Diffusion layer formation drives zone migration in travelling wave electrophoresis

Area of Science:

• Analytical Chemistry
• Chemical Engineering
• Biophysics

Background:

• Microfluidic devices offer precise control over chemical and biological processes.
• Electrophoresis is a key technique for separating charged species.
• Traveling-wave electrophoresis (TWE) presents a novel approach for manipulation of charged particles.

Purpose of the Study:

• To simulate and analyze 2D traveling-wave electrophoresis for microfluidic separations and sample concentration.
• To investigate the influence of electric wave parameters on charged particle transport.
• To validate the simulation model against experimental observations.

Main Methods:

• Utilized COMSOL finite element modeling software for 2D simulations.
• Applied a four-phase AC potential to a periodic interdigitated four-electrode array.
• Incorporated a simplified model of asymmetric electrode reactions to address electric double layer shielding.
• Modeled selective reactions to form diffusion layers of charged particles.

Main Results:

• The simulation successfully reproduced experimental separations of charged species based on their electrophoretic mobilities.
• Demonstrated that charged particles are transported by the traveling electric wave, with separation dependent on mobility.
• Showcased the formation of diffusion layers that dictate charged species transport.
• Verified the role of electrode reactions in enabling particle manipulation.

Conclusions:

• Traveling-wave electrophoresis is a viable method for microfluidic separations and sample concentration.
• The simulation model accurately predicts the behavior of charged particles in TWE systems.
• Control over frequency and direction of the electric wave allows for tunable separation and concentration of charged particles.