Start-Up Electroosmotic Flow of Multi-Layer Immiscible Maxwell Fluids in a Slit Microchannel

Area of Science:

• Fluid Dynamics
• Microfluidics
• Rheology

Background:

• Electroosmotic flow (EOF) is crucial in microfluidic devices.
• Understanding EOF in complex fluids like immiscible viscoelastic fluids is challenging.
• Multi-layer fluid systems introduce intricate interface dynamics.

Purpose of the Study:

• To investigate the transient electroosmotic flow of multi-layer immiscible viscoelastic fluids in a slit microchannel.
• To analyze the influence of electrostatic conditions and rheological properties on flow behavior.
• To determine parameters affecting the transition from transient to steady-state flow.

Main Methods:

• Developed a hyperbolic partial differential equation by combining momentum and Maxwell fluid rheological models.
• Employed the Laplace transform method for semi-analytical solutions.
• Utilized a dimensionless mathematical model to identify key controlling parameters.

Main Results:

• Observed oscillatory velocity profiles in the transient regime due to the interplay of viscous and elastic forces.
• Demonstrated that electrostatic conditions at liquid-liquid interfaces significantly impact the flow field, causing steep velocity gradients.
• Found that relaxation times, viscosity ratios, and the number of fluid layers critically affect the time to reach steady-state.

Conclusions:

• The transient electroosmotic flow of multi-layer immiscible viscoelastic fluids is complex and sensitive to fluid properties and interface conditions.
• Oscillatory behavior is a key characteristic of the transient phase.
• Controlling parameters like relaxation time and viscosity ratios are vital for managing flow dynamics and achieving steady-state.