Detection of small particles in fluid flow using a self-mixing laser

Area of Science:

• Fluid dynamics
• Optical velocimetry
• Laser physics

Background:

• Accurate detection and measurement of small particles in fluid flow are crucial for various scientific and industrial applications.
• Traditional methods may lack sensitivity, real-time capabilities, or require complex setups.
• Laser Doppler velocimetry (LDV) offers a non-intrusive approach but can be improved for detecting lower concentrations and smaller particles.

Purpose of the Study:

• To develop and demonstrate a highly sensitive, real-time method for detecting small particles in fluid flow.
• To utilize self-mixing laser Doppler measurement with a specialized laser for enhanced optical sensitivity.
• To validate the system's ability to measure fluid flow characteristics and particle properties.

Main Methods:

• Employed a laser-diode-pumped, thin-slice solid-state laser for self-mixing laser Doppler velocimetry.
• Analyzed asymmetric power spectra of laser output modulated by re-injected scattered light from particles.
• Used a small-diameter glass pipe for fluid flow experiments with dilute samples.

Main Results:

• Observed asymmetric power spectra that accurately reflect the fluid flow velocity distribution, obeying Poiseuille's law.
• Successfully performed rapid measurements of flow rate and kinetic viscosities for water-glycerol mixtures.
• Achieved measurable low-concentration detection limits below 1 ppm for 262-nm polystyrene latex spheres and below 10 ppm for 3-μm red blood cells.

Conclusions:

• The developed self-mixing laser Doppler velocimeter system provides a highly sensitive and real-time method for particle detection in fluid flow.
• The system demonstrates capability in characterizing fluid dynamics and measuring low concentrations of microparticles.
• This technique holds promise for applications requiring precise monitoring of particle behavior in various fluid systems.