Adaptive Magnetoactive Soft Composites for Modular and Reconfigurable Actuators

Abstract

Magnetoactive soft materials, typically composed of magnetic particles dispersed in a soft polymer matrix, are finding many applications in soft robotics due to their reversible and remote shape transformations under magnetic fields. To achieve complex shape transformations, anisotropic, and heterogeneous magnetization profiles must be programmed in the material. However, once programmed and assembled, magnetic soft actuators cannot be easily reconfigured, repurposed, or repaired, which limits their application, their durability, and versatility in their design. Here, magnetoactive soft composites are developed from squid-derived biopolymers and NdFeB microparticles with tunable ferromagnetic and thermomechanical properties. By leveraging reversible crosslinking nanostructures in the biopolymer matrix, a healingassisted assembly process is developed that allows for on-demand reconfiguration and magnetic reprogramming of magnetoactive composites. This concept in multi-material modular actuators is demonstrated with programmable deformation modes, self-healing properties to recover their function after mechanical damage, and shape-memory behavior to lock in their preferred configuration and un-actuated catch states. These dynamic magnetic soft composites can enable the modular design and assembly of new types of magnetic actuators, not only eliminating device vulnerabilities through healing and repair but also by providing adaptive mechanisms to reconfigure their function on demand.

Triple-Responsive Soft Actuator with Plastically Retentive Deformation and Magnetically Programmable Recovery

“…Due to the ferromagnetic properties of NdFeB (high remanence), the innovative moment will be conserved when the external field is removed, thus resulting in programmable magnetization profiles. 41 For example, the rolling robot will be attracted when a reverse magnetic pole (≈ 200 mT) is placed at the bottom of the rolling robot. When the magnetic poles rotate, the rolling robot also rotates to align its own torque with the magnetic field below the substrate (Figure 5b,c).…”

“…The rolling robot can either roll as the magnet poles change, or change direction as the magnet changes direction. Due to the ferromagnetic properties of NdFeB (high remanence), the innovative moment will be conserved when the external field is removed, thus resulting in programmable magnetization profiles . For example, the rolling robot will be attracted when a reverse magnetic pole (≈ 200 mT) is placed at the bottom of the rolling robot.…”

4D Printing of Ultrastretchable Magnetoactive Soft Material Architectures for Soft Actuators

“…A magnetically actuated gripper with grasping and transport capabilities is useful as a soft actuator. − Figure a shows the 4D printed MSM architecture, designed with hinges and protuberances to enhance the folding and grasping for efficient transportation (Figure S7). The magnetization profile was obtained by magnetizing the architecture in an inclined state to induce an oblique flux distribution.…”

Reconfigurable modular soft robots with modulating stiffness and versatile task capabilities

“…Most commonly used connectivity mechanisms rely on mechanical, magnetic, adhesive, and vacuum principles [9]. Among these, the magnetic mechanism is an attractive option as it can actively control the interconnection of modules by using either permanent magnets with predefined magnetic fields [8], electropermanent magnets (EPM) that allow tunable connectivity based on the applied electric current [30], or magnetic soft composites with pre-programmable magnetization [31]. While these magnetic devices have promising potential in modular robotics, their current applications have two major limitations: (1) the non-articulating connection between the units that hinder the structural reconfigurability and stiffness tuning, and (2) the added rigidity to the soft modular unit itself from the embedded hard components.…”