Two applications were demonstrated, one being a non-invasive drug delivery system for stomach ulcers and the other a versatile crawling robot capable of traversing obstacles and various terrains. The study also explored the feasibility of directly 3D-printing magnetoactive origami actuators, highlighting the flexibility of the approach for future soft robotic designs.
Background
This research paper focused on developing advanced, wirelessly controlled soft robots by combining origami structures with 3D-printed magnetoactive materials. Previous work in magnet-driven origami actuators often used rigid magnets, which compromised compliance and posed detachment risks. While soft magnetic composites offered a solution, existing 3D printing methods struggled with low magnetic particle content, resulting in weak, thin structures that limited performance.
This study filled these gaps by introducing a customized 3D printing system using a dual-curing mechanism (ultraviolet (UV) light and heat) to process an ink with a high concentration (up to 75 weight percentage (wt.%)) of ferromagnetic particles.
The researchers systematically optimized four formulations of magnetoactive ink (ranging from 33 wt.% to 75 wt.% NdFeB particle loading) before selecting the 75 wt.% composition as the optimal balance between flexibility and magnetic strength. This enabled the fabrication of complex, thick geometries with strong magnetic response and flexibility. The work integrated these materials with various origami patterns to create two demonstrators, one of which was a non-invasive drug delivery robot and the other a versatile crawling robot, showcasing scalable, multifunctional actuator systems.
Fabrication, Testing, and Performance Evaluation
The magnetoactive ink was formulated by mixing neodymium magnet (NdFeB) microparticles with a UV-curable silicone at concentrations up to 75 wt.% using a planetary mixer. A customized direct ink writing system, comprising a robotic arm, pneumatic dispenser, UV laser, and heated collector, was used for printing. The UV laser provided instant surface curing, while the hot plate facilitated full thermal post-curing, enabling the creation of robust, around 0.8 millimeters (mm) thick films. These films were then magnetized and attached to manually folded origami structures.
A rigorous multi-faceted testing regime was employed to characterize the system. The mechanical properties, including Young's modulus, were evaluated via tensile tests. Magnetic performance was assessed through hysteresis loops, contraction force measurements against a permanent magnet, and field strength mapping. The researchers also modeled mechanical stiffness as a function of particle concentration, confirming experimental alignment with theoretical predictions.
Critically, the biocompatibility of the materials was confirmed through in vitro cytotoxicity tests on cardiomyocytes and in vivo subcutaneous implantation in rats, which showed no significant inflammatory response. Finally, the functional performance of the assembled origami actuators was quantified, measuring the contraction ratio of the drug delivery robot and the lifting height and crawling speed of the bio-inspired crawler under various magnetic fields and frequencies.
Results and Discussion
This study presented the development and characterization of high-performance, 3D-printed soft magnetoactive origami actuators. The research first focused on optimizing the magnetoactive ink, finding that a formulation with 75 wt.% NdFeB particles offered the best balance of properties. While the composite's stiffness increased with particle concentration, it remained highly flexible, capable of 360° bending.
This high particle loading resulted in a strong magnetic response, enabling effective remote actuation. Comprehensive in vitro and in vivo tests also confirmed the material's excellent biocompatibility, showing no significant cytotoxicity or inflammatory response. This combination of mechanical strength, magnetic responsiveness, and biocompatibility makes the material well-suited for both biomedical and robotic actuation systems.
Two distinct actuator demonstrations highlight the system's versatility. The first was a non-invasive drug delivery robot for stomach ulcers. Using a Miura-ori origami pattern that can be folded into an ingestible capsule, the device self-deploys in the stomach. It is then magnetically guided to an ulcer site and securely fixed in place for localized treatment, demonstrating high conformity and a large contraction ratio for efficient drug loading. The researchers used a mock-stomach setup to demonstrate the robot’s deployment and navigation, confirming that magnetic forces were sufficient to guide and fix the device securely.
The second is a bio-inspired crawling robot based on a flexible dual Miura-ori structure. This crawler can lift its head in response to a magnetic field, producing a crawling gait. Its speed is tunable via magnetic field strength and frequency, achieving up to 15.2 mm per second (mm/second). The robot successfully demonstrated the ability to traverse diverse terrains, including sand, and climb over obstacles as high as 7 mm. The dual Miura-ori configuration enhanced bendability and motion range compared to conventional origami designs, enabling more dynamic and adaptive movement.
This work established a robust framework for creating wirelessly controlled, multifunctional soft robots with significant potential in biomedical and exploratory applications.
Conclusion
In conclusion, this research highlights the strong potential of 3D-printed, magnetically controlled soft origami robots. By formulating an ink with a high concentration of magnetic particles and introducing a new printing method, the team successfully produced biocompatible films that are both flexible and durable.
The study also touched on the feasibility of directly 3D printing origami-shaped actuators, suggesting a promising path toward scaling up the technology. Looking ahead, future work will explore programmable magnetization, hybrid actuation systems, and more complex origami designs through direct printing, all aimed at improving control and performance.
Journal Reference
Zhang, S., Li, Y., Li, Z., Chedid, N., Zhang, P., Cheng, K., & Fang, X. (2025). 3D-Printed soft Magnetoactive origami actuators. Advanced Functional Materials. DOI:10.1002/adfm.202516404. https://advanced.onlinelibrary.wiley.com/doi/10.1002/adfm.202516404?af=R
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