Sub-diffusion flow velocimetry with number fluctuation optical coherence tomography

We have implemented number fluctuation dynamic light scattering optical coher-ence tomography (OCT) for measuring extremely slow, sub-diffusion flows of dilute particle suspensions using the second-order autocovariance function. Our method has a lower mini-mum measurable velocity than conventional correlation-based OCT or phase-resolved Doppler OCT, as the velocity estimation is not affected by the particle diffusion. Similar to non-dilute correlation-based OCT, our technique works for any Doppler angle. With our analysis we can quantitatively determine the concentration of particles under flow. Finally, we demonstrate 2D sub-diffusion flow imaging with a scanning OCT system at high rate by performing number fluctuation correlation analysis on subsequent B-scans.

Automated summary

We have developed a number fluctuation dynamic light scattering optical coherence tomography (OCT) technique to measure slow flows of dilute particle suspensions. Our method overcomes the limitations of conventional correlation-based OCT and provides more accurate velocity estimation. It can also determine the concentration of particles under flow and enables 2D sub-diffusion flow imaging using a scanning OCT system.