4D Printed Protein‐AuNR Nanocomposites with Photothermal Shape Recovery

Abstract 4D printing is the 3D printing of objects that change chemically or physically in response to an external stimulus over time. Photothermally responsive shape memory materials are attractive for their ability to undergo remote activation. While photothermal methods using gold nanorods (AuNRs) are used for shape recovery, 3D patterning of these materials into objects with complex geometries using degradable materials is not addressed. Here, the fabrication of 3D printed shape memory bioplastics with photo‐activated shape recovery is reported. Protein‐based nanocomposites based on bovine serum albumin (BSA), poly (ethylene glycol) diacrylate (PEGDA), and AuNRs are developed for vat photopolymerization. These 3D printed bioplastics are mechanically deformed under high loads, and the proteins served as mechano‐active elements that unfolded in an energy‐dissipating mechanism that prevented fracture of the thermoset. The bioplastic object maintained its metastable shape‐programmed state under ambient conditions. Subsequently, up to 99% shape recovery is achieved within 1 min of irradiation with near‐infrared (NIR) light. Mechanical characterization and small angle X‐ray scattering (SAXS) analysis suggest that the proteins mechanically unfold during the shape programming step and may refold during shape recovery. These composites are promising materials for the fabrication of biodegradable shape‐morphing devices for robotics and medicine.