current, the chains appeared to add new particles indefinitely. The researchers reported that the process resulted in the chains extending by about 36 percent.

"Actuation of the fibres occurs through a sliding mechanism that permits the rapid and reversible elongation and contraction of the Janus-ellipsoid chains by ~36% and that on long timescales leads to the generation of long, uniform self-assembled fibers," the researchers reported.

Study co-author Sharon Glotzer, also from the University of Michigan at Ann Arbor, said that expanding and contracting the fibers could make them work like little muscles and, although the fibers produce force that is about 1000 times weaker compared with human muscle tissue per unit area, the researchers said that the force is enough for the microbots.

"If we can get the chains to swarm together, we can get them to lift loads, move around, do things that biological muscles do," Solomon said. "These chains are essentially wires, so you could assemble them into a circuit for reconfigurable electronics."

Watch the video on how self-assembling particle chains could power futuristic microbots: