On November 5, Professor Li Liang's team from the National Pulsed High Magnetic Field Science Center and the School of Electrical and Electronic Engineering at Huazhong University of Science and Technology made significant progress in the field of magnetically controlled soft actuators. They overcame the bottleneck problem of the "strong correlation between deformation amplitude and magnetic field strength" in traditional actuators, achieving large deformation control driven by low magnetic fields.

The research results were published in Nature Communications under the title "Magnetoactive bistable soft actuators for programmable large shape transformations at low magnetic fields". 

Research Background

Magnetically controlled soft actuators, with advantages such as remote, tether-free control and programmable deformation capabilities, show great application potential in fields like soft robotics and biomedical applications. However, traditional actuators are limited by the deformation mechanism involving continuous competition between magnetic torque and elastic restoring torque, leading to a strong correlation between deformation amplitude and magnetic field strength. This results in two inherent limitations: "high-field dependence" and "state instability". Achieving large deformations relies on continuous excitation by high-strength magnetic fields, and the deformation cannot be maintained after the magnetic field is removed, severely restricting the improvement of actuator energy efficiency and application capabilities. Therefore, breaking through the existing torque competition mechanism to achieve rapid, reversible large deformations and state self-maintenance under low magnetic fields has become a crucial breakthrough point for promoting the technological innovation and development of magnetically controlled soft actuators.

Research Methods

Addressing the above challenges, inspired by the phenomenon that "contact lenses can be easily inverted," Professor Li Liang's team proposed a novel magnetically controlled deformation method that integrates hemispherical shell-type bistable soft structures and a magnetic-induced instability mechanism. They constructed a magneto-mechanical coupling system centered on high magnetic moment units (pre-magnetized under strong fields) and a bistable structure with low potential energy difference. Under an external magnetic field, a pulsed magnetic torque induces structural instability, driving the system to cross the energy barrier between the two stable states, thereby achieving morphological control. This strategy cleverly utilizes the structure's own elastic energy to dominate the stable state switching process, while using the magnetic field as a transient directional "trigger," thus eliminating the dependence on high-intensity magnetic fields and realizing large, rapid morphological transitions of the actuator under low magnetic fields.

Research Outcomes

Based on the aforementioned method and mechanism innovation, Professor Li Liang's team achieved large deformations with a deformation ratio (ratio of deformation height to radius) exceeding 0.8 under weak magnetic field conditions as low as 20 mT. This performance significantly surpasses reported levels of existing similar actuators (typically requiring >100 mT magnetic fields with deformation ratios <0.5) in terms of both driving magnetic field strength and deformation ratio. Furthermore, the bistable configuration switching time can be as low as 0.1 s. Simultaneously, the team developed a series of magnetically controlled soft actuator application systems, including a high-flow-rate soft diaphragm pump, programmable reconfigurable metasurface-like material arrays, and an anemone-like variable stiffness gripper, fully demonstrating the broad applicability of this actuation method in fields such as flexible actuation, programmable structures, and intelligent manipulation.

Research Significance

This work achieves a shift in the deformation control mechanism of magnetically controlled soft actuators from the traditional "continuous strong torque competition" to "transient low-field triggered transition," incorporating core advantages such as low-field driving, state self-locking, and instantaneous transition. This breakthrough provides new ideas for achieving "low energy input, strong field output" in application scenarios with space constraints, such as in vivo medical robots. It holds enlightening significance for the design of advanced soft actuators integrating bistable/multistable structures and will promote the practical application process of miniaturized, low-power soft actuator technologies.

Figure 1. Design concept and bidirectional reversible deformation control diagram of the magnetically controlled bistable soft actuator.

Figure 2. Dynamic response characteristics of the magnetically controlled bistable soft actuator under different magnetic field frequencies.

Team Introduction

Professor Li Liang's team has long been committed to basic theories, key technologies, and application research related to high magnetic fields. They led the construction of two major national science and technology infrastructures: the "11th Five-Year Plan" Pulsed High Magnetic Field Experimental Facility and the "14th Five-Year Plan" Optimization and Upgrade of the Pulsed High Magnetic Field Experimental Facility, establishing an internationally leading large-scale science facility for pulsed high magnetic fields. This achievement marks China's transition from having no access to ultra-high magnetic field extreme conditions, to following, and finally leading in this area. The team has been awarded the 2019 National Science and Technology Progress Award (First Class), the 2018 Hubei Provincial Science and Technology Progress Award (Special Class), and the 2022 Hubei Provincial Technology Invention Award (First Class). They have also been honored with titles such as "National Advanced Collective of Professional Technical Talents" and "China Youth May Fourth Medal Collective."

Keeping pace with major national and industrial demands, and relying on the large-scale science facility, the team actively conducts cutting-edge applied technology research in high magnetic fields. They have achieved a series of breakthroughs in multiple interdisciplinary fields, including in-situ magnetization and demagnetization of large permanent magnet equipment, electromagnetic forming manufacturing, magnetically controlled robots, and biomedical applications. Related work has been published in high-level domestic and international journals such as Nature Communications, Science Advances, International Journal of Machine Tools and Manufacture, and the IEEE series. The team has also guided students to win honors including the National Gold Award in the China International College Students' 'Internet+' Innovation Competition (2024, 2025) and the Special Award in the National College Student Robotics Technology Innovation Exchange Camp and Robot Competition.