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Published on: August 25, 2016
X-ray photon correlation spectroscopy under flow
Andrei Fluerasu1, Abdellatif Moussaïd, Péter Falus
1Troïka (ID10A) Beamline, European Synchrotron Radiation Facility, Grenoble, France. fluerasu@esrf.fr
X-ray photon correlation spectroscopy reveals how colloidal particles move in shear flow. In transverse flow, particle diffusion is unaffected by flow rate, unlike longitudinal flow where motion is impacted.
Area of Science:
- Soft matter physics
- Colloidal science
- Materials science
Background:
- Understanding particle dynamics in flow is crucial for various applications.
- X-ray photon correlation spectroscopy (XPCS) offers insights into dynamic processes.
- Microfluidics enables controlled environments for studying complex fluid behavior.
Purpose of the Study:
- To investigate the diffusive dynamics of colloidal particles under shear flow using XPCS.
- To explore the influence of scattering geometry on relaxation times in flowing colloidal systems.
- To determine the conditions under which Brownian diffusion can be accurately measured in shear flow.
Main Methods:
- Utilized X-ray photon correlation spectroscopy (XPCS) combined with microfluidic devices.
- Performed experiments with varying shear rates and scattering geometries (transverse and longitudinal flow).
- Analyzed relaxation times derived from XPCS data to probe particle dynamics.
Main Results:
- In a transverse flow geometry (q ⊥ flow), relaxation times were independent of shear rate, reflecting pure Brownian diffusion.
- In a longitudinal flow geometry (q || flow), relaxation times were significantly influenced by flow-induced particle motion.
- Demonstrated that Brownian diffusion of colloidal particles can be measured in flowing samples, particularly at higher scattering vector (q) values.
Conclusions:
- The scattering geometry critically determines whether shear flow affects measured particle dynamics.
- XPCS in microfluidics is a powerful tool for studying colloidal dynamics in flow.
- Optimized experimental conditions, especially higher q values, facilitate the measurement of Brownian diffusion in flowing colloidal systems.
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