Light driven diffusioosmotic repulsion and attraction of colloidal particles

Arya, Pooja; Jelken, Joachim; Lomadze, Nino; Santer, Svetlana

doi:10.1063/5.0007556

Cited by 18 publications

(20 citation statements)

References 35 publications

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“…UV light) one can reversibly switch the state of a suspension of porous particles from a periodic lattice of (separated by distances on the order of tens of micrometres) particles to densely packed surface aggregates (Fig. 2(b, c)) [42]. Note that a similar mechanism of a flow generation near active particles has been reported for calcium carbonate particles [29].…”

Section: Active Particlessupporting

confidence: 54%

Light-induced manipulation of passive and active microparticles

et al. 2021

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We consider sedimented at a solid wall particles that are immersed in water containing small additives of photosensitive ionic surfactants. It is shown that illumination with an appropriate wavelength, a beam intensity profile, shape and size could lead to a variety of dynamic, both unsteady and steady state, configurations of particles. These dynamic, well-controlled and switchable particle patterns at the wall are due to an emerging diffusio-osmotic flow that takes its origin in the adjacent to the wall electrostatic diffuse layer, where the concentration gradients of surfactant are induced by light. The conventional nonporous particles are passive and can move only with already generated flow. However, porous colloids actively participate themselves in the flow generation mechanism at the wall, which also sets their interactions that can be very long ranged. This light-induced diffusio-osmosis opens novel avenues to manipulate colloidal particles and assemble them to various patterns. We show in particular how to create and split optically the confined regions of particles of tunable size and shape, where well-controlled flow-induced forces on the colloids could result in their crystalline packing, formation of dilute lattices of well-separated particles, and other states. Graphic Abstract

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Section: Active Particlessupporting

confidence: 54%

Light-induced manipulation of passive and active microparticles

et al. 2021

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“…Thus, the decay time decreases with increasing intensity (Figure 4c), but the steady state concentration reaches the same values (Figure 4b). The values of k TC and k CT of the polymer-surfactant complex for both wavelengths do not vary significantly with intensity (Figure 4d), as in the case of pure surfactant [28]. We should mention that the photo-isomerization kinetic of the surfactant in a complex with PAA does not depend on the molecular weight of the polymer, as shown for two cases, MW = 0.5.104 g/mol and MW = 25.104 g/mol (see Figure S11 in Supporting Information), since the polyelectrolyte size has a minor influence on the degree of ionization [32].…”

Section: Resultsmentioning

confidence: 76%

“…Thus, the decay time decreases with increasing intensity (Figure 4c), but the steady state concentration reaches the same values (Figure 4b). The values of kTC and kCT of the polymer-surfactant complex for both wavelengths do not vary significantly with intensity (Figure 4d), as in the case of pure surfactant [28]. The kinetic of surfactant photo-isomerization in a complex with PAA (c PAA = 15 wt%) also depends on the intensity of the applied irradiation (Figure 4).…”

Section: Resultsmentioning

confidence: 86%

“…A similar process changes the inter-particle interaction potential in an ensemble of rigid mesoporous colloids, resulting in reversible aggregation or separation of the particles under irradiation with light [27]. Here, when exposed to UV light, the formed cis isomers within the pores readily diffuse out of the particles and generate an excess concentration near the colloids' outer surface, ultimately resulting in the initiation of diffusio-osmotic flow [28][29][30]. The direction of the flow depends strongly on the dynamic redistribution of the fraction of trans and cis isomers near the colloids due to different kinetics of photo-isomerization within the pores as compared to the bulk.…”

Section: Introductionmentioning

confidence: 99%

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Photo-Isomerization Kinetics of Azobenzene Containing Surfactant Conjugated with Polyelectrolyte

et al. 2020

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Ionic complexation of azobenzene-containing surfactants with any type of oppositely charged soft objects allows for making them photo-responsive in terms of their size, shape and surface energy. Investigation of the photo-isomerization kinetic and isomer composition at a photo-stationary state of the photo-sensitive surfactant conjugated with charged objects is a necessary prerequisite for understanding the structural response of photo-sensitive complexes. Here, we report on photo-isomerization kinetics of a photo-sensitive surfactant in the presence of poly(acrylic acid, sodium salt). We show that the photo-isomerization of the azobenzene-containing cationic surfactant is slower in a polymer complex compared to being purely dissolved in aqueous solution. In a photo-stationary state, the ratio between the trans and cis isomers is shifted to a higher trans-isomer concentration for all irradiation wavelengths. This is explained by the formation of surfactant aggregates near the polyelectrolyte chains at concentrations much lower than the bulk critical micelle concentration and inhibition of the photo-isomerization kinetics due to steric hindrance within the densely packed aggregates.

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“…These values of critical micellar concentration agree with literature reports. 34 Above a minimal concentration, the switches form micelles that can solubilize small volumes of the oil droplets into water. This solubilization of oil droplets by the switches modifies the interfacial tension of the droplet locally, at random positions, which leads to symmetry breaking events and ultimately propels the droplet forward.…”

Section: Resultsmentioning

confidence: 99%

Run-and-Halt Behavior of Motile Droplets in Response to Light

Ryabchun¹,

Babu²,

Movilli³

et al. 2021

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We report the run-and-halt behavior of motile droplets immersed in an aqueous solution of amphiphilic molecular switch. These oil droplets move autonomously as the switch solubilizes the oil into the water. Droplet movement stops in response to UV light, and picks up again in response to visible light. This motile behavior is a consequence of the reversible trans-to-cis photo-conversion of the switch in water, because the trans photo-isomer stabilizes the oil droplets better than the cis photo-isomer, and therefore it also solubilizes the droplet more effectively. Notably, the droplets also evolve positive photokinesis under illumination with visible light, and, in patchy light environments, their complex motility pattern directs the droplets at the periphery of the illuminated areas.

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Light driven diffusioosmotic repulsion and attraction of colloidal particles

Cited by 18 publications

References 35 publications

Light-induced manipulation of passive and active microparticles

Light-induced manipulation of passive and active microparticles

Photo-Isomerization Kinetics of Azobenzene Containing Surfactant Conjugated with Polyelectrolyte

Run-and-Halt Behavior of Motile Droplets in Response to Light

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