This invention is based on size and
mass separation of
suspended particles, including biological matter, which are made to flow in a spiral channel. On the spiral sections, the inward directed
transverse pressure field from
fluid shear competes with the outward directed
centrifugal force to allow for separation of particles. At
high velocity,
centrifugal force dominates and particles move outward. At low velocities,
transverse pressure dominates and the particles move inward. The magnitudes of the two opposing forces depend on flow velocity, particle size,
radius of curvature of the spiral section, channel dimensions, and
viscosity of the fluid. At the end of the spiral channel, a
parallel array of outlets collects separated particles. For any particle size, the required channel dimension is determined by estimating the
transit time to reach the side-wall. This time is a function of flow velocity,
channel width,
viscosity, and
radius of curvature. Larger particles may reach the channel wall earlier than the smaller particles which need more time to reach the side wall. Thus a spiral channel may be envisioned by placing multiple outlets along the channel. This technique is inherently scalable over a
large size range from sub-
millimeter down to 1 μm.