Viscous Wave Breaking and Ligament Formation in Microfluidic Systems.

Area of Science:

• Fluid dynamics
• Microfluidics
• Hydrodynamic stability

Background:

• Mixing and emulsification in microsystems rely on hydrodynamic instabilities.
• Large viscosity differences between fluids present challenges in microfluidic applications.

Purpose of the Study:

• To experimentally investigate the stability of high-viscosity fluid stratifications in microchannels.
• To characterize interfacial wave dynamics, including breaking and viscous ligament entrainment.
• To explore the role of inflectional instabilities in stratified microflows.

Main Methods:

• Experiments were conducted in square microchannels using miscible and immiscible fluid pairs.
• Characterization of interfacial wave propagation dynamics.
• Analysis of fluid velocities and viscosity contrasts.

Main Results:

• Novel viscous wave regimes were identified.
• Dispersion relationships were determined with and without interfacial tension.
• Optimal conditions for passive disturbance and dispersion of fluids were found.

Conclusions:

• Understanding hydrodynamic instabilities is key for efficient microfluidic mixing.
• Viscous wave dynamics offer insights into fluid dispersion mechanisms.
• This research provides a basis for optimizing microfluidic devices for handling diverse fluid viscosities.