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Casimir effect in active matter systems.

D Ray1, C Reichhardt2, C J Olson Reichhardt2

  • 1Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA and Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA.

Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
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PubMed
Summary
This summary is machine-generated.

Active matter particles in Casimir geometries experience an attractive force between walls, intensifying with longer run lengths. This force results from particle depletion between walls due to motion and shadowing effects.

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Area of Science:

  • Physics
  • Soft Matter Physics
  • Statistical Mechanics

Background:

  • Active matter systems exhibit complex behaviors driven by self-propulsion.
  • Casimir effects in confined geometries can lead to forces between boundaries.

Purpose of the Study:

  • To numerically investigate the interaction forces between two finite parallel walls in the presence of run-and-tumble active matter.
  • To elucidate the mechanisms driving attraction and repulsion in such active matter-based Casimir geometries.

Main Methods:

  • Numerical simulations of run-and-tumble particles in confined geometries.
  • Analysis of particle distribution and force calculations between walls.

Main Results:

  • An attractive force between walls was observed, increasing with particle run length.
  • The attraction shows an exponential dependence on wall separation, driven by particle depletion.
  • This attraction is robust for wall lengths comparable to or smaller than the run length and is minimally affected by steric interactions.

Conclusions:

  • Run-and-tumble active matter can generate significant Casimir-like forces in confined geometries.
  • Particle motion and geometric shadowing are key to the observed attractive forces.
  • Tunable attraction-to-repulsion crossovers can be achieved by varying wall separation and length.