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Spontaneous rotation and propulsion of suspended capsules in active nematics

Júlio P. A. Santos1,2,3, Margarida M. Telo da Gama1,2,4, and Rodrigo C. V. Coelho1,2,5,*

  • *Contact author: rcvcoelho@cbpf.br
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Phys. Rev. E 113, L043401 – Published 1 April, 2026

DOI: https://doi.org/10.1103/nvrc-3mlt

Abstract

We investigate the dynamics of elastic capsules suspended in two-dimensional active nematic fluids using lattice Boltzmann simulations. The capsules, modeled as flexible membranes enclosing active internal regions, exhibit a rich variety of behaviors shaped by their geometry and the interplay between internal and external activity. Circular capsules with active interiors undergo persistent rotation driven by internally confined +1/2 topological defects. Axisymmetric capsules, such as boomerangs, develop directed motion along their axis of symmetry due to unbalanced active forces generated by defect distributions near their boundaries. We further show that capsule flexibility suppresses motility and rotation, as active stresses are dissipated into shape deformations. These findings reveal how shape, deformability, and defect dynamics cooperate to produce emergent motility in soft active matter, with potential applications in the design of microswimmers and drug delivery vehicles.

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Information

Phys. Rev. E 113, L043401– Published 1 April, 2026
  • Received 18 October 2025
  • Revised 23 January 2026
  • Accepted 4 March 2026
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