Collective Motion of Vibrated Polar Disks

Deseigne, Julien; Dauchot, Olivier; Chaté, Hugues

doi:10.1103/physrevlett.105.098001

Cited by 540 publications

(591 citation statements)

References 34 publications

Supporting

Mentioning

575

Contrasting

Unclassified

Order By: Relevance

“…they align their velocity vectors in direction, as prescribed by 'Vicsek's rule'. The role of the nematic alignment owing to the collisions of rod-like microtubules have recently been pointed by [68] to explain the emergence of long-range interactions and vortices at high density (or in an granular context by Deseigne et al [71]). In our experiment, owing to the isotropic shape of the particles we do not observe any nematic interaction of the self-propelled particles, thus defining a different class of systems and non-equilibrium phases than the Vicsek model.…”

Section: (D) Living Crystals Versus Swarming and Flocks Behaviourmentioning

confidence: 99%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

131

133

View full text Add to dashboard Cite

Light-activated self-propelled colloids are synthesized and their active motion is studied using optical microscopy. We propose a versatile route using different photoactive materials, and demonstrate a multiwavelength activation and propulsion. Thanks to the photoelectrochemical properties of two semiconductor materials (α-Fe 2 O 3 and TiO 2 ), a light with an energy higher than the bandgap triggers the reaction of decomposition of hydrogen peroxide and produces a chemical cloud around the particle. It induces a phoretic attraction with neighbouring colloids as well as an osmotic selfpropulsion of the particle on the substrate. We use these mechanisms to form colloidal cargos as well as self-propelled particles where the light-activated component is embedded into a dielectric sphere. The particles are self-propelled along a direction otherwise randomized by thermal fluctuations, and exhibit a persistent random walk. For sufficient surface density, the particles spontaneously form 'living crystals' which are mobile, break apart and reform. Steering the particle with an external magnetic field, we show that the formation of the dense phase results from the collisions heads-on of the particles. This effect is intrinsically non-equilibrium and a novel principle of organization for systems without detailed balance. Engineering families of particles self-propelled by different wavelength demonstrate a good understanding of both the physics and the chemistry behind the system and points to a general route for designing new families of self-propelled particles.

show abstract

Section: (D) Living Crystals Versus Swarming and Flocks Behaviourmentioning

confidence: 99%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

131

133

View full text Add to dashboard Cite

show abstract

“…This hypothesis has been supported by agent-based simulations 1,5,6 . However, more complex collective behaviors have been systematically found in experiments including the formation of vortices 7-9 , fluctuating swarms 7, 10 , clustering 11,12 , and swirling [13][14][15][16] . All these (living and man-made) model systems (bacteria 9,10, 16 , biofilaments and molecular motors 7,8,13 , shaken grains 14, 15 and reactive colloids 11,12 ) predominantly rely on actual collisions to display collective motion.…”

mentioning

confidence: 99%

Emergence of macroscopic directed motion in populations of motile colloids

Bricard¹,

Caussin²,

Desreumaux³

et al. 2013

Nature

Self Cite

889

1,029

View full text Add to dashboard Cite

From the formation of animal flocks to the emergence of coordinate motion in bacterial swarms, at all scales, populations of motile organisms display coherent collective motion.This consistent behavior strongly contrasts with the difference in communication abilities between the individuals. Guided by this universal feature, physicists have proposed that solely alignment rules at the individual level could account for the emergence of unidirectional motion at the group level [1][2][3][4] . This hypothesis has been supported by agent-based simulations 1,5,6 . However, more complex collective behaviors have been systematically found in experiments including the formation of vortices 7-9 , fluctuating swarms 7, 10 , clustering 11,12 , and swirling [13][14][15][16] . All these (living and man-made) model systems (bacteria 9,10, 16 , biofilaments and molecular motors 7,8,13 , shaken grains 14, 15 and reactive colloids 11,12 ) predominantly rely on actual collisions to display 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 that are extremely challenging to measure and describe theoretically.Here, we demonstrate a new phase of active matter. We reveal that dilute populations of millions of colloidal rollers self-organize to achieve coherent motion along a unique direction, with very few density and velocity fluctuations. Identifying, quantitatively, 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, which were hitherto considered as the hallmark of populations of self-propelled particles 2, 3, 17 . Our experiments demonstrate that genuine physical interactions at the individual level are sufficient to set homogeneous active populations into stable directed motion.Our system consists of large populations of colloids capable of self-propulsion and of sensing the orientation of their neighbors solely by means of physical mechanisms. We take advantage of an overlooked electrohydrodynamic phenomenon referred to as the Quincke rotation 18,19 (Fig. 1a).When an electric field E 0 is applied to an insulating sphere immersed in a conducting fluid, above a critical field amplitude E Q , the charge distribution at the sphere's surface is unstable to infinitesimal fluctuations. This spontaneous symmetry breaking results in a net electrostatic torque, which causes the sphere to rotate at a constant speed around a random direction transverse to E 0 18 . We 2 exploit this instability to engineer self-propelled colloidal rollers. We use ...

show abstract

“…Experiments have begun to achieve the extraordinary capabilities and emergent properties of these biological systems in nonliving active fluids of self-propelled particles, consisting of chemically [7][8][9][10][11][12] or electrically [13] propelled colloids, or monolayers of vibrated granular particles [14][15][16].…”

mentioning

confidence: 99%

Dynamics of self-propelled particles under strong confinement

2014

View full text Add to dashboard Cite

We develop a statistical theory for the dynamics of non-aligning, non-interacting self-propelled particles confined in a convex box in two dimensions. We find that when the size of the box is small compared to the persistence length of a particle's trajectory (strong confinement), the steady-state density is zero in the bulk and proportional to the local curvature on the boundary. Conversely, the theory may be used to construct the box shape that yields any desired density distribution on the boundary. When the curvature variations are small, we also predict the distribution of orientations at the boundary and the exponential decay of pressure as a function of box size recently observed in 3D simulations in a spherical box.Active fluids consisting of self-propelled units are found in biology on scales ranging from the dynamically reconfigurable cell cytoskeleton [1] to swarming bacterial colonies [2,3], healing tissues [4,5], and flocking animals [6]. Experiments have begun to achieve the extraordinary capabilities and emergent properties of these biological systems in nonliving active fluids of self-propelled particles, consisting of chemically [7][8][9][10][11][12] or electrically [13] propelled colloids, or monolayers of vibrated granular particles [14][15][16].In contrast to thermal motion, active motion is correlated over experimentally accessible time and length scales. When the persistence length of active motion becomes comparable to the mean free path, uniquely active effects arise that transcend the thermodynamically allowed behaviors of equilibrium systems, including giant number fluctuations and spontaneous flow [3,14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Importantly, a sufficient active persistence length is the only requirement for macroscopic manifestations of activity, as revealed by athermal phase separation of nonaligning, repulsive self-propelled particles [31][32][33][34][35][36][37][38][39][40][41].When boundaries and obstacles are patterned on the scale of the active correlation length, they dramatically alter the dynamics of the system, and striking macroscopic properties emerge [42][43][44][45][46][47][48][49]; for example, ratchets and funnels drive spontaneous flow in active fluids [42][43][44][45][46]. This effect has been used to direct bacterial motion [50] and harness bacterial power to propel microscopic gears [51][52][53]. However, optimizing such devices for technological applications requires understanding the interaction of an active fluid with boundaries of arbitrary shape. More generally, any real-world device necessarily includes boundaries, and thus the effects of boundary size and shape are essential design parameters. Although recent studies have explored confinement in simple geometries [43,47,[54][55][56], there is no general theory for the effect of boundary shape.In this Letter, we study the dynamics of non-aligning and non-interacting self-propelled particles confined to two-dimensional convex containers, such as ellipses and polygons. We find...

show abstract

Collective Motion of Vibrated Polar Disks

Cited by 540 publications

References 34 publications

Light-activated self-propelled colloids

Light-activated self-propelled colloids

Emergence of macroscopic directed motion in populations of motile colloids

Dynamics of self-propelled particles under strong confinement

Contact Info

Product

Resources

About