Publications by Rian Hughes

Collective chemotaxis of active nematic droplets

Physical Review E: Statistical, Nonlinear, and Soft Matter Physics American Physical Society 102 (2020) 020601

R Hughes, J Yeomans

Collective chemotaxis plays a key role in the navigation of cell clusters in e.g. embryogenesis and cancer metastasis. Using the active nematic continuum equations, coupled to a chemical field that regulates activity, we demonstrate and explain a physical mechanism that results in collective chemotaxis. The activity naturally leads to cell polarisation at the cluster interface which induces outwards flows. The chemical gradient then breaks the symmetry of the flow field, leading to a net motion. The velocity is independent of the cluster size in agreement with experiment.

Reconfigurable flows and defect landscape of confined active nematics

Communications Physics Springer Nature 2 (2019) 121

J Hardoüin, R Hughes, A Doostmohammadi, J Laurent, T Lopez-Leon, J Yeomans, J Ignés-Mullol, F Sagués

Using novel micro-printing techniques, we develop a versatile experimental setup that allows us to study how lateral confinement tames the active flows and defect properties of the microtubule/kinesin active nematic system. We demonstrate that the active length scale that determines the self-organization of this system in unconstrained geometries loses its relevance under strong lateral confinement. Dramatic transitions are observed from chaotic to vortex lattices and defect-free unidirectional flows. Defects, which determine the active flow behavior, are created and annihilated on the channel walls rather than in the bulk, and acquire a strong orientational order in narrow channels. Their nucleation is governed by an instability whose wavelength is effectively screened by the channel width. All these results are recovered in simulations, and the comparison highlights the role of boundary conditions.