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Researchers Successfully Manipulate Soft Robots Using Magnetic Fields

Researchers at NC State University have created several soft robot devices that make use of a fundamental advance in controlling soft robots. The new technique uses magnetic fields to remotely manipulate microparticle chains embedded in soft polymers. (Credit: Joe Tracy)

Engineering researchers have made breakthrough advancement in manipulating ‘soft robots’ using magnetic fields to remotely control microparticle chains fixed in soft robotic devices. The team has already built several devices that apply the new method.

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

Joe Tracy, Associate Professor, Materials Science and Engineering, North Carolina State University

The new method builds on earlier research in the domain of self-assembling, magnetically actuated composites by Tracy and Orlin Velev, the INVISTA Professor of Chemical and Biomolecular Engineering at NC State.

For this research, the team added iron microparticles into a liquid polymer mixture and then used a magnetic field to cause the microparticles to develop parallel chains. When the mixture was dried, it left 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,” Tracy says.

Specifically, the magnetic field’s direction and strength can be varied. The chains of iron microparticles react by aligning themselves and the adjacent polymer in the same direction as the applied magnetic field.

Using this method, the research team has built three kinds of soft robots. One is a cantilever that is capable of lifting up to 50 times its own weight. The second robot is an accordion-like structure that can expand and contract, imitating the action of muscle. The third robotic device is a tube that is engineered to function as a peristaltic pump – a compressed section moves down the length of the tube, similar to someone squeezing out the last bit of toothpaste by moving their finger along the length of the tube.

We’re now working to improve both the control and the power of these devices, to advance the potential of soft robotics.

Joe Tracy, Associate Professor, Materials Science and Engineering, North Carolina State University

The researchers have also formulated a metric for evaluating the performance of magnetic lifters, such as the cantilever device.

We do this 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. We think this is a useful tool for researchers in this area who want to find an empirical way to compare the performance of different devices.

Ben Evans, Associate Professor of Physics, Elon University

The research paper titled “Chained Iron Microparticles for Directionally Controlled Actuation of Soft Robots,” is published in the ACS Applied Materials & Interfaces journal. The paper’s lead author is Marissa Schmauch, an undergraduate at the University of Tulsa who worked on the project while at NC State as part of the National Science Foundation’s Research Experiences for Undergraduates program. The research paper was co-authored by Velev and former NC State Ph.D. student Sumeet Mishra.

Schmauch’s participation was funded by the Research Triangle MRSEC, NSF grant number DMR-1121107. The research was also supported by NSF grant number DMR-1056653.

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