A crawling robot created with the Miura-Ori origami pattern. The dark areas are covered in a thin magnetic rubber film which allows the robot to move.
A new 3-D printing technique can create paper-thin “magnetic muscles,” which can be applied to origami structures to make them move.
By infusing rubber-like elastomers with materials called ferromagnetic particles, researchers at North Carolina State University 3-D printed a thin magnetic film which can be applied to origami structures. When exposed to magnetism, the films acted as actuators which caused the system to move, without interfering with the origami structure’s motion.
This type of soft magnet is unique in how little space it takes up, said Xiaomeng Fang, assistant professor in the Wilson College of Textiles and lead author of a paper on the technique.
“Traditionally, magnetic actuators use the kinds of small rigid magnets you might put on your refrigerator. You place those magnets on the surface of the soft robot, and they would make it move,” she said. “With this technique, we can print a thin film which we can place directly onto the important parts of the origami robot without reducing its surface area much.”
Scientists designed their primary robot to deliver medicine to ulcers inside the human body, using an origami pattern called Miura-Ori. The technique allows a large flat surface to fold into a much smaller area. The magnetic “muscles” are attached to facets of the origami – when exposed to a magnetic field, they help the origami open up and navigate to the ulcer location. The Miura-Ori design is well-suited to administering medicine, Fang said, because it can be ingested as a small object and then open to deliver medicine with its entire surface area.
Researchers tested the robot using a mock stomach made of a plastic sphere filled with warm water. Guiding the robot through the stomach using external magnetism, researchers successfully maneuvered it to an ulcer site, deployed it into its unfolded state, and secured it in place by externally attached soft magnetic films. This setup enabled controlled and steady drug release over time, for a safe and non-invasive procedure which allows patients to carry out daily activities as normal.
Previous attempts to use ferromagnetic particles have struggled to generate enough force to move robots, Fang said, because they were not able to pack enough particles into the rubber solution. Adding a large quantity of particles turns the liquid rubber black, which absorbs the UV used to solidify the solution and keeps it from curing properly. Thermal energy can also help solidify the rubber, so researchers added a hot plate underneath the collecting plate to augment their UV light.
“Adding the hot plate meant that we could use a much higher concentration of ferromagnetic particles than usual, which was the real breakthrough,” Fang said. “The more particles you are able to use, the more magnetic force you are able to generate.”
Using a different Miura-Ori origami pattern, researchers also created a second robot designed to crawl forward. When placed in a magnetic field, muscles placed at specific areas of the robot cause it to contract, with the front section raising up and the rear drawing in closer. When the field is turned off, the motion of returning to its original position pushes the robot forward – a single “step.” This crawling origami robot is capable of traversing obstacles up to 7 millimeters high with speed adjustable via magnetic field strength and frequency, and adapting to diverse terrains, including sand.
Taken together, these two robots demonstrate the significant potential of soft magnetic actuators and origami structures in robotics, Fang said.
“There are many diverse types of origami structures that these muscles can work with, and they can help solve problems in fields anywhere from biomedicine to space exploration,” Fang said. “It will be exciting to continue to explore more applications for this technology.”
The paper, “3D-Printed Soft Magnetoactive Origami Actuators,” is published in Advanced Functional Materials. Co-authors include Sen Zhang, Yuan Li, Zimeng Li, Nabil Chedid, Peiqi Zhang and Ke Cheng of NC State University.
Note to editors: The abstract of the paper follows.
3D-Printed Soft Magnetoactive Origami Actuators
Authors: Xiaomeng Fang, Sen Zhang, Yuan Li, Zimeng Li, Nabil Chedid, Peiqi Zhang and Ke Cheng, NC State University
Published: Sept. 12 in Advanced Functional Materials
DOI: 10.1002/adfm.202516404
Abstract: Soft magnetoactive material-driven origami actuators, controlled wirelessly by external magnetic fields, combine the folding capabilities of origami with the compliance of soft materials. However, research in optimizing magnet placement and field direction for enhanced actuation remains limited. This study presents 3D printed soft magnetoactive materials integrated into various origami structures with different film placements, enabling applications in non-invasive drug delivery and crawling robotics. The printing ink, containing up to 75 wt.% ferromagnetic particles and UV-curable elastomers, is processed using a customized 3D printing system with dual curing mechanism-UV light and heated collecting platform, allowing instantaneous consolidation of complex 3D geometries with considerable height and thickness. The resulting films exhibit strong magnetic response, flexibility, and programmable polarity, supporting untethered actuation with substantial force. Two origami actuators are developed: a non-invasive drug delivery targeting stomach ulcer treatment, demonstrating a high folding-to-deployment ratio, precise guidance and secure fixation to the ulcer site, good biocompatibility; and a robotic crawler capable of traversing obstacles up to 7 mm high with speed adjustable via magnetic field strength and frequency, and adapting to diverse terrains, including sand. This work highlights the potential of combining soft magnetoactive materials and origami for scalable, wireless, and multifunctional actuator systems.
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