Two-beam cross-correlation:  a method to characterize transport phenomena in micrometer-sized structures

Area of Science:

• Physics
• Chemistry
• Biotechnology

Background:

• Accurate characterization of fluid dynamics in microstructured channels is crucial for applications like capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC).
• Traditional methods for measuring microflow properties can be time-consuming or lack the required spatial resolution.

Purpose of the Study:

• To develop and validate an experimental method for determining flow velocity and angle in microstructured channels.
• To enable simultaneous measurement of diffusion properties of single molecules.

Main Methods:

• Utilized fluorescence correlation spectroscopy (FCS) with two micrometer-sized, spatially separated volume elements.
• Recorded and mathematically evaluated the cross-correlation signal between these elements.
• Implemented a two-beam cross-correlation approach for enhanced data acquisition.

Main Results:

• Achieved fast and easy determination of flow velocities as low as 200 μm/s.
• Enabled simultaneous measurement of diffusion properties with a detection time of 5-100 s and <20% error.
• Obtained vectorial flow data with spatial resolution of 1-2 μm.

Conclusions:

• The developed two-beam cross-correlation FCS method offers a precise, simple, and fast approach for microflow analysis.
• This technique has significant potential for applications in CE, HPLC, chemical kinetics, and high-throughput screening.