Soft Multi-Material Magnetic Fibers and Textiles

Magnetically responsive soft materials are envisioned as the next building block in a myriad of applications including in minimally invasive surgical procedures, due to their untethered, safe, and versatile properties. However, constructing highly integrated magnetic fibers with extreme aspect ratios, that can be used as steerable catheters, endoscopes, or in medical textiles still remain a significant materials and processing challenge. Here, we present multi-material thermal drawing as a materials and processing platform to manufacture 10s of meters long, soft, ultra-stretchable, yet highly resilient magnetic fibers with a diameter as low as 300 µm¹. We identified magnetorheological elastomers with varied elastomeric matrices and hard magnetic micro-particles (neodymium–iron–cobalt–boron) as fillers. The composite exhibits rheological traits compatible with thermal drawing with tunable mechanical and magnetic properties, resulting in controllable actuation performance. By carefully controlling the viscosity during drawing, we show that we can slow down thermal reflow driven by surface tension and conserve micro-scale geometrical features and textures. To characterize the fibers post-drawing, we first used computed tomography that revealed a very good distribution of the fillers that was enhanced compared to the preform level. We then characterized the mechanical properties of the fibers that can withstand strains greater than 1000%. Subsequent magnetic hysteresis measurement revealed a strong magnetization on par with state-of-the-art magnetic composites, resulting in the ability to lift up to 370 times its own weight under an applied magnetic field. The fibers are also amenable to being magnetized with different orientations along their length, and to be weaved into functional textiles. The magnetic textile can be programmed to selectively shape morph and can sustain extreme mechanical deformation or several machine-wash cycles. They can apply force or pressure and could constitute a promising next generation of magnetic-based surgical tools and medical textiles for rehabilitation and soft prosthesis.<br/><br/>[1] Banerjee, Hritwick, et al. Soft Multimaterial Magnetic Fibers and Textiles. <i>Advanced Materials</i> (2023): 2212202.