Tiny magnetic particles enable new material to bend, twist and grab

A CEM-supported research team from The Ohio State University and the Georgia Institute of Technology has developed a material system that can transform into different shapes through the application of magnetic fields.

The new material, called magnetic shape memory polymers, has the potential to enable a wide range of applications, from biomedical devices to soft robotics. The novel magnetic shape memory polymer composite enables tunable rigidity and has multiple shape manipulation capabilities.

The discovery was reported in the most recent issue of Advanced Materials.

“The new functional soft material enables the development of new advanced material systems that could potentially revolutionize multifunctional robots and machines,” said Renee Zhao, an assistant professor in Mechanical and Aerospace Engineering (MAE). Zhao served as co-principal investigator with H. Jerry Qi, professor of Mechanical Engineering at Georgia Tech.

The new materials integrates fast reversible and reprogrammable actuation, shape locking, and untethered operation for applications in soft robotics, actuators with large gripping force, morphing structures, deformable electronics, especially for designing active and adaptive guidewires, catheters, and stents that could potentially enable the next generation of biomedical devices for minimally invasive operations.

The material is novel in that it achieves multiple shape manipulations in a single material system.

“One of the big challenges in the soft active materials field is how to integrate various shape manipulations into one material system for multifunctional purposes, as many such manipulations are contradictory to each other,” Zhao said. “For example, fast reversible shape change requires that the material can respond to external stimulus rapidly, but shape locking needs the material to have no response or needs to maintain the external stimulus, which requires a constant energy input.”

The magnetic shape memory polymer composite is comprised of an amorphous shape memory polymer matrix of two types of magnetic particles. Researchers were able to soften the matrix and make it pliable by applying a high-frequency, oscillating magnetic field to heat the iron oxide particles and raise the temperature of the actuated shape. Applying a second magnetic field caused rapid and reversible shape change under actuation magnetic fields. Once the shape memory polymers cooled, the shape locked in position.

In a locked state, the strength of the material allowed an actuated gripper to lift up to 1,000 times its own weight. On top of this, the material is adaptive to extreme conditions, allowing application for an array of uses, Zhao said.

“The degree of freedom is limited in conventional robotics,” she said. “With soft materials, that degree of freedom is unlimited.”

Other Ohio State investigators included MAE postdoc Qiji Ze, MAE students Shuai Wu and Rundong Zhang, as well as CEM faculty member Fengyuan Yang, professor of Physics and director of the Center for Exploration of Novel Complex Materials.

The research was supported by Ohio State’s Materials Research Seed Grant Program, funded by the Center for Emergent Materials, an NSF-MRSEC; the Center for Exploration of Novel Complex Materials; and the Institute for Materials Research. Research was also supported by the National Science Foundation (NSF), with an award to Ohio State through NSF’s Materials Research Science and Engineering Centers.