How does particle size affect how quickly particles separate in a centrifuge?

In a centrifuge, the size of a particle significantly influences the speed at which it migrates through a fluid. Larger particles separate more rapidly than smaller ones because the net motivating force—the difference between the centrifugal field and the opposing buoyancy of the liquid—is more effective on them.1

To illustrate the impact of size, all other factors being equal, a particle with a diameter 10 times larger than another requires only 1/100th of the average centrifugal field to travel the same distance in the same amount of time. This relationship is also reflected in the physics of settling; for instance, the terminal velocity of a spherical particle falling through a fluid is proportional to the square of its radius, as described by Stokes’s law.12

Because of these differences in migration rates, centrifuges can be used to achieve partial separation. By controlling the duration of centrifugation, larger particles can be fully packed into the sediment while smaller particles remain suspended in the fluid.1