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Measurements of flow-induced birefringence in microfluidics
1Department of Mechanical Engineering, National Taiwan University , Taipei 106, Taiwan.
Biomicrofluidics
|February 10, 2016
Summary
This study introduces a novel microscopic circular polariscope for measuring flow-induced birefringence in microfluidics. This method directly quantifies retardance, enabling real-time stress mapping in microfluidic devices.
Area of Science:
- Fluid Dynamics
- Optical Physics
- Microfluidics
Background:
- Flow-induced birefringence is a phenomenon where fluid motion alters optical properties.
- Previous methods using birefringence microscopy had limitations in real-time quantitation.
- Microfluidic devices are crucial for studying fluid behavior at small scales.
Purpose of the Study:
- To develop and demonstrate a novel method for measuring flow-induced birefringence in microfluidics.
- To enable direct, single-frame, unsteady full-field quantitation of retardance.
- To provide an intuitive, non-invasive visualization of stress in microfluidic flows.
Main Methods:
- Utilized a microscopic circular polariscope for optical measurement.
- Developed a technique for direct retardance measurement from single image frames.
- Correlated retardance with micro-Particle Image Velocimetry (μPIV) data.
Main Results:
- Achieved unsteady full-field quantitation of flow-induced birefringence.
- Found retardance is independent of microfluidic design at low flow rates and proportional to strain rates.
- Demonstrated that both extensional and shear strain rates contribute to birefringence.
Conclusions:
- The developed method offers a non-invasive way to measure fluid stress in microfluidics.
- Retardance distribution directly represents the principal strain rate field.
- This technique facilitates unprecedented real-time stress analysis in microfluidic systems.
