Capillary Flow-MRI: Quantifying Micron-Scale Cooperativity in Complex Dispersions

Area of Science:

• Fluid Dynamics
• Biophysics
• Materials Science

Background:

• Confined flow of particulate fluids is crucial in applications like 3D printing and cosmetics.
• Predicting cooperative flow in complex fluids requires advanced imaging techniques for optically opaque media.

Purpose of the Study:

• To develop a high-resolution, pressure-driven magnetic resonance imaging (MRI) velocimetry platform for in situ flow analysis of confined complex fluids.
• To quantify cooperative flow phenomena and nonlocal particle interactions in various complex fluid systems.

Main Methods:

• A pressure-driven MRI velocimetry platform was developed using a pressure controller and a capillary with adjustable wall properties and diameter (100-540 μm).
• High spatial resolution (9 μm) enabled quantification of flow cooperativity length scales (ξ) down to 15 μm in Carbopol and fat crystal dispersions (FCD).

Main Results:

• The platform achieved 13% accuracy in quantifying flow cooperativity length scales in Carbopol (particle size d ~ 2 μm).
• For Carbopol, ξ was independent of flow conditions; for FCD, ξ increased with gap size and pressure (0.25-1 bar).
• Nonlocal interactions involved 2-8 particles, with smaller domains dominating at higher confinement.

Conclusions:

• The developed flow-MRI platform is a versatile tool for studying confined complex fluid dynamics.
• The platform's scalability to ultrahigh fields offers potential for chemically resolved velocimetry and applications in 3D printing and in vitro studies.