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Nanoscale Dynamics versus Surface Interactions: What Dictates Osmotic Transport?
C Lee1, C Cottin-Bizonne2, R Fulcrand2
1Department of Mechanical Engineering, Kyung Hee University , Yongin 446-701, Korea.
The Journal of Physical Chemistry Letters
|January 10, 2017
Summary
This study challenges traditional osmotic transport understanding by showing membrane-free diffusio-osmosis flows against solute adsorption. Findings offer a generalized framework for osmotically driven flows in nanofluidics.
Area of Science:
- Nanofluidics
- Physical Chemistry
- Surface Science
Background:
- Classical osmotic transport theory links flow direction to solute rejection by semipermeable membranes.
- Diffusio-osmosis, a membrane-free osmotic transport, was previously assumed to follow similar principles.
Purpose of the Study:
- To investigate the direction of diffusio-osmotic flows generated by neutral solutes at silica surfaces.
- To reconcile observed flow directions with solute-surface interactions and near-wall dynamics.
Main Methods:
- Utilized a nanofluidic setup to generate and study diffusio-osmotic flows.
- Employed theoretical and numerical modeling to analyze molecular-scale surface interactions and dynamics.
Main Results:
- Observed that both poly(ethylene)glycol polymers and ethanol generate diffusio-osmotic flows from low to high concentration.
- These flows occurred despite the solutes' tendency to adsorb onto the silica surface, contradicting expectations.
Conclusions:
- Findings necessitate a generalized framework for understanding osmotically driven flows, incorporating surface interactions and near-wall effects.
- Advances understanding of diffusio-osmosis, crucial for fields like energy harvesting and active matter.
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