Thermal-Responsive Hydrogel Actuators with Photo-Programmable Shapes and Actuating Trajectories

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Thermal-responsive hydrogels are widely researched for actuation but often exhibit monotonous behaviors due to fixed shapes.
• Existing hydrogel actuators lack programmability in their shape and internal actuating pathways, limiting their application scope.

Purpose of the Study:

• To develop novel thermal-responsive hydrogels with programmable external shapes and internal actuating trajectories.
• To achieve tunable volume phase transition temperatures and enable complex, multi-functional shape-changing behaviors.

Main Methods:

• Synthesized poly(isopropylacrylamide-co-2-(dimethylamino)ethyl methacrylate)/alginate hydrogels with tunable compositions.
• Utilized Fe3+-carboxylate tri-coordinates for photo-responsive shape memory and gradient crosslinking for thermal actuation.
• Controlled gradient structure evolution to regulate actuating amplitude.

Main Results:

• Achieved tunable volume phase transition temperatures ranging from 32 to over 50 °C.
• Demonstrated photo-responsive shape memory and gradient crosslinking for controlled thermal actuation.
• Combined functionalities enabled intricate shape-changing behaviors, exemplified by a programmable hook.

Conclusions:

• The developed hydrogels offer programmable external shapes and internal actuating trajectories, overcoming limitations of monotonous actuation.
• The strategy of combining photo-responsive shape memory and gradient crosslinking provides a versatile platform for advanced hydrogel actuators.
• This approach can be extended to engineer hydrogels with more sophisticated actuating capabilities for diverse applications.