A Biomimetic Soft Actuator Achieves Efficient Fluorescence via Covalent Cross-Linking

Area of Science:

• Materials Science
• Biomimetics
• Robotics

Background:

• Deep-sea observation requires soft robots with high luminescence in low-light conditions.
• Challenges exist in integrating fluorescent molecules into hydrogels due to dissociation and instability.
• Marine organism behaviors inspire novel biomimetic designs.

Purpose of the Study:

• To develop a biomimetic soft actuator with high fluorescence intensity and motion control for deep-sea applications.
• To overcome limitations of fluorescent molecule integration in hydrogel matrices.
• To achieve stable, long-lasting underwater devices.

Main Methods:

• Fabrication of a bilayer hydrogel actuator with a luminescent layer (PT4B-N) and a pH-responsive driving layer (PNPC).
• Covalent crosslinking of fluorescent molecules into the hydrogel matrix to enhance stability.
• Characterization of photoluminescence quantum yield (PLQY) and actuator motion (bending angle, cycle time).

Main Results:

• The luminescent layer achieved a high photoluminescence quantum yield (PLQY > 60%).
• The pH-responsive driving layer enabled motion control, with a maximum bending angle of approximately 360° and a cycle time of about 20 minutes.
• The actuator demonstrated synergistic fluorescence and shape change (SFSC) behavior, mimicking marine organisms.

Conclusions:

• The developed biomimetic soft actuator offers a promising solution for deep-sea observation by integrating high fluorescence and controlled motion.
• Covalent crosslinking effectively enhances the stability and service life of fluorescent hydrogel devices.
• The SFSC behavior opens new avenues for underwater robotics and sensing.