Pressure responsive gating in nanochannels coated by semiflexible polymer brushes

Area of Science:

• Fluid dynamics
• Polymer physics
• Soft matter physics

Background:

• Semiflexible polymer brushes are used to coat surfaces in microfluidic devices.
• In poor solvent conditions, polymers grafted to opposing walls can form bundles across channels.
• Understanding flow behavior within such confined geometries is crucial for device design.

Purpose of the Study:

• To investigate liquid flow dynamics in slit channels coated with polymer brushes.
• To explore the relationship between external force, flow rate, and polymer brush morphology.
• To identify potential mechanisms for flow control in micro- and nano-fluidic systems.

Main Methods:

• Coarse-grained molecular-dynamics simulations were employed.
• Liquid flow was simulated in a slit channel with polymer brush-coated walls.
• A constant body force was applied to particles to induce flow.

Main Results:

• A non-linear relationship between external force and flow rate was observed.
• Morphological changes in polymer brushes, specifically bundle breaking, were linked to flow rate increases.
• The system exhibited a pressure-responsive gate behavior due to brush restructuring.
• Flow rate showed a non-monotonic dependence on polymer bending rigidity, with an optimal persistence length.
• The force threshold for morphological changes scaled linearly with grafting density.

Conclusions:

• Polymer brush morphology significantly impacts liquid flow in confined geometries.
• The observed pressure-responsive gate effect offers a novel mechanism for flow control.
• These findings have implications for designing advanced micro- and nano-fluidic devices with tunable flow properties.