Hydrodynamic capture of microswimmers into sphere-bound orbits

Takagi, Daisuke; Palacci, Jérémie; Braunschweig, Adam B.; Shelley, Michael; Zhang, Jun

doi:10.1039/c3sm52815d

Cited by 236 publications

(258 citation statements)

References 38 publications

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“…Since the results presented in Figs. 3(a),(b) relate higher v x with smaller η, and smaller a or larger D, our findings indicate that cluster formation around the obstacles is essential for the occurrence of rectification (particle current) [8,32]. The drift velocity increases with increasing D (and decreasing a).…”

Section: B Half-circular Obstaclementioning

confidence: 63%

“…In our model, we do not consider hydrodynamic interactions (which is believed to be responsible for the motions observed in Ref. 32), which could force the disks to attach to the solid surfaces. In fact, we observed that a single swimmer trajectory in a lattice of half-circles differs little qualitatively from a trajectory realized in a lattice of circles with the same initial conditions.…”

Section: A Arrays Of Symmetric and Asymmetric Obstaclesmentioning

confidence: 99%

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Self-propelled particle transport in regular arrays of rigid asymmetric obstacles

2014

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We report numerical results which show the achievement of net transport of self-propelled particles (SPP) in the presence of a two-dimensional regular array of convex, either symmetric or asymmetric, rigid obstacles. The repulsive inter-particle (soft disks) and particle-obstacle interactions present no alignment rule. We find that SPP present a vortex-type motion around convex symmetric obstacles even in the absence of hydrodynamic effects. Such a motion is not observed for a single SPP, but is a consequence of the collective motion of SPP around the obstacles. An steady particle current is spontaneously established in an array of non-symmetric convex obstacle (which presents no cavity in which particles may be trapped in), and in the absence of an external field. Our results are mainly a consequence of the tendency of the self-propelled particles to attach to solid surfaces.

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Section: B Half-circular Obstaclementioning

confidence: 63%

Section: A Arrays Of Symmetric and Asymmetric Obstaclesmentioning

confidence: 99%

Self-propelled particle transport in regular arrays of rigid asymmetric obstacles

2014

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“…2(c) shows the predicted average lifetimes corresponding to the best fit value for the phenomenological parameter α. It has been shown recently that artificial microswimmers can be captured into sphere-bound orbits by colloidal particles of fixed size [39]. The existence of a critical size for trapping of dipolar swimmers around spherical colloids was recently theoretically predicted by using far-field hydrodynamics [38].…”

Section: H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

Hydrodynamic Trapping of Swimming Bacteria by Convex Walls

et al. 2015

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Swimming bacteria display a remarkable tendency to move along flat surfaces for prolonged times. This behavior may have a biological importance but can also be exploited by using microfabricated structures to manipulate bacteria. The main physical mechanism behind the surface entrapment of swimming bacteria is, however, still an open question. By studying the swimming motion of Escherichia coli cells near microfabricated pillars of variable size, we show that cell entrapment is also present for convex walls of sufficiently low curvature. Entrapment is, however, markedly reduced below a characteristic radius. Using a simple hydrodynamic model, we predict that trapped cells swim at a finite angle with the wall and a precise relation exists between the swimming angle at a flat wall and the critical radius of curvature for entrapment. Both predictions are quantitatively verified by experimental data. Our results demonstrate that the main mechanism for wall entrapment is hydrodynamic in nature and show the possibility of inhibiting cell adhesion, and thus biofilm formation, using convex features of appropriate curvature. DOI: 10.1103/PhysRevLett.114.258104 PACS numbers: 47.63.Gd, 87.17.Jj, 87.18.Ed Self-propelled bacteria living in aqueous media have constant, vivid interactions with their local environment, which may dramatically alter their swimming behavior [1][2][3][4][5][6][7][8]. Often, bacterial habitats are physically confined by solid boundaries. Physical interactions with these solid surfaces give rise to a rich variety of dynamical phenomena like steering or rectification of swimming direction [9] and the propulsion of microfabricated structures [10]. Understanding the physical mechanisms behind cell-surface interactions is of crucial importance to design structures that could fully exploit those effects for microfluidic applications. On the other hand, a quantitative understanding of wall entrapment and subsequent adhesion would allow us to design surfaces that hinder unwanted biological processes like biofilm formation. Surface colonization by biofilm-forming bacteria is initiated by cell contact and adhesion to the surface [11][12][13]. The subsequent biofilm growth can cause highly resistant bacterial infections on medical implants and catheters or impaired industrial equipment [14][15][16][17][18][19].Using a tracking microscope, Frymier et al. observed that bacteria display a marked tendency to swim adjacent to wall surfaces [20]. At the beginning, this behavior was attributed to an attractive interaction potential between the cell body and the solid surface. It was later proposed, however, that, while DLVO forces could be responsible for irreversible adhesion, wall entrapment during swimming may have a purely hydrodynamic origin [21,22]. Hydrodynamic effects can indeed give rise to wall entrapment via two distinct mechanisms. The first one is via farfield, dipolar flows that, once reflected by a flat wall, give rise to reorientation parallel to the wall surface as well as an attraction by the wa...

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“…Active matter exhibits a wealth of non-equilibrium effects observed in nature as well as synthetic systems: pattern formation [12,13], enhanced mixing [14,15] or sensing and interaction with the environment. For example, Escherichia coli bacteria were shown to concentrate owing to the presence of microfluidic funnels [16], rotate microscopic gears [17,18] or self-propelled nanorods are captured by passive spheres, stressing the importance of activity-driven interactions [19]. From a fundamental standpoint, they allow for the development of a theoretical framework for non-equilibrium statistical mechanics [20].…”

Section: Introductionmentioning

confidence: 99%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

130

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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Hydrodynamic capture of microswimmers into sphere-bound orbits

Cited by 236 publications

References 38 publications

Self-propelled particle transport in regular arrays of rigid asymmetric obstacles

Self-propelled particle transport in regular arrays of rigid asymmetric obstacles

Hydrodynamic Trapping of Swimming Bacteria by Convex Walls

Light-activated self-propelled colloids

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