Hydrodynamic instability and flow reduction in polymer brush coated channels.

Area of Science:

• Soft Matter Physics
• Fluid Dynamics
• Surface Science

Background:

• Polymer brushes are typically passive at equilibrium.
• Under fluid flow, polymer brushes exhibit complex behavior involving filamentous structures and fluid interactions.
• Understanding this dynamic behavior is crucial for applications involving coated surfaces.

Purpose of the Study:

• To investigate the hydrodynamic response of polymer brushes under fluid flow using numerical simulations.
• To quantify the fluid flow reduction within a polymer-brush coated channel at low Reynolds numbers.
• To elucidate the mechanism behind the amplified flow reduction observed in dynamic polymer brush systems.

Main Methods:

• Numerical simulations of polymer brush behavior in a fluid flow channel.
• Analysis of hydrodynamic response at low Reynolds numbers.
• Investigation of the polymer brush-liquid interface morphology and its elastic properties.

Main Results:

• A significant reduction in fluid flow velocity was observed inside the polymer-brush coated channel.
• The observed flow reduction was substantially greater than predicted by models considering only reduced channel width.
• Morphological instability of the polymer brush-liquid interface, originating from elastic stress release, was identified as the cause of amplified flow reduction.

Conclusions:

• The dynamic morphological instability of polymer brushes under flow leads to amplified fluid velocity reduction.
• This instability dissipates more energy than a flat interface, explaining the enhanced flow damping.
• The findings provide a theoretical explanation for recent experimental observations of polymer brush hydrodynamic behavior.