Design and research on sequentially controlled magnetic-driven actuators with high stiffness by changing local EGaIn structural density

Magnetic-driven actuators (MDAs) are attracting increasing attention due to fast response and harmless interaction with humans. However, due to their low stiffness and difficulties in sequential magnetic control, MDAs are difficult to complete high-load tasks, and overcoming these obstacles can enable them to be exploited for a wide range of novel applications. In this work, sequentially controlled MDAs (SC-MDAs) with high stiffness were prepared by embedding a polydimethylsiloxane/liquid metal (PDMS/EGaIn) heating layer between magnetic memory polymer (MSMP) films. The variation of EGaIn structural density between different regions leads to temperature discrepancies, resulting in selective activation of specific regions for sequence control. The modulus of the optimized MSMP film at room temperature is 2.21 GPa, which exceeds that of other materials (about 1 MPa) by three orders of magnitude, demonstrating a substantial increase in stiffness. When the content of NdFeB is adjusted to 80 wt%, driving performance is adjusted by optimizing the length-thickness ratio of SC-MDAs. Each claw of the mechanical gripper exhibits a remarkable increase in load capacity, being able to carry 54 times its own weight, which is significantly higher compared to actuators made from other materials (about its weight). A hand-like actuator realizes the sequential control deformation by combining "fingers" with different heating properties.