Fabrication of Fibers With Complex Features Using Thermal Drawing of 3D‐Printed Preforms

ABSTRACT High‐aspect‐ratio polymer materials are widely utilized in applications ranging from everyday materials to specialized equipment in industrial and medical fields. Traditional fabrication methods, such as extrusion and molding, face challenges in integrating diverse materials and achieving complex geometries. Thermal drawing transforms macroscale preforms into long, thin fibers while preserving cross‐sectional geometry, but preform fabrication remains a key limitation for producing complex and functional fiber architectures. Here, commercially available 3D printing is used as a fast, low‐cost route for fabricating polymer preforms for thermal drawing. By optimizing printing parameters, fibers with diameters down to 100 µm are produced while preserving complex cross‐sectional features at the micron scale. This capability enables miniaturization of interlocking fiber geometries designed for steerable catheter concepts. Beyond amorphous thermoplastics, semi‐crystalline polypropylene preforms are drawn to produce fibers that exhibit a fivefold greater tendon‐driven bending response than comparable polycarbonate fibers. Functional material integration is further demonstrated using magnetically loaded filament to produce magnetically responsive fibers for robotic applications. Longitudinal periodicity engineered into the preform produces tapered fibers with programmable stiffness gradients in a single fabrication run. This approach supports rapid translation from preform design to thermally drawn polymer fibers with complex geometries, broader material selection, and application‐specific functionality.