Laser induced fluorescence photobleaching anemometer for microfluidic devices

Area of Science:

• Microfluidics
• Fluid Dynamics
• Optical Measurement Techniques

Background:

• Accurate fluid velocity measurement is crucial for microfluidic device characterization and optimization.
• Existing methods can be intrusive or complex, limiting their application.
• Photobleaching of fluorescent dyes offers a potential basis for novel sensing modalities.

Purpose of the Study:

• To develop and validate a novel, non-intrusive method for measuring fluid velocity in microfluidic devices.
• To establish a relationship between fluorescence intensity changes due to photobleaching and fluid flow velocity.
• To demonstrate the method's applicability to different flow types within microfluidic systems.

Main Methods:

• Utilized photobleaching of a fluorescent dye within a laser beam to assess fluid velocity.
• Measured the residence time of the dye in the laser beam, correlating it with fluorescence decay.
• Developed a calibration curve relating fluorescence intensity to known flow velocities for quantitative analysis.

Main Results:

• Demonstrated an inverse relationship between dye residence time and fluid velocity.
• Showed that fluorescence intensity increases with flow velocity due to decreased residence time.
• Successfully applied the method to measure velocities in both pressure-driven and electroosmotic flows.

Conclusions:

• The developed photobleaching-based method provides a rapid and user-friendly approach for non-intrusive fluid velocity measurement in microfluidics.
• The technique is versatile and applicable to various microfluidic flow regimes.
• This method offers a valuable tool for real-time monitoring and characterization of microfluidic systems.