Diffusion-induced banding of colloid particles via diffusiophoresis

Staffeld, Peter; Quinn, John A.

doi:10.1016/0021-9797(89)90080-5

Cited by 73 publications

(49 citation statements)

References 14 publications

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“…Here it is of interest to compare L D with the thickness of the layer of excess solute L Ψ [2,24] because the latter can be inferred indirectly by measuring the diffusiophoretic speed. It is usually on the order of 10 nm [25]. We find L D = L Ψ = l/2 in the concrete cases of a hard-core repulsion as well as for Ψ(y)/kT = (l/y) n with n → ∞ and small l. Moreover, if one replaces the inner integral limit y in the denominator of Eq.…”

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confidence: 78%

Efficiency of Surface-Driven Motion: Nanoswimmers Beat Microswimmers

Sabass

Seifert

2010

Phys. Rev. Lett.

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Surface interactions provide a class of mechanisms which can be employed for propulsion of microand nanometer sized particles. We investigate the related efficiency of externally and self-propelled swimmers. A general scaling relation is derived showing that only swimmers whose size is comparable to, or smaller than, the interaction range can have appreciable efficiency. An upper bound for efficiency at maximum power is 1/2. Numerical calculations for the case of diffusiophoresis are found to be in good agreement with analytical expressions for the efficiency.

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confidence: 78%

Efficiency of Surface-Driven Motion: Nanoswimmers Beat Microswimmers

Sabass

Seifert

2010

Phys. Rev. Lett.

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“…Instead, diffusiophoretic mobilities have been extracted by measuring particle deposition onto membranes 2,17 and transient migration in stopped-flow fluidic devices. 18 Recent advances in microfluidics, however, have enabled the direct visualization of diffusiophoretic migration, since the small dimensions of microfluidic devices are effective in suppressing buoyancy-driven instabilities. 19 Colloidal streams have been focused and spread using coflowing streams of varying salinity, 20,21 and agarose-based microfluidic devices have been used to drive the diffusiophoretic motion of colloids and DNA under imposed salinity gradients.…”

Section: ■ Introductionmentioning

confidence: 99%

“…22,23 However, these methods have not yet been used to directly measure concentrationdependent diffusiophoretic mobilities, nor to measure the diffusiophoretic migration under nonelectrolyte gradients, which had been predicted theoretically 4,24,25 and verified experimentally. 18 Moreover, only one published report describes colloidal migration under solvent gradients (solvophoresis), 26 based on macroscopic measurements that tracked the turbidity in the vicinity of horizontal interfaces between miscible solutions as it developed over several days. 26 We have recently developed a method to impose local solute and solvent gradients within microchannels, which enabled the first direct microscopic visualization of solvophoretic migration.…”

Section: ■ Introductionmentioning

confidence: 99%

Direct Measurements of Colloidal Solvophoresis under Imposed Solvent and Solute Gradients

et al. 2015

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We describe a microfluidic system that enables direct visualization and measurement of diffusiophoretic migration of colloids in response to imposed solution gradients. Such measurements have proven difficult or impossible in macroscopic systems due to difficulties in establishing solution gradients that are sufficiently strong yet hydrodynamically stable. We validate the system with measurements of the concentration-dependent diffusiophoretic mobility of polystyrene colloids in NaCl gradients, confirming that diffusiophoretic migration velocities are proportional to gradients in the logarithm of electrolyte concentration. We then perform the first direct measurement of the concentration-dependent "solvophoretic" mobility of colloids in ethanol−water gradients, whose dependence on concentration and gradient strength was not known either theoretically or experimentally, but which our measurements reveal to be proportional to the gradient in the logarithm of ethanol mole fraction. Finally, we examine solvophoretic migration under a variety of qualitatively distinct chemical gradients, including solvents that are miscible or have finite solubility with water, an electrolyte for which diffusiophoresis proceeds down concentration gradients (unlike for most electrolytes), and a nonelectrolyte (sugar). Our technique enables the direct characterization of diffusiophoretic mobilities of various colloids under various solvent and solute gradients, analogous to the electrophoretic ζ-potential measurements that are routinely used to characterize suspensions. We anticipate that such measurements will provide the feedback required to test and develop theories for solvophoretic and diffusiophoretic migration and ultimately to the conceptual design and engineering of particles that respond in a desired way to their chemical environments.

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“…1(c)-i], whereas cations diffuse more quickly in KIO 3 and HCl, so that E s points up the gradient [ Fig. 1 On the experimental side, it has been difficult to systematically measure DP mobilities, although methods have been improved from early techniques involving membrane deposition [2] or stop-flow diffusion cells [19] to microfluidic devices made in agarose gels [20]. We have recently developed a microfluidic system that allows systematic and quantitative measurement of DP mobilities [13].…”

Section: Diffusiophoretic Focusing Of Suspended Colloidsmentioning

confidence: 99%