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Electric-field-controlled flow in nanoscale-thin wetting films
Jairus Kleinert1, Sejong Kim, Orlin D Velev
1Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|December 27, 2011
Summary
Researchers developed a new nanofluidic system using electroosmotic flow in thin water films on mica. This simple, low-cost system enables controlled fluid movement at the nanoscale.
Area of Science:
- Nanotechnology
- Physical Chemistry
- Fluid Dynamics
Background:
- Electroosmotic flow (EOF) is crucial for micro/nanofluidic devices.
- Controlling fluid behavior in nanoscale thin films presents unique challenges.
- Existing nanofluidic fabrication methods can be complex and expensive.
Purpose of the Study:
- To report a novel nanofluidic system utilizing EOF in nanoscale aqueous wetting films.
- To investigate the formation and characteristics of these thin water films on mica substrates.
- To demonstrate a simple and cost-effective method for fabricating nanofluidic confinement.
Main Methods:
- Formation of spontaneous aqueous wetting films on mica substrates under saturated humidity.
- Optical interference and fluorescence intensity measurements to determine film thickness.
- Application of a DC electric field for inducing lateral flow and tracking fluorescent probes.
- Microcontact printing of hydrophobic monolayers to create 2D confinement channels.
Main Results:
- Water films with thicknesses of a few tens of nanometers were formed.
- Film thickness was consistent with theoretical predictions balancing electrostatic repulsion and capillary pressure.
- Lateral flow was successfully induced and characterized by probe movement.
- Observed fluid and probe mobilities were lower than electrokinetic theory predictions, possibly due to probe adsorption.
Conclusions:
- A novel, simple, and inexpensive nanofluidic system based on EOF in wetting films was successfully developed.
- The system allows for controlled fluid manipulation at the nanoscale within confined 2D channels.
- This approach offers a cost-effective alternative to traditional lithography-based nanofluidic device fabrication.
