Doppler optical coherence tomography (DOCT) and traditional OCT techniques can achieve spatial resolution of 1-5 µm.  This is over ten times better than a resolution of an ultrasound. A homemade DOCT device is applied to measure flow velocity profiles of different suspensions from cellular protoplasm to industrial pegments and printable electronics inks.  Flow velocity profile is important for determining rheological characteristics such as a viscosity and a shear rate of non-Newtonian suspensions. The results show that the specificity of the flow profile reconstruction in the case of the flow embedded into the scattering medium is the "non-zero" level of the detected frequencies at the rear border of the capillary.

Additional general information:

1. Doppler optical coherence tomography
2. Optical coherence tomography (OCT) and Doppler optical coherence tomography (DOCT)

Imaging of 1% intralipid flow velocity profile by Doppler OCT.

A time-resolved Doppler OCT image of Physarum strand.
Note the velocity variations and the contractions
of the upper border of the strand wall.