A technology likened to mini force fields could pave the way to using microrobots (or “microbots”) in manufacturing and medical applications.

Researchers have developed a system for controlling the tiny robots with individual magnetic fields generated by an array of tiny planar coils. Microbots generally move in unison, but being able to control the movement of each robot independently opens the door to performing cooperative manipulation tasks.

Check out the video demonstration below:

(Video courtesy of Purdue University/David Cappelleri.)

"Think of ants. They can independently move, yet all work together to perform tasks such as lifting and moving things,” said David Cappelleri, assistant professor of mechanical engineering at Purdue.

Although the current generation of microbots are two millimeters in diameter, the researchers are aiming to create microbots as small as 250 microns—roughly the size of a dust mite.

Magnetic Fields from Planar Coils

Since batteries are too large for such minuscule robots, the researchers applied magnetic fields to generate forces on the robots, like using mini force fields.

"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? 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?” Cappelleri said.

Past research used fewer coils around the perimeter of the microbots’ workspace, which meant that the generated fields could not control the microbots independently.

"The approach we came up with works at the microscale, and it will be the first one that can give truly independent motion of multiple microrobots in the same workspace because we are able to produce localized fields as opposed to a global field," Cappelleri said.

The coils were made by printing a copper pattern onto a substrate with the same technology that’s used to manufacture printed circuit boards. The coils can be scaled down from their current size to about 4 millimeters. However, a new process is needed to create coils at the microscale.

Microelectromechanical Applications

This new type of microbot can improve the manufacturing process for microelectromechanical systems (MEMS), minuscule machines used in applications as diverse as medicine and homeland security.

"So far people have been good at making MEMS devices containing different components," Cappelleri said. "But a lot of times the components are made from different processes and then have to be assembled to make the final device.”

“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," he added.

Microbots equipped with force sensors might then be used to detect cancer cells in a biopsy by evaluating their stiffness.

One potential obstacle to creating microscale prototypes is the effect of van der Waals forces between molecules at the micron scale. Forces causing “stiction” could interfere with microbot operation.

For more information, check out the research paper published in Micromachines.