Micro-flow analysis by molecular tagging velocimetry and planar Raman-scattering.

Area of Science:

• Microfluidics
• Fluid Dynamics
• Optical Measurement Techniques

Background:

• Traditional microfluidic velocimetry often relies on micro-particle imaging, which can have limitations.
• Accurate measurement of velocity and concentration fields is crucial for understanding microfluidic mixing processes.

Purpose of the Study:

• To develop and validate a novel optical flow technique for two dimensional molecular tagging velocimetry (2D-MTV).
• To measure spatial concentration fields in microflows using Planar Spontaneous Raman Scattering (PSRS).
• To assess the accuracy of the developed 2D-MTV method by comparison with micro-Particle Image Velocimetry (μPIV).

Main Methods:

• Generated arbitrary flow patterns using a caged dye and mask imaging, tracked by laser-induced fluorescence.
• Analyzed image sequences with a novel optical flow-based quantitative technique.
• Employed spectrally selective filtering in Planar Spontaneous Raman Scattering (PSRS) for species-specific concentration measurements.

Main Results:

• The 2D-MTV technique demonstrated accurate velocity field measurements in microfluidic flows.
• Reference measurements and comparison with μPIV confirmed the procedure's accuracy.
• Successful spatial concentration measurements were achieved for a water-ethanol mixture using PSRS.

Conclusions:

• The novel optical flow-based 2D-MTV offers a robust method for microfluidic velocimetry.
• The developed PSRS technique enables accurate spatial concentration measurements in microflows.
• These advancements provide powerful tools for analyzing complex microfluidic phenomena.