Soft Material Developed With Magnetic Response

Coil made with magnetic shape polymer material (Allison Carter, Georgia Tech)

11 Dec. 2019. Researchers created a new soft polymer plastic with magnetic properties that can be programmed to change shape and recall previous shapes. The material — with applications in robotics, electronics, and medical devices — is described in the 8 December issue of the journal Advanced Materials (paid subscription required).

A team from Georgia Institute of Technology in Atlanta and Ohio State University in Columbus developed the magnetic shape memory polymer to provide a combination of desirable properties in a single composite material. Engineers and materials scientists from the labs of Jerry Qi at Georgia Tech and Ohio State’s Ruike Zhao are seeking a flexible and pliable substance that can be programmed to change shape quickly, yet revert to its previous shape if needed.

The Georgia Tech-Ohio State team started with shape memory polymers, plastic materials that change their shape in response to heat, light, or other stimuli, yet can be restored to their previous shape. Shape memory polymers are used in a range of applications including smart fabrics, electronics, mobile phones, and implanted medical devices. Science & Enterprise reported in September 2018 on shape memory materials housing electronics to provide robotics functions to inanimate objects.

In their paper, Qi, Zhao, and colleagues add magnetic particles to shape memory polymers to provide a magnetic response for producing heat to change the material’s shape, as well as programming ability, which are restricted in many current robotic materials. “The degree of freedom is limited in conventional robotics,” says Zhao in a Georgia Tech statement. “With soft materials, that degree of freedom is unlimited.”

To provide these features, neodymium iron boron, a commercially-available magnetic material, and iron oxide particles are distributed through the polymer. When exposed to a magnetic field, the magnetic particles begin to heat, and from that heat, the polymer becomes soft and pliable, allowing it to change shape. After stopping the magnetic field, the polymer cools and returns to its hardened form.

In bench tests, the researchers shaped the polymer into a coil, with the material expanding and contracting. The team stretched and retracted the coil to simulate an antenna changing frequencies, in response to various magnetic fields. The researchers also added a second magnetic field to operate a robotic gripper. The first magnetic field softened the polymer material in a T-shaped mold, to make it pliable. The second magnetic field then controlled the opening and closing of the gripper.

“We envision,” says Qi, “this material being useful for situations where a robotic arm would need to lift a very delicate object without damaging it, such as in the food industry or for chemical or biomedical applications.” The researchers note that the material changes shapes in just a few seconds, and when the material cools, the gripper can lift items up to 1,000 times its own weight.

“This is the first material,” adds Qi, “that combines the strengths of all of these individual components into a single system capable of rapid and reprogrammable shape changes that are lockable and reversible.” This Georgia Tech video demonstrates a few applications of the material.

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