3D Printing: Researchers Create Magnetic Origami Muscles for Medical Robots

A team of scientists from North Carolina State University (NC State) has produced an ultra-thin magnetic film using 3D printing that can be applied to origami structures. The resulting actuator can be controlled by an external magnetic field and precisely deliver medication within the human body via robots.

The magnetic thin film consists of a rubber-like elastomer embedded with ferromagnetic particles. The NC State researchers created this using a 3D printer, as they describe in the study “3D-Printed Soft Magnetoactive Origami Actuators,” which was published in Advanced Functional Materials. The researchers applied the film to various parts of a structure created using the Japanese folding and cutting art of origami to obtain a tiny robotic actuator.

“Conventional magnetic actuators use small, rigid magnets, like those found on refrigerators, for example. These magnets are attached to the surface of the soft robot and set it in motion,” explains Xiaomeng Fang, assistant professor at the Wilson College of Textiles and co-author of the study. “With this technique, we can print a thin film that we can apply directly to the important parts of the origami robot without significantly reducing its surface area,” she says.

Using a thin magnetic film instead of rigid magnets has another advantage: it significantly reduces the weight of the actuator. However, the researchers encountered a problem: the number of embedded magnetic particles was initially insufficient to adequately control a soft robot via an external magnetic field. The researchers then increased the concentration of particles to achieve higher magnetic force. However, this caused the liquid rubber to turn black and absorb too much of the UV light used to cure the elastomer during 3D printing. Consequently, the rubber could not cure properly. The scientists overcame this issue by adding a heating plate that amplified the UV light and enabled better curing during the printing process.

Robot with Magnetic Origami Muscles

For their medical robot, the researchers used a Miura-Ori fold for the origami muscle. This technique allows a large flat surface to be transformed into a structure with a much smaller surface area through folding. The magnetic film was applied in such a way that the origami structure opens when an external magnetic field is applied. The robot can thus deliver medication to ulcers in the human body and release it there in a targeted and concentrated manner.

The scientists tested the robot in an artificial stomach, a plastic sphere filled with warm water. The robot was maneuvered to the site of an artificial ulcer using the magnetic field. The researchers then fixed the robot's position using externally applied soft magnetic films. It was then magnetically opened, releasing the medication. By fixing the robot, the medication can be released in a controlled manner at the required location over a longer period.

The researchers developed another robot, also based on the Miura-Ori folding technique. It can be made to crawl using an external magnetic field. When a magnetic field is applied, the robot contracts. When the magnetic field is stopped, the robot relaxes again. This creates a step-by-step movement. The robot can thus overcome obstacles up to 7 mm high. The speed and adaptation to different terrain formations are controlled by the applied magnetic field.

“There are many different types of origami structures these muscles can work with, and they can contribute to solving problems in fields ranging from biomedicine to space exploration,” says Fang. “It will be exciting to explore further application possibilities for this technology.”

(olb)