Mapping fast flows over micrometer-length scales using flow-tagging velocimetry and single-molecule detection

Area of Science:

• Fluid dynamics
• Microfluidics
• Analytical chemistry

Background:

• Characterizing microfluidic flow is crucial for understanding fluid behavior in microscale devices.
• Existing methods may lack the resolution or speed to capture complex flow dynamics.

Purpose of the Study:

• To develop and validate a novel technique for high-resolution characterization of microfluidic flow profiles.
• To extend the measurement capabilities to a wide range of flow regimes, including fast near-turbulent flows.

Main Methods:

• Utilized a photo-activated fluorophore and nanosecond laser photolysis for precise temporal triggering.
• Employed high-sensitivity single-molecule detection with Ar+ laser excitation for rapid fluorescence tracking.
• Measured flow speeds up to 47 m/s in a 33-micrometer-wide channel and mapped profiles in a 55-micrometer-wide microchamber.

Main Results:

• Successfully measured and mapped microfluidic velocity profiles across diverse flow regimes.
• Demonstrated the technique's capability for high-resolution 3D flow analysis in micrometer-scale confined spaces.
• Achieved precise measurements despite short time delays (submicrosecond) and fast transit times (as low as 10 ns).

Conclusions:

• The developed technique offers unprecedented capabilities for microfluidic flow characterization.
• Enables detailed analysis of complex flow dynamics in microfluidic devices.
• Has broad applications in scientific research and engineering where precise microscale fluid analysis is required.