Shape‐memory polymers have attracted attention as smart implant materials in recent years because they are lightweight, low‐cost, easily processable, and because they undergo large deformation. Here, cellulose nanofibers (CNFs) were used as a reinforcement for polyhydroxybutyrate (PHB)/polycaprolactone (PCL) composites to improve mechanical properties. The composites were investigated by rheological tests, differential scanning calorimetry, dynamic mechanical analysis, mechanical property tests, and shape‐memory tests. The printability of PHB/PCL/CNFs composites was demonstrated by using them to print interconnected porous structures with a gyroid surface. The results showed that the PHB/PCL (80:20) composites with 1 wt% CNF displayed the best comprehensive mechanical and shape‐memory properties. As a functional verification, a model of the self‐opening hand was fabricated by 3D printing, and its deformation and recovery capabilities were evaluated.

Polylactic acid (PLA) foam is widely regarded as an effective substitute for petroleum‐based foams. However, the fabrication of high‐expansive, lightweight, highly hydrophobic foams for oil/water separation remains a challenge. Here, an innovative method was developed to improve the foaming ability of PLA by introducing silane modified alkaline lignin (m‐LA), and a lightweight PLA foam with a high expansion ratio, high porosity, and high hydrophobic performance was successfully developed. The crystallization behavior, rheological properties, pore morphology, and oil/water separation performance of foams were evaluated. The results show that m‐LA not only improves the crystalline properties of PLA, but also plays an important nucleation role during the foaming. m‐LA increased the foaming ratio of PLA to 40.17 times, and reduced the apparent density of the foam to only 0.0303 g cm−3. The PLA foam has exponent hydrophobicity. The water contact angle is up to 130.0°, and the adsorption capacity of various organic solvents is 5.17–12.44 g g−1, because the surface energy of LA is reduced by silane modification. This study provides a new insight into the development of environment‐friendly PLA foams for oil/water separation applications.