Quantifying Brownian motion in the presence of simple shear flow with particle diffusometry

Area of Science:

• Fluid dynamics
• Biotechnology
• Analytical chemistry

Background:

• Particle diffusometry quantifies Brownian motion to determine diffusion coefficients.
• Current limitations include inaccurate measurements at elevated temperatures and fluid flow.
• These limitations restrict its application in dynamic biological and chemical systems.

Purpose of the Study:

• To enhance particle diffusometry for use in simple shear flow and at various temperatures.
• To develop a correction equation for accurate diffusion coefficient measurements under flow and thermal conditions.
• To expand the applicability of particle diffusometry in real-world scenarios.

Main Methods:

• Simulated Brownian motion videos under varying flow and temperature conditions.
• Developed a modified particle diffusometry algorithm with a correction equation for shear flow (three polynomial degrees).
• Validated the algorithm through experiments in a rectangular channel with controlled fluid flow.

Main Results:

• The modified algorithm accurately computes diffusion coefficients with less than 10% error at flow rates up to 8 units.
• Successfully applied particle diffusometry across a temperature range of 25-65°C.
• Experimental validation confirmed simulation findings, demonstrating algorithm robustness.

Conclusions:

• The updated particle diffusometry method overcomes previous temperature and flow limitations.
• This advancement broadens the potential applications of particle diffusometry, particularly in pathogen detection and fluid analysis.
• The developed correction equation enables reliable measurements in dynamic fluid environments.