Kyushu University: 4D Printing Magnetic Soft Actuators

Japanese researchers from Kyushu University have created a 4D printer for magnetic soft actuators, outlining their research in the recently published paper ‘Bio-Mimic Motion of 3D-Printed Gel Structures Dispersed with Magnetic Particles.’ Authors Hayato Shinoda, Seiji Azukizawa, Kazuki Maeda, and Fujio Tsumori designed new hardware for making 3D prints as well as 4D printing materials. The result of their work arrives in the form of actuators able to function as biomimetic examples with the potential to deform via a magnetic field—as magnetic anisotropy is “applied at each portion of printed structures.”

Each particle is magnetized before printing, causing it to rotate during curing.

“At the first step, a magnetic field is applied to set magnetic anisotropy to the curing part, and another magnetic field is applied for the next portion. After printing, the structure can work as an actuator under a magnetic field; aligned magnetic particles in each portion causes the rotational moment to be along with the magnetic flux line,” state the researchers.

There were two different types of biomimetic structures created: a worm-like structure, and an array of artificial cilia. Inspired by nature as scientists so often are, the researchers fabricated actuators able to contract continuously and move forward in a wave-like formation, then deforming. The researchers state that it could be demonstrated as a simple beam structure, separated into two areas.

“The worm structure was set in a narrow gap between two walls, and the actuator could move forward in a narrow gap like a worm with propagating wave deformation in the body,” explained the researchers.

Flow of the present fabrication and actuation system.

Schematic illustration of 3-dimensional printing system using a gel material dispersed with magnetic powder. There is a permanent magnet below the resin bath to set an applied magnetic field at the building portion.

The artificial cilia samples were created to imitate flowing “hair-like organisms,” exhibiting a metachronal wave. The research team created four kinds of cilium with varying anisotropy.

“The printed cilia stood on the side wall of a rectangular block, which was also printed at the same time. The cilia and the block were set in a water pool, and rotating magnetic field was applied by a permanent magnet located outside of the pool,” stated the researchers.

Printed artificial cilia with a metachronal wave.

To date, the team had not yet tested the structures for mechanical strength or other properties, but they were able to estimate residual flux density at about 3 mT, with magnetic flux density of 30 mass% ferrite material estimated at about 25 mT. Stating that finite element analysis would be a “powerful tool,” the researchers explained that it would also be helpful for future studies to use a range of boundary conditions.

“The present system is useful to mimic motion of natural creatures,” concluded the authors. “We also showed some formulations to express deformation of the worm-like structure. The computational designing system would be a powerful tool to design bio-mimic motions in the nature. Implementation of FEA system is our future work.”

If 3D printing offers a multitude of innovations to the world, seemingly almost magical, 4D printing takes that one level further. With materials that morph and adapt to their environment, designers and engineers have created reconfigurable metamaterials, cellulose-based ink, and varying approaches with multiple materials. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

Overview of the developed 3D printer. UV laser was scanned by a galvano scanner on the surface of resin pool. A permanent magnet was set under the pool to apply a magnetic field. The angle of the magnetic field could be changed by rotating the angle of the magnet.