Microbots Individually Controlled Using 'Mini Force Fields'

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The robots are moved using attractive or repulsive forces and by varying the strength of the electrical current in the coils.

"You can think about using teams of robots to assemble components on a small scale, which we could use for microscale additive manufacturing," Cappelleri said.

Independently controlled microbots working in groups might be useful in building microelectromechanical systems, or MEMS, minuscule machines that could have numerous applications from medicine to homeland security.

"So far people have been good at making MEMS devices containing different components," he said. "But a lot of times the components are made from different processes and then have to be assembled to make the final device. This is very challenging. We can instead assemble them with our robots. And on the biological side we might use them for cell sorting, cell manipulation, characterization and so on. You could think about putting the microcoils on the bottom of a petri dish."

Microbots equipped with probe-like "force sensors" might then be used to detect cancer cells in a biopsy.

"Cancer cells have different stiffness characteristics than non-cancer cells, and in some of our previous work we put force sensors on the end of these robots to figure out which ones are stiffer than others," Cappelleri said.

The coils were made by printing a copper pattern with the same technology used to manufacture printed circuit boards. They can be scaled down from their current size of about 4 millimeters. A new process, however, was needed to create a microscale prototype, he said.

The research is ongoing. The team will attempt to use microscale prototypes to assemble components for MEMS devices. One potential obstacle is the effect of van der Waals forces between molecules that are present on the scale of microns but not on the macroscale of everyday life. The forces might cause "stiction" between tiny components that affect their operation.

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