Concentration polarization at microfluidic-nanofluidic interfaces
Abstract/Contents
- Abstract
- Nanofluidic devices have the potential to offer unique functionality by exploiting length scales comparable to the Debye length or the size of individual biomolecules. Integration of nanofluidics with microfluidics also has potential benefits as a system can thereby draw from the benefits of both technologies. To leverage these functionalities, the physics associated with interfacing microchannels and nanochannels needs to be understood rigorously. In particular, when current is applied across a microchannel-nanochannel interface, surface charge effects inside the nanochannel often lead to an imbalance of fluxes of positive and negative species. This, in turn, creates a region of high ionic strength on one side of the nanochannel and low ionic strength on the other side, a phenomena known as concentration polarization (CP). Prior work on the physics of microchannel-nanochannel interfaces has neglected several key issues which we will address in this work. We review an analytical model of propagating CP and present experimental and computational validation of this model. In particular, our results show that enrichment and depletion regions propagate as 'shockwaves' of concentration which can profoundly change the flow and electric field conditions in a microfluidic system. Additionally, we present new analytical model which predicts the behavior of analyte ions in a microchannel-nanochannel system with CP. This work shows that CP can restrict the transport of analyte ions such that they cannot reach all regions of a microfluidic-nanofluidic system. The effects of CP, therefore, must be considered in the design of microfluidic-nanofluidic systems for biological or chemical analysis. Finally we present the first simultaneous visualization of nanochannel ionic strength and conductance. Our experiments show that, for some cases, the propagating CP model is a fair predictor of trends in nanochannel concentration. However, in some cases, the concentration inside the nanochannel reaches a temporary 'meso' state before transitioning to a final, significantly different concentration which is not described by theory. The latter shows that there is yet much room for further studies of this phenomenon.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Zangle, Thomas Andrew |
|---|---|
| Associated with | Stanford University, Department of Mechanical Engineering |
| Primary advisor | Santiago, Juan G |
| Thesis advisor | Santiago, Juan G |
| Thesis advisor | Eaton, John K |
| Thesis advisor | Howe, Roger Thomas |
| Advisor | Eaton, John K |
| Advisor | Howe, Roger Thomas |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Thomas A. Zangle. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2010. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2010 by Thomas Andrew Zangle
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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