A Biocompatible and Self-Healable 3D-Printed Bidirectional Hydrogel Actuator with Needle Injectability

Area of Science:

• Materials Science
• Biomedical Engineering
• Polymer Chemistry

Background:

• Multifunctional hydrogels are crucial for advanced material applications, especially biocompatible actuators.
• Current biocompatible actuators face challenges in integrating toughness, self-healing, and reversible bidirectional actuation.

Purpose of the Study:

• To develop a 3D-printable, biocompatible bilayer hydrogel actuator with reversible bidirectional actuation.
• To integrate toughness, self-healing, and reversible bidirectional actuation into a single hydrogel system.

Main Methods:

• Fabrication of a novel poly(N-isopropylacrylamide)-gelatin methacryloyl (PNIPAM-GelMA; PNG) hydrogel as the active layer.
• Utilizing photo-cross-linking for hydrogel formation and small-angle X-ray scattering for microstructural analysis.
• 3D printing of a bilayer actuator with PNG as the active layer and GelMA as the passive layer.

Main Results:

• The PNG hydrogel exhibited self-healing, good elasticity (storage modulus ~13 kPa), and toughness (up to 240% shear strain).
• The 3D-printed bilayer actuator demonstrated reversible bidirectional actuation and fine needle injectability.
• A self-healable actuator was achieved by pairing the PNG active layer with a self-healable passive layer, retaining significant bending angles after repair.

Conclusions:

• The developed PNG hydrogel system successfully integrates toughness, self-healing, and reversible bidirectional actuation.
• This multifunctional hydrogel actuator addresses key limitations in current biocompatible actuators.
• The findings represent significant progress for developing advanced actuators in biomedical applications.