Sol-gel transition programmed self-propulsion of chitosan hydrogel

Area of Science:

• Soft Matter Physics
• Materials Science
• Chemical Engineering

Background:

• Active soft materials demonstrate complex dynamics, including pulsation and deformation.
• Chitosan-based hydrogels are versatile materials with potential for autonomous motion.

Purpose of the Study:

• To investigate the propulsion mechanisms and dynamics of in situ prepared ethanol-containing chitosan gels.
• To understand the influence of chitosan concentration on gel motion, shape, and stability.

Main Methods:

• In situ preparation of ethanol-containing chitosan gels.
• Observation and analysis of gel propulsion dynamics (continuous and intermittent motion).
• Characterization of velocity, projection area, and shape changes with varying chitosan concentrations.

Main Results:

• Chitosan gels exhibit continuous and intermittent propulsion in ethanol.
• Gel active life scales linearly with fuel level.
• Maximal velocity and projection area decrease with increasing chitosan concentration.
• Low polymer content leads to thin propelling platelets and suppressed intermittent motion.
• Fast-accelerating thin gels undergo shape transformations, including splitting and fission.

Conclusions:

• Chitosan concentration is a critical factor controlling the propulsion and morphological dynamics of these active soft materials.
• The observed fission behaviors offer insights into self-organization and pattern formation in active matter.
• These findings contribute to the understanding and design of novel self-propelling soft robots and actuators.