Charge selective membranes/interfaces in microfluidics devices

Charge selective membranes/interfaces in microfluidics devices

Charge selective membranes or interfaces play an important role in membrane technology, such as desalination, separation, electrodialysis and blue energy. To fully understand and optimize these operations at macroscale, high-resolution measurements at small scale are crucial, which is the aim of this research. In systems containing a charge selective interface ion concentration polarization (ICP) is observed under the application of an external electric field, see figure 1 [1]. As a result of this ICP a limiting current regime is observed upon increasing electrical field strength. An overlimiting current can be observed at even higher voltages, indicating an increased flux of ions towards the charge-selective material. Many mechanisms for this increased flux have been proposed (see for instance [2-4]), and thus systematical experimental investigations are important and needed to provide insights into the underlying mechanism. In this assignment we will study the charge flux and flow dynamics of a salt solution adjacent to a charge selective material (for instance a membrane or nanochannel) under an electric field using microfluidics. Different points of focus are possible, e.g.;


Influence of salt concentration (Debye length)


Confinement of microfluidic channels


Influence of inlet flow conditions (flow rate etc.)


Fabrication of an optimal charge-selective interface

Figure 1 - Schematical representation of ICP in systems containing a charge selective material [1]

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1. Kim, S.J., et al., Concentration polarization and nonlinear electrokinetic flow near a nanofluidic channel. Physical Review Letters, 2007. 99(4).

2. Nikonenko, V.V., et al., Intensive current transfer in membrane systems: Modelling, mechanisms and application in electrodialysis. Advances in Colloid and Interface Science, 2010. 160(1-2): p. 101-123.

3. Zangle, T.A., A. Mani, and J.G. Santiago, Theory and experiments of concentration polarization and ion focusing at microchannel and nanochannel interfaces. Chemical Society Reviews, 2010. 39(3): p. 1014-1035.

4. Kim, S.J., Y.-A. Song, and J. Han, Nanofluidic concentration devices for biomolecules utilizing ion concentration polarization: theory, fabrication, and applications. Chemical Society Reviews, 2010. 39(3): p. 912-922.