Spider-Silk-Like Single-Fiber Actuators with Two Actuation Modes Driven by Water.

Area of Science:

• Biomaterials Science
• Robotics Engineering
• Materials Science

Background:

• Soft actuators are crucial for soft robot movement.
• Fiber actuators offer advantages like flexibility and lightweight design.
• Keratin's hierarchical structure, with reversible hydrogen bonds and conformational changes, is key.

Purpose of the Study:

• To propose single-fiber actuators with programmable water-driven actuation.
• To leverage keratin's intrinsic properties for enhanced actuator performance.
• To explore dual-mode responsiveness in keratin fibers.

Main Methods:

• Utilizing the hierarchical structure of keratin.
• Investigating reversible hydrogen bonds and secondary structure changes (α-helix, β-sheet).
• Observing supercontraction and cyclic contraction-extension responses to water.

Main Results:

• Keratin fiber actuators demonstrated programmable water-driven actuation.
• Two responsive modes were observed: initial supercontraction and cyclic hydration-dehydration response.
• Actuation energy significantly exceeded that of natural muscles, liquid crystal elastomers, and composite actuators.

Conclusions:

• Keratin fibers possess intrinsic dual-mode water responsiveness.
• This property enables high-performance bio-based soft actuators.
• The findings enhance keratin's value and inspire future soft actuator designs.