Nonstationary electroosmotic flow in closed cylindrical capillaries

Area of Science:

• Physics
• Fluid Dynamics
• Electrochemistry

Background:

• Electroosmotic flow (EOF) is crucial in microfluidic devices.
• Understanding fluid behavior in closed systems under electrical fields is complex.
• Previous models often focused on open capillaries or simpler voltage inputs.

Purpose of the Study:

• To develop a theoretical model for EOF and hydrodynamic flow in wide closed cylindrical capillaries subjected to stepwise voltage.
• To derive analytical expressions for flow dynamics under various periodic and aperiodic voltage regimes.
• To analyze the impact of voltage pulse parameters on liquid velocity profiles and displacement.

Main Methods:

• Development of a theoretical model for EOF and hydrodynamic flow.
• Derivation of analytical expressions for direct and backflow.
• Numerical analysis of liquid velocity profiles and displacement for different voltage regimes (periodic and aperiodic).
• Comparison of results with those from open capillaries.

Main Results:

• Analytical expressions for EOF and hydrodynamic flow were obtained as a sum of direct and backflow solutions.
• Numerical analysis revealed qualitative peculiarities in liquid velocity profiles and displacement based on the number and type of voltage pulses.
• Distinct flow behaviors were observed in closed versus open capillaries.

Conclusions:

• The developed theoretical model accurately describes EOF and hydrodynamic flow in closed capillaries under stepwise voltage.
• The study highlights the influence of voltage pulse characteristics on fluid dynamics.
• The findings suggest that aperiodic stepwise voltage regimes can be effectively utilized for investigating electrophoresis.