Emergence of macroscopic directed motion in populations of motile colloids

By A. Bricard, Jean-Baptiste Caussin, N. Desreumaux, O. Dauchot, Denis Bartolo. Nature, 2013

892 citations recorded by the source corpus.

From the formation of animal flocks to the emergence of coordinated motion in bacterial swarms, populations of motile organisms at all scales display coherent collective motion. This consistent behaviour strongly contrasts with the difference in communication abilities between the individuals. On the basis of this universal feature, it has been proposed that alignment rules at the individual level could solely account for the emergence of unidirectional motion at the group level. This hypothesis has been supported by agent-based simulations. However, more complex collective behaviours have been systematically found in experiments, including the formation of vortices, fluctuating swarms, clustering and swirling. All these (living and man-made) model systems (bacteria, biofilaments and molecular motors, shaken grains and reactive colloids) predominantly rely on actual collisions to generate collective motion. As a result, the potential local alignment rules are entangled with more complex, and often unknown, interactions. The large-scale behaviour of the populations therefore strongly depends on these uncontrolled microscopic couplings, which are extremely challenging to measure and describe theoretically. Here we report that dilute populations of millions of colloidal rolling particles self-organize to achieve coherent motion in a unique direction, with very few density and velocity fluctuations. Quantitatively identifying the microscopic interactions between the rollers allows a theoretical description of this polar-liquid state. Comparison of the theory with experiment suggests that hydrodynamic interactions promote the emergence of collective motion either in the form of a single macroscopic ‘flock’, at low densities, or in that of a homogenous polar phase, at higher densities. Furthermore, hydrodynamics protects the polar-liquid state from the giant density fluctuations that were hitherto considered the hallmark of populations of self-propelled particles. Our experiments demonstrate that genuine physical interactions at the individual level are sufficient to set homogeneous active populations into stable directed motion.

Subfields: Biomedical Engineering, Condensed Matter Physics, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/ae8b0086f1d52fd9b53b831bdc0abc5f1f1fa9c6

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Biomedical Engineering

In Condensed Matter Physics

In Mechanical Engineering

Citations in the corpus

The statistical physics of active matter: From self-catalytic colloids to living cells (2017, background): “Importantly, this theoreticalworkwill need experimental validation,which is becoming available thanks to the development of ingenious man-made realization of active systems where controlled experiments are possible [3,105].”
Topological active matter (2020, background): “Active ordered fluids have been assembled from a variety of soft materials 5–7, 55 , 56 .”
Flow interactions lead to orderly formations of flapping wings in forward flight (2016, background): “From an engineering perspective, such systems represent many-body fluid-structure interactions, and our understanding of these could lead to applications such as novel materials composed of active microparticles [8], arrangements of propulsors for air or water vehicles [9], and devices that harvest ”
Geometry and topology of turbulence in active nematics (2014, background): “The paradigm of “active matter” [1–3] has had notable successes over the past decade in describing selforganization in a surprisingly broad class of biological and bioinspired systems: from flocks of starlings [4,5] to robots [6], down to bacterial colonies [7–11], motile colloids [12,13], and the c”
Entropy production in field theories without time reversal symmetry: Quantifying the non-equilibrium character of active matter (2016, background): “[6] Antoine Bricard, Jean-Baptiste Caussin, Nicolas Desreumaux, Olivier Dauchot, and Denis Bartolo, “Emergence of macroscopic directed motion in populations of motile colloids,” Nature 503, 95–98 (2013).”
A phase diagram for bacterial swarming (2019, background): “…rods [Peruani 2006; Ginelli 2010; Wensink 2012; Abkenar 2013; Shi 2018, Jeckel 2019, Bär 2019] and experiments with artificial inanimate systems [Narayan 2007, Kudrolli 2008, Bricard 2013], the swarming phase diagram has several unique characteristics that are not observed in other active systems.”
Selective and collective actuation in active solids (2021, neutral): “This dynamical and chiral phase, which is reminiscent of oscillations in biological tissues 15,24 , is clearly different from collective dynamics in active fluids 35,36 and rigid body motion in active solids 3,5,9 .”
Symmetry, Thermodynamics, and Topology in Active Matter (2021, background): “[26] Antoine Bricard, Jean-Baptiste Caussin, Nicolas Desreumaux, Olivier Dauchot, and Denis Bartolo, “Emergence of macroscopic directed motion in populations of motile colloids,” Nature 503, 95–98 (2013).”
Minimal model of active colloids highlights the role of mechanical interactions in controlling the emergent behavior of active matter (2015, background): “These include autophoretic colloids [5, 6, 17], rollers [18], and droplets [19].”
Pressure is not a state function for generic active fluids (2014, methodology): “These well-established models have been used [5, 7, 23– 27] to describe respectively active colloids [6, 8, 21, 22], or bacterial motion [4, 27] and cell migration [28].”