Mass transfer and flow in electrically charged micro- and nanochannels

Area of Science:

• Fluid dynamics
• Electrochemistry
• Physical chemistry

Background:

• Electric fields induce fluid flow and mass transfer in channels.
• The electric double layer (EDL) behavior depends on channel dimensions relative to EDL width.

Purpose of the Study:

• To examine fluid flow and mass transfer in rectangular channels under an electric field.
• To investigate microchannel and nanochannel regimes with varying EDL characteristics.
• To analyze symmetric and asymmetric velocity, potential, and mole fraction distributions.

Main Methods:

• Numerical simulations of fluid flow and mass transfer in a rectangular channel.
• Analysis of symmetric and asymmetric distributions for velocity, potential, and mole fraction.
• Comparison with analytical solutions from singular perturbation analysis.
• Consideration of both microchannel and nanochannel regimes.

Main Results:

• Debeye-Huckel and Gouy-Chapman EDL models are recovered at low and high electrolyte concentrations, respectively.
• Symmetric cases show similar velocity and potential fields.
• Asymmetric cases with different wall potentials yield significantly different velocity and potential distributions.
• Volume flow rate varies linearly with channel height for electrically driven flow, unlike pressure-driven flow.

Conclusions:

• Electrically driven flow in channels offers efficient transport, especially in nanochannels.
• Linear dependence of flow rate on channel height facilitates high flow rates at low voltages.
• The study provides insights into electrokinetic phenomena in confined geometries.