Brownian and advective dynamics in microflow studied by coherent X-ray scattering experiments

Area of Science:

• Physics
• Materials Science
• Chemical Engineering

Background:

• Studying the structure and dynamics of flowing samples is crucial for understanding complex fluids.
• Traditional methods often struggle to capture both structural and dynamic information simultaneously in microfluidic systems.

Purpose of the Study:

• To demonstrate the combined power of microfluidics and coherent X-ray illumination for analyzing colloidal suspension dynamics.
• To characterize advective and Brownian motion in microflows of varying geometries.
• To evaluate sample structure and detailed flow behavior in a single experiment.

Main Methods:

• Utilizing an experimental setup with a fast two-dimensional detector.
• Performing X-ray correlation spectroscopy by calculating 2D maps of intensity auto-correlation functions.
• Scanning a microfocused X-ray beam across microfluidic devices with different channel geometries (straight, curved, constricted).

Main Results:

• Successfully evaluated sample structure and characterized detailed flow behavior, including flow geometry, main flow directions, and advective flow velocities.
• Quantified diffusive dynamics alongside flow patterns.
• Mapped anisotropic auto-correlation functions of driven colloidal suspensions with high spatial resolution.

Conclusions:

• The combined microfluidics and X-ray scattering approach is powerful for studying complex fluid dynamics.
• This method offers significant potential for analyzing flow patterns in complex fluids and characterizing anisotropic dynamics in materials.