Why do substances form separate layers at different radii in a density-gradient centrifuge?

In a density-gradient centrifuge, substances form separate layers at different radii because the instrument utilizes a pre-established radial density variation, often created using nonreactive molecules like sucrose or calcium chloride.1

When a mixture is subjected to a centrifugal field within this gradient, each substance migrates through the medium until it reaches a position where its own particle density matches the density of the surrounding gradient. Once a substance reaches this point of equilibrium, it collects in a thin cylindrical layer at that specific radius. If a solution contains multiple substances, each will settle at a distinct radius determined by its unique particle density, effectively separating the components based on their buoyancy within the gradient.1