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Colloidal inclusions in nematic fluids induce topological defects that govern their dynamics. These defects create well-understood rheological behavior in passive nematics, but the interplay between colloid-associated defects and…

Soft Condensed Matter · Physics 2025-03-26 Timofey Kozhukhov , Benjamin Loewe , Kristian Thijssen , Tyler N. Shendruk

We numerically investigate how spatial variations of extensile or contractile active stress affect bulk active nematic systems in two and three dimensions. In the absence of defects, activity gradients drive flows which re-orient the…

Soft Condensed Matter · Physics 2022-06-15 Liam J Ruske , Julia M Yeomans

Topological defects play a key role in two-dimensional active nematics, and a transient role in two-dimensional active polar fluids. In this paper, we study both the transient and long-time behavior of defects in two-dimensional active…

Soft Condensed Matter · Physics 2020-09-24 Farzan Vafa

We investigate the dynamics of active nematic liquid crystals on deformable membranes, focusing on the interplay between active stress and anisotropic curvature coupling. Using a minimal model, we simulate the coupled evolution of the…

Soft Condensed Matter · Physics 2026-05-19 Yuki Hirota , Nariya Uchida

In pulsating active matter, topological defects are motile despite the absence of any macroscopic flows and microscopic self-propulsion. We reveal that this motility arises from a ratchet effect: the mechanochemical coupling between local…

Soft Condensed Matter · Physics 2026-05-26 Luca Casagrande , Alessandro Manacorda , Etienne Fodor

Non-equilibrium dynamics of topological defects can be used as a fundamental propulsion mechanism in microscopic active matter. Here, we demonstrate swimming of topological defect-propelled colloidal particles in (passive) nematic fluids…

Soft Condensed Matter · Physics 2021-09-30 Tianyi Yao , Žiga Kos , Yimin Luo , Edward B. Steager , Miha Ravnik , Kathleen J. Stebe

We study a continuum model of an extensile active nematic to show that mesoscale turbulence develops in two stages: (i) ordered regions undergo an intrinsic hydrodynamic instability generating walls, lines of stong bend deformations, (ii)…

Soft Condensed Matter · Physics 2015-06-18 Sumesh P. Thampi , Ramin Golestanian , Julia M. Yeomans

Point-like topological defects are singular configurations that occur in a variety of in and out of equilibrium systems with two-dimensional orientational order. As they are associated with a nonzero circuitation condition, the presence of…

Statistical Mechanics · Physics 2023-07-13 Jacopo Romano , Benoît Mahault , Ramin Golestanian

We report on the emergence of stable self-propelled bound defects in monolayers of active nematics, which form virtual full-integer topological defects in the form of vortices and asters. Through numerical simulations and analytical…

Soft Condensed Matter · Physics 2020-10-26 Kristian Thijssen , Amin Doostmohammadi

Geometric confinement and topological constraints present promising means of controlling active materials. By combining analytical arguments derived from the Born-Oppenheimer approximation with numerical simulations, we investigate the…

Soft Condensed Matter · Physics 2023-10-11 Farzan Vafa , David R. Nelson , Amin Doostmohammadi

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…

Soft Condensed Matter · Physics 2026-04-13 Júlio P. A. Santos , Margarida M. Telo da Gama , Rodrigo C. V. Coelho

Active matter is naturally out of equilibrium which results in the emergence of diverse dynamic steady states, including the omnipresent chaotic state known as the active turbulence. However, much less is known how active systems…

Soft Condensed Matter · Physics 2023-04-07 Nika Kralj , Miha Ravnik , Žiga Kos

Confining a liquid crystal imposes topological constraints on the orientational order, allowing global control of equilibrium systems by manipulation of anchoring boundary conditions. In this article, we investigate whether a similar…

The spontaneous emergence of collective flows is a generic property of active fluids and often leads to chaotic flow patterns characterised by swirls, jets, and topological disclinations in their orientation field. However, the ability to…

Soft Condensed Matter · Physics 2017-03-07 Tyler N. Shendruk , Amin Doostmohammadi , Kristian Thijssen , Julia M. Yeomans

The dynamics of active smectic liquid crystals confined on a spherical surface is explored through an active phase field crystal model. Starting from an initially randomly perturbed isotropic phase, several types of topological defects are…

Soft Condensed Matter · Physics 2025-03-11 Michael Nestler , Simon Praetorius , Zhi-Feng Huang , Hartmut Löwen , Axel Voigt

We study the equilibrium shapes of vesicles, with an in-plane nematic order, using a Monte-Carlo scheme and show that highly curved shapes, like tubes and discs, with a striking similarity to the structures engendered by certain curvature…

Biological Physics · Physics 2012-02-16 N. Ramakrishnan , John H. Ipsen , P. B. Sunil Kumar

The self-propulsion of +1/2 topological defects is a hallmark of active nematic fluids, where the defects are advected by the flow field they themselves generate. In this paper we propose a minimal model for defect self-propulsion in a…

Soft Condensed Matter · Physics 2025-08-08 Fridtjof Brauns , Myles O'Leary , Arthur Hernandez , Mark J. Bowick , M. Cristina Marchetti

We study the active flow around isolated defects and the self-propulsion velocity of $+1/2$ defects in an active nematic film with both viscous dissipation (with viscosity $\eta$) and frictional damping $\Gamma$ with a substrate. The…

Soft Condensed Matter · Physics 2022-01-28 Jonas Rønning , M. Cristina Marchetti , Mark J. Bowick , Luiza Angheluta

Morphodynamic equations governing the behaviour of active nematic fluids on deformable curved surfaces are constructed in the large deformation limit. Emphasis is placed on the formulation of objective rates that account for normal…

Soft Condensed Matter · Physics 2023-02-22 Sami C. Al-Izzi , Richard G. Morris

Active matter is characterized by its ability to induce motion by self-generated stress. In the case of a solid, such motion can lead to shape transformations. The stress-generating components can be anisotropic endowing the material with…

Soft Condensed Matter · Physics 2022-05-16 D. J. G. Pearce , S. Gat , G. Livne , A. Bernheim-Groswasser , K. Kruse