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Tractionless Self-Propulsion of Active Drops.

Aurore Loisy1, Jens Eggers1, Tanniemola B Liverpool1

  • 1School of Mathematics, University of Bristol, Bristol BS8 1UG, United Kingdom.

Physical Review Letters
|January 11, 2020
PubMed
Summary

Active liquid drops exhibit novel tractionless self-propulsion. Their motion, driven by nematic director winding, offers insights into efficient cell migration in complex biological environments.

Area of Science:

  • Physics of active matter
  • Soft matter physics
  • Biophysics

Background:

  • Active liquids exhibit complex behaviors, including self-propulsion.
  • Understanding cell migration in crowded environments is crucial for developmental biology and disease research.
  • Traction-based propulsion is a common model, but alternative mechanisms may exist.

Purpose of the Study:

  • To investigate a novel mode of self-propulsion in active liquid drops.
  • To analyze the role of nematic director fields in drop motion.
  • To explore the physical origins and potential biological relevance of tractionless propulsion.

Main Methods:

  • Analytical modeling of active nematic drop hydrodynamics.
  • Numerical simulations to solve equations of motion.

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  • Comparison with physics of bacterial suspensions.

    • Main Results:

    • A self-propelling solution for active nematic drops was identified.
    • The motion is tractionless, imparting no local stress on the substrate.
    • The direction of propulsion is dictated by the nematic director field's winding.

    Conclusions:

    • Tractionless self-propulsion is a viable mechanism for active drops.
    • This mode of motion shares physical principles with zero-viscosity phenomena in bacterial suspensions.
    • Topologically protected tractionless propulsion offers a robust model for efficient cell migration in biological tissues.