A novel fabrication method for gradient-structured PNIPAM-based hydrogels

Both sodium alginate-gelatin and PNIPAM demonstrate excellent biocompatibility, exhibiting promising application prospects in biomedical fields. To develop hydrogel actuators with superior biocompatibility, we synthesized a novel intelligent gradient material formed by alginate, gelatin and NIPAM. This gradient-structured hydrogel is formed through the mutual interpenetration of the upper and lower hydrogel layers during the synthesis process. Rheological analysis was conducted to characterize the temperature-sensitive properties of sodium alginate-gelatin during gelation. By precisely controlling the gelation time of sodium alginate-gelatin systems, we achieved effective modulation of the responsive rate in the smart hydrogel. Experimental results revealed that hydrogels synthesized via free radical polymerization with a 5-minute sodium alginate-gelatin gelation duration exhibited optimal responsiveness, attaining a maximum bending rate of 60 °/s and achieving the greatest curvature angle of 1050°. This work may provide new insights for applications in biomedical fields and controlled drug release.