This work proposes a facile fabrication strategy of polyurethane (TPU) tissue‐engineering scaffold with hierarchical structure, designed by combination of the fused deposition modeling (FDM) 3D printing and supercritical microcellular foaming by carbon dioxide (CO2). Further surface modification of TPU scaffold with graphene oxide (GO) was carried out by in situ polymerization of polydopamine (PDA) to ensure stable loading of GO with antibacterial properties. The influence of 3D‐printing temperature and speed on the microcellular cell morphology of TPU scaffold was investigated and optimized. The microcellular foaming and expansion process was indicated to compensate mechanical loss because of the gaps of stacking layers by FDM printing, and the reported tensile strength of 28 MPa matched well with that of natural cartilage tissue constructs. More interesting, the formation of interconnected open pores on the surface of foamed TPU scaffold shows much more enhanced cell adhesion because of the bigger specific surface area of microcellular structure. Similarly, the foamed TPU scaffold exhibits good absorption of GO nanosheets by the synthesized PDA on the surface and antibacterial properties, compared with the unfoamed TPU scaffold. This work offers a strategy for designing and manufacturing polymer tissue‐engineering scaffold with hierarchical structure and good antibacterial property.

Biodegradable polylactic acid (PLA) foams with open-cell structures are good candidates for oil–water separation. However, the foaming of PLA with high-expansion and uniform cell morphology by the traditional supercritical carbon dioxide microcellular foaming method remains a big challenge due to its low melting strength. Herein, a green facile strategy for the fabrication of open-cell fully biodegradable PLA-based foams is proposed by introducing the unique stereocomplexation mechanism between PLLA and synthesized star-shaped PDLA for the first time. A series of star-shaped PDLA with eight arms (8-s-PDLA) was synthesized with different molecular weights and added into the PLLA as modifiers. PLLA/8-s-PDLA foams with open-cells structure and high expansion ratios were fabricated by microcellular foaming with green supercritical carbon dioxide. In detail, the influences of induced 8-s-PDLA on the crystallization behavior, rheological properties, cell morphology and consequential oil–water separation performance of PLA-based foam were investigated systemically. The addition of 8-s-PDLA induced the formation of SC-PLA, enhancing crystallization by acting as nucleation sites and improving the melting strength through acting as physical cross-linking points. The further microcellular foaming of PLLA/8-s-PDLA resulted in open-cell foams of high porosity and high expansion ratios. With an optimized foaming condition, the PLLA/8-s-PDLA-13K foam exhibited an average cell size of about 61.7 μm and expansion ratio of 24. Furthermore, due to the high porosity of the interconnected open cells, the high-absorption performance of the carbon tetrachloride was up to 37 g/g. This work provides a facile green fabrication strategy for the development of environmentally friendly PLA foams with stable open-cell structures and high expansion ratios for oil–water separation.

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