Microgel-Crosslinked Thermo-Responsive Hydrogel Actuators with High Mechanical Properties and Rapid Response

Area of Science:

• Materials Science
• Polymer Chemistry
• Soft Robotics

Background:

• Smart hydrogels are crucial for applications like soft robotics and smart devices.
• High mechanical strength and rapid response rates are key for hydrogel actuators.
• Existing hydrogels often lack sufficient toughness or speed for demanding applications.

Purpose of the Study:

• To synthesize robust hydrogels with enhanced response rates.
• To investigate the tunability of hydrogel mechanical properties and thermal responsiveness.
• To demonstrate the application potential of these hydrogels in actuator designs.

Main Methods:

• Synthesized poly(N-isopropylacrylamide) (PNIPAM) hydrogels using vinyl-functionalized PNIPAM microgels as macro-crosslinkers and N-isopropylacrylamide monomers.
• Adjusted mechanical strength and response rate by varying monomer and crosslinker ratios.
• Tuned the lower critical solution temperature (LCST) via copolymerization with sodium methacrylate.
• Fabricated thermo-responsive bilayer hydrogels using layer-by-layer assembly.

Main Results:

• Achieved PNIPAM hydrogels with compression strength up to 7.13 MPa.
• Demonstrated significantly enhanced response rates compared to conventional chemically crosslinked hydrogels.
• Successfully tuned LCST and mechanical properties.
• Created bilayer hydrogels exhibiting anisotropic structures and asymmetric responses.

Conclusions:

• Developed tough, rapidly responding PNIPAM-based hydrogels with tunable properties.
• Bilayer hydrogels show promise for actuator applications, demonstrated by clamp and petal-mimicking flower prototypes.
• These findings advance the development of advanced smart materials for soft robotics and devices.