4D printing of architected metal structures via biodegradation

4D printing, integrating the temporal dimension into 3D printing, offers transformative potential for biomedical engineering. Yet its application to metals is constrained by the scarcity of suitable alloys and the requirement for harsh external stimuli to trigger shape change. Here, we introduce 4D printed architected metal structures (4DAMS) driven by controlled biodegradation. The 4DAMS combine biodegradable constraints (e.g., Mg or Zn) with biometals of higher corrosion potential (e.g., Ti). Upon selective constraint degradation, the structures recover their original geometry—via stretching, bending, or expansion—generating programmable recoil forces tuned through structural design parameters. When developed as scaffolds for bone implants, 4DAMS exhibit excellent cytocompatibility and, in vivo, promote superior bone regeneration through the synergistic effects of bioactivity and mechanical stimulation. This strategy establishes a new paradigm in 4D metal printing, enabling bioactive, self-restoring implants with broad applicability across biomedical engineering.