Flow-driven Surface Instabilities of Tubular Chitosan Hydrogel

Area of Science:

• Materials Science
• Biomaterials Engineering
• Fluid Dynamics

Background:

• Shear stress from fluid flow can induce symmetry breaking in spatial structures.
• Chitosan, a versatile biopolymer, is a candidate for creating novel soft biomaterials.
• Controlling surface morphology is crucial for biomaterial applications.

Purpose of the Study:

• To investigate surface instabilities on chitosan tubes induced by fluid injection.
• To characterize the resulting patterns (wrinkles and folds) and their dependence on flow rate and solution concentration.
• To establish scaling laws for pattern wavelength and amplitude.

Main Methods:

• Injection of acidic chitosan solutions into sodium hydroxide solutions.
• Observation and characterization of surface pattern formation under varying flow rates and alkaline concentrations.
• Analysis of pattern wavelength and amplitude in relation to tube properties.

Main Results:

• Slow flow rates produced a wrinkle-to-fold transition, forming banded structures along the flow direction.
• Higher injection rates resulted in coexisting wrinkle and fold modes.
• Increased alkaline concentration stabilized patterns into periodic wrinkles.

Conclusions:

• Fluid flow-induced mechanical instabilities can be leveraged to create patterned chitosan tubes.
• The study provides a template-free, in situ method for fabricating soft biomaterials with tunable surface morphologies.
• This approach offers a new route for designing advanced biomaterials with specific surface features.