Method to determine the effective ζ potential in a microchannel with an embedded gate electrode

Area of Science:

• Electrokinetics
• Microfluidics
• Surface Science

Background:

• Microfluidic channels often exhibit non-uniform surface charges due to embedded electrodes.
• Accurate determination of effective zeta potential (ζ(eff)) is critical for controlling fluid behavior in microdevices.
• Existing methods may yield inaccurate results in heterogeneous microchannels.

Purpose of the Study:

• To develop a theoretical model for calculating effective zeta potential (ζ(eff)) in microfluidic channels with tunable surface charges.
• To derive a method for determining ζ(eff) across various salt concentrations using solution displacement.
• To validate the model and method through experimental verification in a heterogeneous microchannel system.

Main Methods:

• Theoretical modeling of effective zeta potential in microchannels with insulated gate electrodes.
• Derivation of a solution displacement technique for ζ(eff) determination.
• Simulation of current-monitoring measurements to identify sources of inaccuracy.
• Experimental validation using a silica-PMDS microchannel with a Ti-Au-Ti gate electrode.

Main Results:

• A theoretical model accurately predicts effective zeta potential (ζ(eff)) in microchannels with non-uniform surface charges.
• The derived method corrects inaccuracies in solution displacement measurements for heterogeneous channels.
• Experimental results with a silica-PMDS system validated the model's predictive capabilities.

Conclusions:

• The developed theoretical model and method provide a reliable tool for predicting effective zeta potential in microfluidic channels with non-uniform zeta potentials.
• This work offers a pathway to accurately characterize and control electrokinetic phenomena in complex microfluidic systems.
• The findings are significant for the design and optimization of microfluidic devices for various applications.