Athermal Phase Separation of Self-Propelled Particles with No Alignment

Very small synthetic motors that use chemical reactions to drive their motion are being studied widely because of their potential applications, which often involve active transport and dynamics on nanoscales. Like biological molecular machines, they must be able to perform their tasks in complex, highly fluctuating environments that can form chemical patterns with diverse structures. Motors in such systems can actively assemble into dynamic clusters and other unique nonequilibrium states. It is shown how chemical patterns with small characteristic dimensions may be utilized to suppress rotational Brownian motions of motors and guide them to move along prescribed paths, properties that can be exploited in applications. In systems with larger pattern length scales, domains can serve as catch basins for motors through chemotactic effects. The resulting collective motor dynamics in such confining domains can be used to explore new aspects of active particle collective dynamics or promote specific types of active self‐assembly. More generally, when chemically self‐propelled motors operate in far‐from‐equilibrium active chemical media the variety of possible phenomena and the scope of their potential applications are substantially increased.

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“…Simple active Brownian particle models are able to capture some aspects of this dynamics 50, 51, 52, 53, 54…”

Section: Resultsmentioning

confidence: 99%

Chemically Propelled Motors Navigate Chemical Patterns

Chen

Kapral

2018

Advanced Science

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“…This behaviour arises from a self-trapping mechanism: self-propelled particles with a persistent time and colliding head on, arrest each other owing to the persistence of their orientation (figure 6a). Increasing the surface fraction of particles, this simple mechanism leads to a dynamic phase transition from a gas phase of hot colloids [10] to a dense state, resulting from the 'traffic jam' of the persistent self-propelled particles [46,[50][51][52][53][54][55][56][57]. The emergence of arrested phase owing to density-dependent mobility has been discussed theoretically in the context of bacteria by Tailleur & Cates [58].…”

Section: (C) Results and Discussionmentioning

confidence: 99%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

131

133

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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.

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“…The dynamics of a homogeneous fluid of self-propelled particles has been described by an effective continuum theory where motility suppression is incorporated in a density-dependent propulsion speed v(ρ) 12,15,16,34 . The mean-field model applies when particles experience many collisions before their directed motion becomes uncorrelated by rotational noise, i.e., for ζ >> 1 26 .…”

Section: A Mean-field Theory and Phase Separationmentioning

confidence: 99%

Freezing and phase separation of self-propelled disks

2014

Self Cite

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We study numerically a model of non-aligning self-propelled particles interacting through steric repulsion, which was recently shown to exhibit active phase separation in two dimensions in the absence of any attractive interaction or breaking of the orientational symmetry. We construct a phase diagram in terms of activity and packing fraction and identify three distinct regimes: a homogeneous liquid with anomalous cluster size distribution, a phase-separated state both at high and at low density, and a frozen phase. We provide a physical interpretation of the various regimes and develop scaling arguments for the boundaries separating them.

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Athermal Phase Separation of Self-Propelled Particles with No Alignment

Cited by 1,082 publications

References 38 publications

Chemically Propelled Motors Navigate Chemical Patterns

Chemically Propelled Motors Navigate Chemical Patterns

Light-activated self-propelled colloids

Freezing and phase separation of self-propelled disks

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