Fabrication of Robust Superhydrophobic Surfaces on 3D-Printed Polymer Scaffolds via Confined Phase Separation.

3D printing enables the fabrication of complex, customizable biomedical polymer structures. The integration of superhydrophobicity─known for its unique self-cleaning, antibacterial, and anticoagulant properties─can significantly enhance the functionality of 3D-printed polymer in biomedical applications. However, conventional coating-based approaches for imparting superhydrophobicity suffer from poor mechanical stability due to weak adhesion between the coating layer and the substrate. In this study, we present a solvent transfer-induced phase separation (STIPS) strategy to generate robust superhydrophobic surfaces on 3D-printed polymer scaffolds. This approach involves initially swelling the scaffold surface in a good solvent, followed by immersion in a poor solvent to induce phase separation, thereby forming a micro/nanoporous surface layer essential for achieving superhydrophobicity. The resulting superhydrophobic structures are seamlessly integrated with the bulk material, conferring excellent mechanical durability, as demonstrated by tape-peeling and ultrasonication tests. Importantly, unlike conventional coatings that are limited to flat surfaces, the STIPS method is applicable to complex 3D geometries, including the inner surfaces of hollow vascular scaffolds. Notably, the treated superhydrophobic scaffolds exhibited strong resistance to bacterial adhesion and effective anticoagulant performance, attributed to their pronounced water repellency. This simple yet versatile strategy offers a promising route for expanding the biomedical utility of 3D-printed biodegradable scaffolds, particularly in applications requiring reduced microbial contamination, thrombosis prevention, and low protein fouling.