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Updated: May 14, 2025
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Forming, Confining, and Observing Microtubule-Based Active Nematics
Published on: January 13, 2023
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Cooperativity of Confined Nematic Microswimmers: From One to Many
Shubhadeep Mandal1, Thomas J Mason2, Anthony C Croft3
1Indian Institute of Science, Department of Mechanical Engineering, Bengaluru 560012, India.
Physical Review Letters
|April 11, 2025
Summary
Controlling microswimmers in liquid crystals is challenging. This study reveals how confinement and fluid properties influence their motion, enabling new active matter applications.
Area of Science:
- Active Matter Physics
- Soft Condensed Matter
- Microhydrodynamics
Background:
- Controlling microswimmer behavior is crucial for developing novel active matter applications.
- Geometric confinement is a common strategy for controlling soft matter systems.
- The dynamics of microswimmers in anisotropic fluids, particularly near solid interfaces, are less understood than in Newtonian fluids.
Purpose of the Study:
- To investigate the dynamical behavior of microswimmers in a nematic liquid crystal confined by solid walls.
- To understand the influence of confinement, propulsion strength, and fluid anisotropy on microswimmer dynamics.
- To explore cooperative behaviors and control mechanisms in active nematic systems.
Main Methods:
- Nematic multiparticle collision dynamics (NMCD) simulations were employed to model microswimmer behavior.
- Analytical modeling was used to complement simulation results and elucidate underlying physical mechanisms.
- The study considered isolated squirmers and systems with multiple interacting squirmers.
Main Results:
- A rich phase diagram was identified for isolated squirmers, including oscillatory dynamics for weak pushers, dependent on propulsion strength and confinement.
- Theoretical models indicate that force dipole, source dipole, and source quadrupole singularities are necessary for oscillations in nematic fluids, unlike in isotropic fluids.
- Cooperative behavior emerged in pusher-type squirmers with increasing numbers, while pullers' flow fields interfered with each other's motion.
Conclusions:
- The interplay between nematodynamic torque, wall-induced elastic repulsion, and active flows provides opportunities for controlling and transporting microswimmers in active nematic systems.
- Anisotropic fluid properties and geometric confinement significantly alter microswimmer dynamics compared to isotropic fluids.
- The findings offer a pathway for designing advanced microswimmer-based devices and applications.
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