An apparatus for separating particles includes a first planar wall and a spaced apart second planar wall parallel to the first planar wall. The first planar wall and the second planar wall define a passage therebetween, which is disposed along a fluid flow axis. A first plurality of spaced apart elongated ridges extends into the passage from the first planar wall. The first plurality of spaced apart elongated ridges is disposed along a diagonal direction relative to the fluid flow axis. When a fluid is moved through the passage in a direction corresponding to the fluid flow axis, particles of a first type will tend to move in a first direction that is diagonally away from the fluid flow axis and particles of a second type, different from the first type, will tend to move in a second direction that is different from the first direction.
