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Defect-mediated dynamics of coherent structures in active nematics


Active fluids, such as cytoskeletal filaments, bacterial colonies and epithelial cell layers, exhibit distinctive orientational coherence, often characterized by nematic order and its breakdown, defined by the presence of topological defects. In contrast, little is known about positional coherence, that is, whether there is an organization in the underlying fluid motion—despite this being both a prominent and an experimentally accessible feature. Here we characterize the organization of fluid motion in active nematics using the notion of Lagrangian coherent structures by analyzing experimental data of two-dimensional mixtures of microtubules and kinesin, as well as numerical data obtained from the simulation of the active nematodynamic equations. Coherent structures consist of moving attractors and repellers, which orchestrate complex motion. To understand the interaction of positional and orientational coherence, we analyse experiments and simulations and find that +1/2 defects move and deform the attractors, functioning as control centres for collective motion. Additionally, we find that regions around isolated +1/2 defects undergo high bending and low stretching/shearing deformations, consistent with the local stress distribution. The stress is the minimum at the defect, whereas high differential stress along the defect orientation induces folding. Our work offers a new perspective to describe and control self-organization in active fluids, with potential applications to multicellular systems.

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Fig. 1: Lagrangian view of an active nematic fluid.
Fig. 2: Dynamics of a two-dimensional microtubule-based extensile active nematic system assembled on an oil–water interface.
Fig. 3: Dynamics of an extensile active suspension of microtubule bundles and kinesin at an oil–water interface with a 2 μM ATP concentration.
Fig. 4: Lagrangian analysis of a simulated extensile active nematic fluid.
Fig. 5: Stress and deformation around an isolated +1/2 defect in simulated extensile active nematics.

Data availability

The experimental and simulated data that support the findings of this study are available from the corresponding authors upon request.

Code availability

The codes used in this work are available from the corresponding authors upon request.


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We acknowledge T. N. Shendruk, A. Doostmohammadi, K. Thijssen and J. M. Yeomans for providing the dataset29 analysed in Supplementary Fig. 3. We are grateful to S. Shankar and N. Molinari for helpful discussions. This work is partially supported by the Schmidt Science Fellowship and the Postdoc Mobility Fellowship from the Swiss National Foundation (M.S.); the Netherlands Organization for Scientific Research (NWO/OCW) as part of the Frontiers of Nanoscience program and the Vidi scheme (L.G.); the Department of Energy, Office of Basic Energy Sciences, under award no. DESC0019733 (Z.D.); and the NSF Simons Center for Mathematical and Statistical Analysis of Biology via award no. 1764269 (L.M.).

Author information

Authors and Affiliations



M.S. and L.M. designed research, M.S. performed the research. M.S., L.L., L.G., Z.D. and L.M. contributed to the new experimental, numerical and analytical tools. M.S., L.L., L.G., Z.D. and L.M. analysed the data, and M.S. and L.M. wrote the manuscript. All authors commented on the manuscript.

Corresponding authors

Correspondence to Mattia Serra or L. Mahadevan.

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The authors declare no competing interests.

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Nature Physics thanks the anonymous reviewers for their contribution to the peer review of this work

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Supplementary information

Supplementary Information

Supplementary Sections 1–10 and Figs. 1–10.

Supplementary Video 1

Time evolution video associated with Fig. 2a–c.

Supplementary Video 2

Time evolution video associated with Fig. 2d–f.

Supplementary Video 3

Time evolution video associated with Fig. 3.

Supplementary Video 4

Time evolution video associated with Fig. 4.

Supplementary Video 5

Time evolution of defect velocities and backward FTLE field associated with Fig. 4 for increasing T.

Supplementary Video 6

Time evolution of defect velocities and backward FTLE field associated with Fig. 3 for increasing T.

Supplementary Video 7

Time evolution video associated with Supplementary Fig. 4.

Supplementary Video 8

Time evolution video associated with Supplementary Fig. 2.

Supplementary Video 9

Time evolution of defect velocities and backward FTLE field associated with Supplementary Fig. 4 for increasing T.

Supplementary Video 10

Eulerian and Lagrangian analyses of the dancing disclinations flow in confined active nematics (Supplementary Section 6).

Supplementary Video 11

Time evolution video associated with Supplementary Fig. 6.

Supplementary Video 12

Time evolution video associated with Supplementary Fig. 7a.

Supplementary Video 13

Time evolution video associated with Supplementary Fig. 8a,b.

Supplementary Video 14

Time evolution video associated with Supplementary Fig. 8d–i.

Supplementary Video 15

Time evolution video associated with Supplementary Fig. 9a–i.

Supplementary Video 16

Time evolution video associated with Supplementary Fig. 10a–i.

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Serra, M., Lemma, L., Giomi, L. et al. Defect-mediated dynamics of coherent structures in active nematics. Nat. Phys. 19, 1355–1361 (2023).

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