Ionic effects in self-propelled Pt-coated Janus swimmers

Brown, A. G.; Poon, Wilson

doi:10.1039/c4sm00340c

Cited by 304 publications

(461 citation statements)

References 68 publications

(159 reference statements)

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“…This stresses the role of electrostatics in the system thus discarding neutral diffusiophoresis/osmosis as the main transport mechanism in our system. The importance of electrostatic contributions in the propulsion mechanism of platinum-coated Janus particles has been recently pointed and thoroughly discussed in [43,44].…”

Section: (I) Individual Dynamicsmentioning

confidence: 99%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

128

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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Section: (I) Individual Dynamicsmentioning

confidence: 99%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

128

133

View full text Add to dashboard Cite

show abstract

“…A particular class of active colloids is often connected with these potential applications, namely, artificial selfphoretic colloids [21][22][23][24][25][26][27][28][29]. This is because their fabrication can be well controlled and they appear to be simpler than biological organisms.…”

Section: Introductionmentioning

confidence: 99%

“…Only the total surface reaction rate has been established [21]. However, it has been shown that there is a dependence of the reactivity on the thickness of the Pt-coating [23].…”

Section: Introductionmentioning

confidence: 99%

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The efficiency of self-phoretic propulsion mechanisms with surface reaction heterogeneity

Kreissl

Holm

Graaf

2016

The Journal of Chemical Physics

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We consider the efficiency of self-phoretic colloidal particles (swimmers) as a function of the heterogeneity in the surface reaction rate. The set of fluid, species, and electrostatic continuity equations is solved analytically using a linearization and numerically using a finite-element method. To compare spherical swimmers of different size and with heterogeneous catalytic conversion rates, a 'swimmer efficiency' functional η is introduced. It is proven, that in order to obtain maximum swimmer efficiency the reactivity has to be localized at the pole(s). Our results also shed light on the sensitivity of the propulsion speed to details of the surface reactivity, a property that is notoriously hard to measure. This insight can be utilized in the design of new self-phoretic swimmers.

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“…Active colloids can be induced using photoactive materials [14]. Partially coated colloidal particles with platinum and dispersed in H 2 O 2 solution are often used as model of self-propelled colloids [15]. The motion of an artificial micro-swimmer that uses chemical reaction catallyzed on its own surface to achieve autonomous propulsion is also experimentally possible [16].…”

Section: Introductionmentioning

confidence: 99%

Depletion forces on circular and elliptical obstacles induced by active matter

et al. 2016

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Depletion forces exerted by self-propelled particles on circular and elliptical passive objects are studied using numerical simulations. We show that a bath of active particles can induce repulsive and attractive forces which are sensitive to the shape and orientation of the passive objects (either horizontal or vertical ellipses). The resultant force on the passive objects due to the active particles is studied as a function of the shape and orientation of the passive objects, magnitude of the angular noise, distance between the passive objects. By increasing the distance between obstacles the magnitude of the repulsive depletion force increases, as long as such a distance is less than one active particle diameter. For longer distances, the magnitude of the force always decrease with increasing distance. We also found that attractive forces may arise for vertical ellipses at high enough area fraction.

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Ionic effects in self-propelled Pt-coated Janus swimmers

Cited by 304 publications

References 68 publications

Light-activated self-propelled colloids

Light-activated self-propelled colloids

The efficiency of self-phoretic propulsion mechanisms with surface reaction heterogeneity

Depletion forces on circular and elliptical obstacles induced by active matter

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