Flow field-flow fractionation (AF4) channel cross section, where the rate of laminar flow within the channel is not uniform. It travels in a parabolic pattern with the speed of the flow, increasing towards the centre of the channel and decreasing towards the sides.
Centrifugal FFF separates by mass (i.e. a combination of particle density and particle size). For example, gold and silver nanoparticles of identical size can be separated into two peaks, according to differences in density of gold and silver.