Soft Organic Magnetic Materials Based on Macromolecular Radical Networks

Recent advances in magnetic materials have enabled new functions and capabilities in small-scale robotic devices. Most magnetic soft robots comprise heavy metals and rare-earth element magnetic particles and coatings, they often present corrosion, toxicity, and sustainability concerns as well as fabrication challenges. In contrast, organic magnetic materials present a metal-free opportunity to develop lightweight non-toxic magnets. We have developed metal-free, lightweight, intrinsically magnetic polymers based on stable organic free radicals. By directly incorporating nitroxide radical groups into a crosslinked polymer network, we can tune the magnetic and viscoelastic properties of the gels independently, opening the design space for metal-free magnetic gels. Although weaker than metallic ferromagnetic materials, these magnetic polymer gels exhibit lightweight, biocompatible, compressible, and bulk paramagnetic properties suitable for small-scale robotics applications, such as remote actuation, manipulation, and navigation through confined spaces. These intrinsically magnetic polymers open new opportunities for the design of fully organic magnetoactive materials and actuators for future biocompatible soft robotic applications.