Microbots Individually Controlled Using 'Mini Force Fields'

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Researchers are using a technology likened to "mini force fields" to independently control individual microrobots operating within groups, an advance aimed at using the tiny machines in areas including manufacturing and medicine.

Until now it was only possible to control groups of microbots to move generally in unison, said David Cappelleri, an assistant professor of mechanical engineering at Purdue University.

"The reason we want independent movement of each robot is so they can do cooperative manipulation tasks," he said. "Think of ants. They can independently move, yet all work together to perform tasks such as lifting and moving things. We want to be able to control them individually so we can have some robots here doing one thing, and some robots there doing something else at the same time."

Findings are detailed in a research paper appearing this month in the journal Micromachines.  Postdoctoral research associates Sagar Chowdhury and Wuming Jing, and Cappelleri authored the paper.

The team developed a system for controlling the robots with individual magnetic fields from an array of tiny planar coils.

"The robots are too small to put batteries on them, so they can't have onboard power," Cappelleri said. "You need to use an external way to power them. We use magnetic fields to generate forces on the robots. It's like using mini force fields."

The research is revealing precisely how to control the robots individually.

"We need to know, if a robot is here and it needs to go there, how much force needs to be applied to the robot to get it from point A to point B?" Cappelleri said. "Once you figure out what that force has to be, then we say, what kind of magnetic field strength do we need to generate that force?"

The microbots are magnetic disks that slide across a surface. While the versions studied are around 2 millimeters in diameter – about twice the size of a pinhead - researches aim to create microbots that are around 250 microns in diameter, or roughly the size of a dust mite.

In previously developed systems the microbots were controlled using fewer coils located around the perimeter of the "workspace" containing the tiny machines. However, this "global" field is not fine enough to control individual microrobots independently.

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