Steady light transport under flow: characterization of evolving dense random media

Area of Science:

• Physics
• Colloid Science
• Materials Science

Background:

• Understanding the behavior of random media and suspensions is crucial in various scientific fields.
• Characterizing dynamic changes in particle size and organization within emulsions requires advanced measurement techniques.

Purpose of the Study:

• To introduce and validate a novel rheo-optical apparatus for measuring photon transport length (l*) in evolving random media.
• To demonstrate the apparatus's capability in real-time monitoring of emulsion dynamics.

Main Methods:

• Development of a new rheo-optical apparatus to measure photon transport length.
• Validation using stable oil-in-water emulsions with varying droplet sizes and volume fractions.
• Comparison of experimental data with solutions to the diffusion equation and Mie-Percus-Yevick calculations.
• In situ and dynamic study of an oil-in-water emulsification process.

Main Results:

• Successful comparison of apparatus measurements with diffusion equation solutions for emulsion light scattering.
• Validation across a wide range of sample parameters (1% to 64% volume fractions).
• Quantitative agreement between apparatus measurements and independent small-angle light scattering (SALS) data for emulsion dynamics.
• Demonstrated ability to continuously monitor the decrease in average droplet size over time during emulsification.

Conclusions:

• The developed rheo-optical apparatus is effective for measuring photon transport length in evolving random media.
• The system provides accurate, continuous, and non-intrusive monitoring of microscopic and macroscopic flow-induced organization in suspensions.
• This technology offers a valuable tool for studying dynamic processes in emulsions and similar complex fluids.