Hydrodynamic Fluctuations and Instabilities in Ordered Suspensions of Self-Propelled Particles

Simha, Robert; Ramaswamy, Sriraṁ

doi:10.1103/physrevlett.89.058101

Cited by 757 publications

(381 citation statements)

References 23 publications

Supporting

Mentioning

347

Contrasting

Unclassified

Order By: Relevance

“…We do not observe experimentally or numerically the swarming behaviour predicted theoretically by many authors [62][63][64][65] for nematic self-propelled particles similar in spirit to the Vicsek model [66]: transition to a flocking behaviour with coherent groups of particles moving in the same direction, swarming or formation of travelling bands otherwise recently observed experimentally by the group of Bausch [67] or more recently the large-scale vortices observed by Sumino et al [68] or by the group of Bartolo with self-propelled rollers colloids [69], or active nematics [70]. In all those works, the self-propelled particles are polar with nematic interactions, i.e.…”

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

confidence: 77%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

131

136

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: 77%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

131

136

View full text Add to dashboard Cite

show abstract

“…Nevertheless, we expect that in the near future novel experiments on the collective motion of selfpropelled rod-shaped colloids will be performed. Aditi Simha and Ramaswamy were the first to study the role of long-range hydrodynamic interactions in the collective motion of swimming force dipoles with polar or nematic order using continuum field theory [351]. The collective motion of hydrodynamically interacting active dumbbells, which are modeled as pairs of point forces, was addressed in [352,353] and later in [354] using dissipative particle dynamics.…”

Section: Microswimmers With Hydrodynamic Interactionsmentioning

confidence: 99%

Emergent behavior in active colloids

Zöttl

Stark

2016

J. Phys.: Condens. Matter

513

559

View full text Add to dashboard Cite

Active colloids are microscopic particles, which self-propel through viscous fluids by converting energy extracted from their environment into directed motion. We first explain how articial microswimmers move forward by generating near-surface flow fields via self-phoresis or the self-induced Marangoni effect. We then discuss generic features of the dynamics of single active colloids in bulk and in confinement, as well as in the presence of gravity, field gradients, and fluid flow. In the third part, we review the emergent collective behavior of active colloidal suspensions focussing on their structural and dynamic properties. After summarizing experimental observations, we give an overview on the progress in modeling collectively moving active colloids. While active Brownian particles are heavily used to study collective dynamics on large scales, more advanced methods are necessary to explore the importance of hydrodynamic and phoretic particle interactions. Finally, the relevant physical approaches to quantify the emergent collective behavior are presented.

show abstract

“…On the single-cell level, attention was given to swarm cell trajectories and the ways in which these trajectories are determined by flagellar motion (8,(21)(22)(23). A combination of experiments (2,3,14,15,(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38) and theory (39)(40)(41)(42)(43) suggests that hydrodynamic interactions play a significant role in this social form of migration.…”

mentioning

confidence: 99%

Periodic Reversals in Paenibacillus dendritiformis Swarming

et al. 2013

View full text Add to dashboard Cite

Bacterial swarming is a type of motility characterized by a rapid and collective migration of bacteria on surfaces. Most swarming species form densely packed dynamic clusters in the form of whirls and jets, in which hundreds of rod-shaped rigid cells move in circular and straight patterns, respectively. Recent studies have suggested that short-range steric interactions may dominate hydrodynamic interactions and that geometrical factors, such as a cell's aspect ratio, play an important role in bacterial swarming. Typically, the aspect ratio for most swarming species is only up to 5, and a detailed understanding of the role of much larger aspect ratios remains an open challenge. Here we study the dynamics of Paenibacillus dendritiformis C morphotype, a very long, hyperflagellated, straight (rigid), rod-shaped bacterium with an aspect ratio of ϳ20. We find that instead of swarming in whirls and jets as observed in most species, including the shorter T morphotype of P. dendritiformis, the C morphotype moves in densely packed straight but thin long lines. Within these lines, all bacteria show periodic reversals, with a typical reversal time of 20 s, which is independent of their neighbors, the initial nutrient level, agar rigidity, surfactant addition, humidity level, temperature, nutrient chemotaxis, oxygen level, illumination intensity or gradient, and cell length. The evolutionary advantage of this unique back-and-forth surface translocation remains unclear. Motile bacteria are able to colonize surfaces using various motility mechanisms (1). One efficient method includes flagellation-based cell motion in conjunction with collective lubrication (typically by secretion of surfactants) to enable fast expansion on hard surfaces. This mode of "bacterial swarming" that has been studied extensively for many species (1-15) enables rapid colony expansion (up to centimeters per hour). Swarming is often marked by hundreds of cells moving in a coordinated fashion while generating whirl and jet patterns.Studies of the collective dynamics of swarming have examined multiple aspects of motility. On the macroscopic level, it was discovered that swarming colonies show an advantage over liquid cultures in that they exhibit an increased resistance to antimicrobials (1,4,5,(15)(16)(17)(18)(19)(20). Studies of collective secretions of signaling and quorum-sensing molecules have shown how interactions between cells in swarming colonies are controlled (11) and exposed the identification of associated genetic manipulations and upregulated proteins that control biosurfactant secretions and flagellar behavior. On the single-cell level, attention was given to swarm cell trajectories and the ways in which these trajectories are determined by flagellar motion (8,(21)(22)(23). A combination of experiments (2, 3, 14, 15, 24-38) and theory (39-43) suggests that hydrodynamic interactions play a significant role in this social form of migration.Hydrodynamic interactions may not always be the dominant physical mechanism controlling bacterial motion....

show abstract

Hydrodynamic Fluctuations and Instabilities in Ordered Suspensions of Self-Propelled Particles

Abstract: We construct the hydrodynamic equations for suspensions of self-propelled particles (SPPs) with spontaneous orientational order, and make a number of striking, testable predictions: (i) SPP suspensions with the symmetry of a true nematic are always absolutely unstable at long

Cited by 757 publications

References 23 publications

Light-activated self-propelled colloids

Light-activated self-propelled colloids

Emergent behavior in active colloids

Periodic Reversals in Paenibacillus dendritiformis Swarming

Contact Info

Product

Resources

About