Magnetoactive Soft Drivers with Radial-Chain Iron Microparticles

Magnetic Bistable Dome Actuators for Soft Robotics with High Volume Capacity and Motion Stability

Magneto-responsive soft actuators hold significant promise in soft robotics due to their rapid responsiveness and untethered operation. However, controlling their deformations presents challenges because of their inherent flexibility and high degrees of freedom. Here, we present a magnetically driven bistable dome-shaped soft actuator that simplifies deformation by limiting it to two distinct states. The actuator achieves controlled state transitions by switching the orientation of external magnetic fields. We investigate the design strategy and magnetization styles of the dome-shaped soft actuator. Additionally, we analyze their effects on state transitions. The bistable dome undergoes significant volume changes reliably and smoothly during deformation, and its natural curvature makes it suitable for tasks involving rolling motion. We demonstrate the actuator's effectiveness in various applications, including an array of bistable domes for controlled actuation, a magnetically driven pulse pump with integrated check valves, and a ball-shaped bistable robot capable of efficient rolling locomotion and fluid manipulation. Our design significantly enhances the versatility and efficiency of bistable soft robotic systems, highlighting their potential for tasks such as liquid collection and release.

Programming and Reprogramming the Viscoelasticity and Magnetic Response of Magnetoactive Thermoplastic Elastomers

We present a novel type of magnetorheological material that allows one to restructure the magnetic particles inside the finished composite, tuning in situ the viscoelasticity and magnetic response of the material in a wide range using temperature and an applied magnetic field. The polymer medium is an A-g-B bottlebrush graft copolymer with side chains of two types: polydimethylsiloxane and polystyrene. At room temperature, the brush-like architecture provides the tissue mimetic softness and strain stiffening of the elastomeric matrix, which is formed through the aggregation of polystyrene side chains into aggregates that play the role of physical cross-links. The aggregates partially dissociate and the matrix softens at elevated temperatures, allowing for the effective rearrangement of magnetic particles by applying a magnetic field in the desired direction. Magnetoactive thermoplastic elastomers (MATEs) based on A-g-B bottlebrush graft copolymers with different amounts of aggregating side chains filled with different amounts of carbonyl iron microparticles were prepared. The in situ restructuring of magnetic particles in MATEs was shown to significantly alter their viscoelasticity and magnetic response. In particular, the induced anisotropy led to an order-of-magnitude enhancement of the magnetorheological properties of the composites.

Bio-inspired magnetic-driven folded diaphragm for biomimetic robot

Functional soft materials, exhibiting multiple types of deformation, have shown their potential/abilities to achieve complicated biomimetic behaviors (soft robots). Inspired by the locomotion of earthworm, which is conducted through the contraction and stretching between body segments, this study proposes a type of one-piece-mold folded diaphragm, consisting of the structure of body segments with radial magnetization property, to achieve large 3D and bi-directional deformation with inside-volume change capability subjected to the low homogeneous magnetically driving field (40 mT). Moreover, the appearance based on the proposed magnetic-driven folded diaphragm is able to be easily customized to desired ones and then implanted into different untethered soft robotic systems as soft drivers. To verify the above points, we design the diaphragm pump providing unique properties of lightweight, powerful output and rapid response, and the soft robot including the bio-earthworm crawling robot and swimming robot inspired by squid to exhibit the flexible and rapid locomotion excited by single homogeneous magnetic fields.

Shape-programmable magneto-active elastomer composites for curve and biomimetic behavior imitation

A programming methodology, which can be applied to soft-magnetic-material-based magneto-active elastomers (MAEs), to catch the predefined specific objective curves is proposed in this study. The objective curves have been equally separated into a couple of segments, which will be filled by the designed MAE elements. Furthermore, the designed MAE segments with different chain angles, in which the deformation orientation of each element under applied homogeneous magnetic fields has been investigated based on the designed experimental setup, are arrayed based on the proposed programming methodology to constitute the MAE composite to catch the orientation of the objective curve. The experimental results show that based on the proposed programming methodology, the MAE composites can describe different curves, which include harmonic, tangential and arc tangential functions under applied homogeneous magnetic fields with good agreement. Furthermore, on the basis of the proposed programming methodology, the MAE composites are utilized to mimic the typical biomimetic behavior (the peeking-up behavior of snakes and the flapping behavior of birds) with smooth curvature properties, in which the dynamic procedures present continuous curves.