Self-healing and reconfigurable protein-based magnetic actuators

Soft microrobots can achieve controlled motion and shape changing upon actuation, and thus are capable of performing non-invasive surgery in the human body. Among soft actuation systems, magnetic actuation is advantageous for healthcare applications since magnetic fields can penetrate tissue, and can generate both pulling forces and torques remotely. One current challenge is that magnetic microrobots typically have limited actuation modes, which are determined by the actuation field and the internal magnetization profile of the robot. In this study, we developed a magnetic soft composite based on squid-derived proteins and rare-earth magnetic particles with discrete magnetization profiles, and used self-healing to reconfigure their magnetization and actuation modes. The self-healing properties of the squid-derived protein matrix enables the rearrangement of modular components with different magnetic properties. By tailoring the composition, the anisotropy of the thermo-mechanical properties, the geometrical robot design, and the actuation magnetic field, we demonstrate control over complex robot deformations, and reversible reconfiguration of actuation modes. This work opens up the design space of magnetic soft robots and their reconfigurable actuation modes via the discrete programming of the magnetization directions and intensities throughout the microrobot body. This freedom in design can provide key advantages in soft and small-scale actuation to perform specific tasks in confined environments, with application in healthcare and industrial micromanipulation.