Magnetoactive bistable soft actuators for programmable large shape transformations at low magnetic fields

As the demand for advanced actuation strategies in soft robotics and intelligent material systems grows, magnetoactive soft actuators have attracted increasing attention for their ability to achieve flexible shape transformations through remote and untethered control. However, existing designs typically rely on continuous high magnetic fields to generate large deformations, limiting both efficiency and applicability, especially under constrained boundary conditions. Here we report a hemispherical bistable soft actuator embedded with magnetic microparticles, which enables substantial shape changes under low-intensity pulsed magnetic torques and remains stable in two configurations without external fields. We analyze the relationship between design parameters and actuator performance to clarify the bistable mechanism, and show that the actuator can achieve a large shape change ratio exceeding 0.8 under magnetic fields below 20 mT. We further demonstrate its versatility through three applications: a high-efficiency soft pump with closed-loop fluid control, a reprogrammable metamaterial, and a variable-stiffness soft gripper.