Hydrodynamic and entropic effects on colloidal diffusion in corrugated channels

In the absence of advection, confined diffusion characterizes transport in many natural and artificial devices, such as ionic channels, zeolites, and nanopores. While extensive theoretical and numerical studies on this subject have produced many important predictions, experimental verifications of t...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2017-09, Vol.114 (36), p.9564-9569
Main Authors: Yang, Xiang, Liu, Chang, Li, Yunyun, Marchesoni, Fabio, Hänggi, Peter, Zhang, H. P.
Format: Article
Language:English
Subjects:
Brownian motion
Channels
Computer simulation
Diffusion
Diffusion effects
Diffusivity
Fluid mechanics
Impact analysis
Mathematical models
Microchannels
Neck
Numerical analysis
Physical Sciences
Porosity
Studies
Transport
Zeolites
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Summary:In the absence of advection, confined diffusion characterizes transport in many natural and artificial devices, such as ionic channels, zeolites, and nanopores. While extensive theoretical and numerical studies on this subject have produced many important predictions, experimental verifications of the predictions are rare. Here, we experimentally measure colloidal diffusion times in microchannels with periodically varying width and contrast results with predictions from the Fick–Jacobs theory and Brownian dynamics simulation. While the theory and simulation correctly predict the entropic effect of the varying channel width, they fail to account for hydrodynamic effects, which include both an overall decrease and a spatial variation of diffusivity in channels. Neglecting such hydrodynamic effects, the theory and simulation underestimate the mean and standard deviation of first passage times by 40% in channels with a neck width twice the particle diameter. We further show that the validity of the Fick–Jacobs theory can be restored by reformulating it in terms of the experimentally measured diffusivity. Our work thus shows that hydrodynamic effects play a key role in diffusive transport through narrow channels and should be included in theoretical and numerical models.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1707815114