A separator system operable to use centrifugation to fractionate a multiple component material, such as a suspension including blood, comprises a buoy. The buoy can be carried in a separation container and has a tuned density that is configured to reach an equilibrium position in the multiple component material. A guide surface is carried on a buoy upper surface and is inclined to an accumulation position near a buoy perimeter. The buoy suspension fractionation system can be used in a method of isolating a fraction from a suspension, and in a method for re-suspending particulates for withdrawal.
