Eppur si muove, and yet it moves: Patchy (phoretic) swimmers

Aubret, Antoine; Ramananarivo, Sophie; Palacci, Jérémie

doi:10.1016/j.cocis.2017.05.007

Cited by 41 publications

(49 citation statements)

References 137 publications

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“…In the following, we devise swimmers with a fore-aft asymmetry, consisting of the extrusion of the haematite cube from a chemically inert polymer bead 24 (Supplementary Information). In uniform light, they exhibit a persistent random walk as previously reported for Janus microswimmers 11,25 . The polymer bead heads and the velocity, up to 30 μ m s −1 , is controlled by the light intensity.…”

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confidence: 53%

Targeted assembly and synchronization of self-spinning microgears

et al. 2018

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Self-assembly is the autonomous organization of components into patterns or structures: an essential ingredient of biology and a desired route to complex organization 1 . At equilibrium, the structure is encoded through specific interactions 2-8 , at an unfavourable entropic cost for the system. An alternative approach, widely used by nature, uses energy input to bypass the entropy bottleneck and develop features otherwise impossible at equilibrium The self-assembly of complex structures which emulate the fidelity and tunability of their biological counterparts is a fundamental goal of materials science and engineering. In colloidal science, the paradigm for equilibrium self-assembly encodes information through specific interactions between building blocks that, in turn, promote assembly, so that the resulting (static) structure is the thermodynamic ground state. Emergent properties in active matter 13

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confidence: 53%

Targeted assembly and synchronization of self-spinning microgears

et al. 2018

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“…Among artificial swimmers, catalytically active particles constitute a large and important class [15][16][17]. These particles typically move by self-phoresis, i.e., by consuming molecular 'fuel'-available in the surrounding…”

Section: Introductionmentioning

confidence: 99%

Shape-dependent guidance of active Janus particles by chemically patterned surfaces

et al. 2018

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Self-phoretic chemically active Janus particles move by inducing-via non-equilibrium chemical reactions occurring on their surfaces-changes in the chemical composition of the solution in which they are immersed. This process leads to gradients in chemical composition along the surface of the particle, as well as along any nearby boundaries, including solid walls. Chemical gradients along a wall can give rise to chemi-osmosis, i.e., the gradients drive surface flows which, in turn, drive flow in the volume of the solution. This bulk flow couples back to the particle, and thus contributes to its selfmotility. Since chemi-osmosis strongly depends on the molecular interactions between the diffusing molecular species and the wall, the response flow induced and experienced by a particle encodes information about any chemical patterning of the wall. Here, we extend previous studies on selfphoresis of a sphere near a chemically patterned wall to the case of particles with rod-like, elongated shape. We focus our analysis on the new phenomenology potentially emerging from the couplingwhich is inoperative for a spherical shape-of the elongated particle to the strain rate tensor of the chemi-osmotic flow. Via detailed numerical calculations, we show that the dynamics of a rod-like particle exhibits a novel 'edge-following' steady state: the particle translates along the edge of a chemical step at a steady distance from the step and with a steady orientation. Moreover, within a certain range of system parameters, the edge-following state co-exists with a 'docking' state (the particle stops at the step, oriented perpendicular to the step edge), i.e., a bistable dynamics occurs. These findings are rationalized as a consequence of the competition between the fluid vorticity and the rate of strain by using analytical theory based on the point-particle approximation which captures quasi-quantitatively the dynamics of the system.

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“…Such pH-gradients are utilized by many artificial swimmers for propulsion and steering of collective behaviors. Examples include catalytic particles [4,23,40,41] or swimmers responding to an external pH-gradients, i.e. performing pH taxis [42,43].…”

Section: Introductionmentioning

confidence: 99%

Large scale micro-photometry for high resolution pH-characterization during electro-osmotic pumping and modular micro-swimming

et al. 2017

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Micro-fluidic pumps as well as artificial micro-swimmers are conveniently realized exploiting phoretic solvent flows based on local gradients of temperature, electrolyte concentration or pH. We here present a facile micro-photometric method for monitoring pH gradients and demonstrate its performance and scope on different experimental situations including an electro-osmotic pump and modular micro-swimmers assembled from ion exchange resin beads and polystyrene colloids. In combination with the present microscope and DSLR camera our method offers a 2 μm spatial resolution at video frame rate over a field of view of 3920×2602 μm 2 . Under optimal conditions we achieve a pH-resolution of 0.05 with about equal contributions from statistical and systematical uncertainties. Our quantitative micro-photometric characterization of pH gradients which develop in time and reach out several mm is anticipated to provide valuable input for reliable modeling and simulations of a large variety of complex flow situations involving pH-gradients including artificial micro-swimmers, microfluidic pumping or even electro-convection.

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Eppur si muove, and yet it moves: Patchy (phoretic) swimmers

Cited by 41 publications

References 137 publications

Targeted assembly and synchronization of self-spinning microgears

Targeted assembly and synchronization of self-spinning microgears

Shape-dependent guidance of active Janus particles by chemically patterned surfaces

Large scale micro-photometry for high resolution pH-characterization during electro-osmotic pumping and modular micro-swimming

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