4D Printing of Multi‐Stimuli Responsive Protein‐Based Hydrogels for Autonomous Shape Transformations

• Published in: Advanced functional materials 2021-06, Vol.31 (23), p.n/a
• Main Authors: Narupai, Benjaporn, Smith, Patrick T., Nelson, Alshakim
• Format: Article
• Language: English
• Subjects: 4D printing; Actuators; Automation; Biodegradability; Biomedical materials; bovine serum albumin; Degradation; Enzymes; Hydrogels; Manufacturing engineering; Materials science; Morphing; multi‐stimuli responsive hydrogels; Polyisopropyl acrylamide; Proteins; protein‐based materials; Robotics; Serum albumin; shape transformations; Stimuli; Three dimensional printing
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202011012

Stimuli responsive hydrogels that can change shape in response to applied external stimuli are appealing for soft robotics, biomedical devices, drug delivery, and actuators. However, existing 3D printed shape morphing materials are non‐biodegradable, which limits their use in biomedical applications. Here, 3D printed protein‐based hydrogels are developed and applied for programmable structural changes under the action of temperature, pH, or an enzyme. Key to the success of this strategy is the use of methacrylated bovine serum albumin (MA–BSA) as a biodegradable building block to Pickering emulsion gels in the presence of N‐isopropylacrylamide or 2‐dimethylaminoethyl methacrylate. These shear‐thinning gels are ideal for direct ink write (DIW) 3D printing of multi‐layered stimuli‐responsive hydrogels. While poly(N‐isopropylacrylamide) and poly(dimethylaminoethyl methacrylate) introduce temperature and pH‐responsive properties into the printed objects, a unique feature of this strategy is an enzyme‐triggered shape transformation based on the degradation of the bovine serum albumin network. To highlight this technique, protein‐based hydrogels that reversibly change shape based on environmental temperature and pH are fabricated, and irreversibly altered by enzymatic degradation, which demonstrates the complexity that can be introduced into 4D printed systems. Multistimuli‐reponsive shape transformations are achieved using protein‐based hydrogels. Methacrylated bovine serum albumin with hydrophobic monomers can induce emulsion formation facilitating printability for direct ink write 3D printing. The 3D printed protein‐based hydrogels illustrate multistate shape changes under the action of temperature, pH, and enzymes.