UNIST Professors Kim Ji-yoon and Seoul National University Professor Kwon Min-sang Develop 'Magnetic Smart Material'
Applied to Biomedical Engineering and Soft Robot Development ... Published in 'Nano Letters'
[Asia Economy Yeongnam Reporting Headquarters Reporter Kim Yong-woo] A ‘smart material’ that responds to magnetic fields and moves on its own has been developed.
The research team led by Professor Kim Ji-yoon of the Department of Materials Science and Engineering at Ulsan National Institute of Science and Technology (UNIST), in collaboration with Professor Kwon Min-sang’s team from the Department of Materials Science and Engineering at Seoul National University, announced on the 3rd that they have developed a magnetic smart material capable of changing its magnetization pattern.
The research team stated that this development of the ‘magnetic smart material’ allows for more diverse shapes. The shape in which the magnetic smart material moves is determined by the internal ‘magnetization pattern’ of the material, and this is possible because a technology to easily erase and rewrite the magnetization pattern has been developed.
It is generally difficult to change the magnetization pattern formed inside the material during the manufacturing process of magnetic smart materials, but the research team overcame this limitation by using a substance that melts at a low temperature.
Magnetic smart materials are known to move through the interaction between the pre-input magnetization pattern inside and an external magnetic field. This is similar to using the attractive or repulsive forces that occur when bringing one magnet close to another.
The magnetization pattern is a ‘blueprint’ that determines the strength of the magnetic force and the direction of the N-S poles. Depending on the magnetization pattern, the magnetic smart material bends or folds in a specific direction.
However, once the magnetization pattern is fixed during the material manufacturing process, it is not easy to change it. Because of this, despite the advantages of being remotely controllable and quickly responsive to external stimuli, magnetic smart materials have not been widely used.
The joint research team solved this problem by using a material whose state changes depending on temperature. The developed material has a structure in which micrometer-sized particles (magnetic microspheres) composed of a mixture of ‘magnetic particles’ (magnetic material) and a ‘phase-change material’ (PEG) are embedded in a polymer matrix.
Because PEG is a phase-change material that transitions from solid to liquid, it allows the magnetization pattern to be changed repeatedly. Just as beads in ice are firmly fixed but can move freely in water, the magnetic particles can be newly programmed with a magnetization pattern using an external magnetic field due to the phase-change material becoming liquid.
On the other hand, when the temperature drops to room temperature, the phase-change material solidifies, physically immobilizing the magnetic particles and fixing the magnetization pattern.
Hyunseo Song, first author and integrated MS-PhD course researcher at UNIST’s Department of Materials Science and Engineering, explained, “The solid-liquid phase change of PEG is a ‘reversible reaction,’ so simply repeating this process allows the magnetization pattern of the soft composite material to be easily redesigned (reprogrammed) as desired.”
The research team also created a magnetic soft actuator capable of ‘self paper folding’ using the developed composite material. They redesigned the magnetization pattern of the actuator in actual operating environments and exposed it to magnetic fields to realize various complex three-dimensional shapes.
Because of the reversible reaction, the material maintains its performance even when new magnetization patterns are repeatedly input into the same actuator.
Professor Kim Ji-yoon of UNIST said, “Unlike previous studies, this material was developed to easily redesign the magnetization pattern without changing the inherent properties of the magnetic particles or polymer matrix, which is significant. The developed material also has flexibility, so it is expected to be utilized in various fields requiring variable-structure smart materials such as biomedical engineering, flexible electronic devices, and soft robotics.”
This research was published on July 8 in ‘Nano Letters,’ the world’s leading journal in the field of nanotechnology. The research was supported by the National Research Foundation of Korea (NRF) and the Korea Evaluation Institute of Industrial Technology.
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