A method of particle separation, wherein a collimated light source operable to generate a collimated light source beam is provided. The collimated light source beam includes a beam cross-section. A body is provided, wherein the body defines a wall and a first channel in a first plane. The first channel includes a first channel cross-section, the first channel being oriented to receive the collimated light source beam such that the beam cross-section completely overlaps the channel cross-section. The collimated light source beam is transmitted through the channel. A fluid sample is transmitted through the channel, fluid sample including a plurality of particles of a same type. All of the particles of the plurality of particles are separated axially along the collimated light source beam. All of the particles of the plurality of particles are retained against the wall in the collimated light source beam.