Researchers at the University of Michigan have demonstrated that oblong gold plated particles will form chains and respond to an alternating electric current by expanding by roughly 36 percent. This means that the particle chains expand and contract predictably as the current switches rapidly on and off.

This expansion and contraction is similar to the behavior of muscles. The human heart, for example, pumps blood because the muscles that surround the heart expand and contract rhythmically.

At the moment this research is largely theoretical. The flexing chains are not robots, nor are they being used in robotics yet. However, it creates the potential for a variety of nanotechnology applications.

“What’s really important in the field of nanotechnology right now is not just assembling into structures, but assembling into structures that can change or shape-shift,” said Sharon Glotzer in a statement. Glotzer is a Professor of chemical engineering whose team created computer simulations to demonstrate the movement of the particle chains.

The team started with particles about a hundred the width of a human hair. These particles were stretched into oblong shapes and one side of the particle was plated with gold. The plated sides of the football shaped particles demonstrated a slight attraction to one another in salt water. The more salt that was present in the water, the greater the attraction became.

On their own, in the salt water, the particles would form chains of 50-60 particles. However, when an electric current was added to the water, the chains would expand indefinitely. This expansion, or stretching creates the possibility of moving microbots.

“The particles are like children in a playground. They do interesting things on their own, but it takes a headmaster to make them do interesting things together,” said Aayush Shah, a doctoral student in chemical engineering.

The force generated by the expansion is small, at 1,000 times less than a typical human muscle. For micro-robotics that tiny amount of motion may be enough.

“We want them to work like little muscles. You could imagine many of these fibers lining up with the field and producing locomotion by expanding and contracting,” said Glotzer.

According to the researchers if the chains of particles can be trained to swarm or work together they could replicated the function of stronger, biological muscles. More immediately, the chains could allow electronic devices to rewire themselves.

“These chains are essentially wires, so you could assemble them into a circuit for reconfigurable electronics,” said Michael Solomon, a professor of chemical engineering.

The team is proceeding with its research in an effort to better understand the phenomenon they’ve discovered.

“We don’t fully understand why the chains extend, but we have some ideas,” said Benjamin Schultz, a graduate student in Glotzer’s group.