Programmable and Bidirectional Bending of Soft Actuators Based on Janus Structure with Sticky Tough PAA-Clay Hydrogel

Area of Science:

• Materials Science
• Polymer Science
• Robotics

Background:

• Developing hydrogel actuators with facile preparation, rapid actuation, and versatile actions remains a significant challenge.
• Existing methods often struggle to balance toughness, adhesion, and controlled responsiveness in hydrogel-based soft actuators.

Purpose of the Study:

• To present a facile sticking method for preparing Janus bilayer and multilayer hydrogel actuators.
• To engineer hydrogel actuators with rapid response times and precisely controlled actuating directions.
• To demonstrate the versatility of these hydrogel actuators through various complex soft robotic applications.

Main Methods:

• A tough and adhesive poly(acrylic acid)-clay (PAA-clay) hydrogel was prepared using combined physical and chemical cross-linking reagents.
• The PAA gel was further reinforced by cross-linking with Fe³⁺, creating hydrogels with distinct cross-linking densities.
• Two hydrogel layers with different swelling capabilities and moduli were stuck together to form bilayer actuators responsive to pH and ionic strength.

Main Results:

• The PAA-clay hydrogel exhibited enhanced toughness and adhesion.
• The fabricated hydrogel actuators showed rapid response times (within minutes) and precisely controlled actuating directions.
• Demonstrated applications included a bidirectional bending flytrap, a multi-action gel hand (grasp, open, gesture), and a word-writing actuator.

Conclusions:

• The facile sticking method enables the creation of versatile and programmable soft actuators.
• This approach, utilizing adhesive PAA gel with other stimuli-responsive hydrogels, opens new avenues for advanced soft robotic systems.
• The developed hydrogel actuators offer a promising platform for applications requiring rapid, controlled, and adaptable movements.