Doi: 10.1038/s41586-025-09706-4
Please refer to: https://www.nature.com/articles/s41586-025-09706-4.
A team of PolyU researchers reported soft fibres and fibre assemblies that can quickly and reversibly change their form and mechanical characteristics in response to a safe and low magnetic field. These programmable textiles have potential applications in soft robotics, electromagnetic devices and wearable technologies.
Magnetorheological (MR) materials like fluids or polymer composites can change shape or mechanical properties quickly when exposed to a magnetic field. Typically, magnetic particles suspended in a fluid or polymer form fibre-like structures under a magnetic field, altering their properties. However, issues such as sedimentation and aggregation in fluid-based MR materials lead to instability and inconsistent performance. While MR polymer composites solve some stability problems, they often hinder responsiveness due to the restrictive polymer matrix and ineffective magnetic micro-particles.
To address these issues, the research team designed fibrous MR materials. They created soft-magnetic polymer composite fibres, 57 microns in diameter, that can be manipulated with low-strength, human-safe magnetic fields. This was achieved by uniformly distributing carbonyl-iron particles within a low-density polyethylene matrix, which allows for magnetic alignment and prevents sedimentation.
Using these MR fibres, the team constructed various fibrous architectures, including yarns and multi-layer fabrics, without relying on magnetically inactive bonding matrices. This innovative system enables a scalable approach from fibres to large-area fabrics with directional deformation control. Unlike traditional responsive materials that react to scalar stimuli, these MR textiles respond to 'vectorial' magnetic fields.
The researchers established magneto-mechanical models for the textile structures and determined key parameters for customizing composite formulations and yarn structures, combining textile structural design with the magnetics of composite materials. The resulting MR yarns exhibit unique bending and stiffening modes based on the magnetic field's direction, allowing for programmable movements and 30-times changes in stiffness in various applications. The team also developed program-controlled devices from these MR fabrics, including an active ventilation fabric for moisture control, a flexible gripper for handling different objects, and a remote-controlled haptic glove that simulates surface of various textures and hardness.
This breakthrough extends MR technology into fibrous forms, combining tunable stiffness with versatile deformation while incorporating lightweight, flexible, and breathable textile properties—capabilities do not present in traditional MR systems.
The strategies employed could also apply to hard-magnetic fibrous materials, transforming standard rigid magnetic devices into soft, flexible alternatives. Such advancements could pave the way for a new generation of soft robotics, electro-mechanical devices, and wearable systems.
The team's low-magnetic-field control technology will be crucial for human-centered applications, with plans for both remote magnetic manipulation and the integration of textile-based electromagnets within fabrics.
The progress in the smart MR fibrous assemblies is the result of over 30 years of research led by Prof. Tao at The Hong Kong Polytechnic University. This extensive study has explored a wide array of applications, from sensors to actuators and systems. The programmable MR fibre assemblies were developed through collaborative efforts from various disciplines aimed at creating future wearable devices that mimic human sensory capabilities, as a part of a Theme-based Research Program funded by Research Grants Council of Hong Kong.
Authorship:
Pu Junhong: Research Assistant Professor, School of Fashion and Textiles (SFT), Member of the Research Institute of Intelligent Wearable Systems (RI-IWEAR), The Hong Kong Polytechnic University (PolyU).
Li Haiqiong: Research Assistant, SFT, PolyU
Liu Jin: PhD graduate, SFT, PolyU
Li Ke: PhD student, SFT, PolyU
Tao Xiaoming: Director of RI-IWEAR, Chair Professor of Textile Technology, SFT, PolyU
