Using magnetism to control soft robots

A team of engineering researchers has made a number of soft robots using magnetic fields to remotely manipulate microparticle chains embedded in the devices.
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The three soft robotic devices in action. Image: NCSU

A team of engineering researchers has made a number of soft robots using magnetic fields to remotely manipulate microparticle chains embedded in the devices.

The group, which included Joe Tracy, an associate professor of materials science and engineering at North Carolina State University, introduced iron microparticles into a liquid polymer mixture and then applied a magnetic field to induce the microparticles to form parallel chains. The mixture was then dried, leaving behind an elastic polymer thin film embedded with the aligned chains of magnetic particles.

“The chains allow us to manipulate the polymer remotely as a soft robot by controlling a magnetic field that affects the chains of magnetic particles,” said Tracy.

He said the chains of iron microparticles respond by aligning themselves and the surrounding polymer in the same direction as the applied magnetic field.

Using this technique, the researchers have created three kinds of soft robots. One device is a cantilever that can lift up to 50 times its own weight. The second device is an accordion-like structure that expands and contracts, mimicking the behavior of muscle. The third device is a tube that is designed to function as a peristaltic pump – a compressed section travels down the length of the tube, much like someone squeezing out the last bit of toothpaste by running their finger along the tube.

“By putting these self-assembling chains into soft robots, we are able to have them perform more complex functions while still retaining relatively simple designs,” said Tracy.

“Possible applications for these devices range from remotely triggered pumps for drug delivery to the development of remotely deployable structures.”

He says the next step is to improve both the control and the power of these devices. They have developed a metric for assessing the performance of magnetic lifters, such as the cantilever device, by measuring the amount of weight being lifted and taking into account both the mass of particles in the lifter and the strength of the magnetic field being applied.

[The three soft robotic devices in action. Image: NCSU]