Characterization and Printability Study of 3D Printed Polyurethane/Polycaprolactone Using IP-3D Printing for Tendon and Ligament

Tendon and ligament injuries, often resulting in acute or chronic pain, necessitate tissue engineering approaches that employ porous polymer scaffolds with optimized physical and mechanical properties to restore function. This research focuses on the fabrication of such scaffolds using immersion precipitation 3D printing (IP-3DP). In this process, a polymer solution is extruded into a nonsolvent bath, triggering rapid phase separation and pore formation without the need for postprocessing. The technique accommodates a broad spectrum of solvent vapor pressures, providing flexibility in scaffold design. Polyurethane (PU), known for its biocompatibility, biodegradability, and flexibility, is blended with polycaprolactone (PCL) to create a composite material with enhanced mechanical toughness, making it suitable for tendon and ligament regeneration. The IP-3DP process employs nonsolvent-induced phase separation (NIPS) to generate intricate 3D porous structures. The exchange between the solvent and nonsolvent induces distinct pore morphologies depending on the exchange rate: high rates lead to spinodal decomposition with finger-like structures, while lower rates favor nucleation and growth mechanisms, resulting in micropores. This study assesses the printability of PU/PCL composites using various nonsolvents, analyzing their impact on strand uniformity, porosity, and pore size. Preliminary results show that pore diameters range from 2 to $50 \mu \mathrm{~m}$, depending on the nonsolvent employed.