Flow-stream waveguide for collection of perpendicular light scatter in flow cytometry

Area of Science:

• Fluid dynamics
• Optical physics
• Analytical chemistry

Background:

• Flow cytometry commonly uses microscope objectives for light scatter detection.
• Microscope objectives can be difficult to align and may have suboptimal signal-to-noise ratios.
• Collecting perpendicular light scatter in air presents unique optical challenges.

Purpose of the Study:

• To introduce a new physical configuration for detecting perpendicular light scatter or fluorescence in flow cytometry.
• To enhance the signal-to-noise ratio and reduce the coefficient of variation in flow cytometry measurements.
• To present a simpler and more efficient method for light collection compared to traditional systems.

Main Methods:

• Utilizing the fluid stream in air as a natural optical waveguide.
• Employing a fiber optic with a conically polished tip inserted directly into the flow stream.
• Detecting trapped light scatter using an optical detector connected to the fiber optic.

Main Results:

• Achieved high collection efficiency (NA = 0.88) for perpendicular light scatter.
• Demonstrated a 10-fold increase in signal compared to a long-working-distance microscope objective.
• Observed a narrower coefficient of variation for uniformly sized latex spheres.

Conclusions:

• The flow-stream waveguide configuration offers superior signal-to-noise ratio and precision.
• This technique provides high optical throughput due to minimal interfacial surfaces.
• The method is significantly easier to align than conventional microscope-lens-based systems.