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Reverse osmotic effect in active matter.

Hyeongjoo Row1, John F Brady1

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Summary
This summary is machine-generated.

In active matter systems, particle concentration and swim speed remain constant (nU=const) even with abrupt changes and Brownian motion at high Péclet numbers. This drives reverse osmotic flow from high to low concentration regions.

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Area of Science:

  • Physics
  • Soft Matter Physics
  • Active Matter Systems

Background:

  • Nonequilibrium active matter systems exhibit unique steady-state properties.
  • A known condition for steady state is nU=constant, relating number density (n) and active swim speed (U).

Purpose of the Study:

  • To investigate the validity of the nU=constant condition under abrupt spatial variations in activity.
  • To determine if this condition holds in the presence of thermal Brownian motion.
  • To explore the resulting fluid dynamics.

Main Methods:

  • Theoretical analysis of active matter systems.
  • Consideration of spatial variations in particle activity and swim speed.
  • Inclusion of thermal Brownian motion effects.
  • Analysis of systems with large Péclet numbers.

Main Results:

  • The condition nU=constant is demonstrated to hold even with abrupt spatial variations in swim speed.
  • This condition persists in the presence of thermal Brownian motion when the Péclet number is large.
  • Spatial variations in swim speed and concentration create a fluid pressure gradient.

Conclusions:

  • The study confirms the nU=constant condition in more complex active matter scenarios.
  • The derived pressure distribution drives a reverse osmotic flow, moving fluid from high to low concentration areas.
  • Findings offer insights into transport phenomena in active matter.