Light Activated Self-Propelled Colloids

Abstract

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 (αFe2 O3 and TiO2 ), 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 self- propulsion 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.

Invited Contribution to a theme issue of Phil. Trans. Soc. A: "New trends in active liquid crystals: mechanics, dynamics and applications"

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Cited by in corpus (37)

• Emergent behavior in active colloids
• Statistical Mechanics of Active Ornstein Uhlenbeck Particles
• Odd Viscosity and Odd Elasticity
• An active approach to colloidal self-assembly
• Light-induced self-assembly of active rectification devices
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• Active turbulence in active nematics
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• Slip length dependent propulsion speed of catalytic colloidal swimmers near walls
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• Three-body problem for Langevin dynamics with different temperatures
• Reconfiguration, Interrupted Aging and Enhanced Dynamics of a Colloidal Gel using Photo-Switchable Active Doping
• Colloidal Brazil nut effect in microswimmer mixtures induced by motility contrast
• Self-avoidant memory effects on enhanced diffusion in a stochastic model of environmentally responsive swimming droplets
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• Designing active colloidal folders
• Quantifying the non-equilibrium activity of an active colloid
• On the effect of boundaries on noninteracting weakly active particles in different geometries
• Dynamical response of a system of passive or active swimmers to time-periodic forcing
• Density-Independent transient caging in the high-density phase of motility-induced phase separation
• Programmable Persistent Random Walks in Active Brownian Particles Govern Emergent Dynamics
• The effect of self-induced Marangoni flow on polar-nematic waves in active-matter systems