Three-dimensional visualization and analysis of flowing droplets in microchannels using real-time quantitative phase...

Area of Science:

• Microfluidics
• Optical Microscopy
• Biomedical Engineering

Background:

• Droplet-based microfluidics are vital for high-throughput analysis across various scientific fields.
• Existing methods for inspecting flowing droplets lack real-time, label-free, and 3-D capabilities.
• There is a need for advanced imaging techniques to overcome these limitations in microfluidic analysis.

Purpose of the Study:

• To develop and demonstrate a real-time quantitative phase microscopy (RT-QPM) technique for 3-D droplet visualization.
• To enable label-free, full-field measurement of analyte concentration within flowing droplets.
• To provide a robust method for analyzing droplet dynamics and composition in microchannels.

Main Methods:

• Utilized a linear-CCD-based holographic microscopy configuration with an optofluidic phase-shifting element.
• Implemented RT-QPM for retrieving quantitative phase maps of microfluidic droplets at high temporal resolution.
• Experimentally validated 3-D image reconstruction and quantitative analysis of droplets in different flow regimes.

Main Results:

• Successfully achieved 3-D image reconstruction of droplets in squeezing and dripping regimes.
• Quantitatively analyzed droplet volume, morphology, and depth-related parameters under varying flow conditions.
• Demonstrated the RT-QPM technique as a refractive index sensor for in-line carbamide concentration measurement.

Conclusions:

• RT-QPM is an effective tool for label-free, real-time 3-D visualization and analysis of microfluidic droplets.
• The technique offers precise characterization of droplet dynamics and enables quantitative analyte concentration measurements.
• This advancement holds significant potential for applications in biological, chemical, and environmental high-throughput analyses.