Particle separation and collection using an optical chromatographic filter

An optofluidic design has been used to completely separate and collect fractions of an injected mixture of colloidal particles. A three-dimensional glass microfluidic device was constructed such that the fluid was directed though a 50 - μ m -diameter channel. A laser was introduced opposite the flow and its spot size adjusted to completely fill the channel. Thus, for a given laser power and flow rate, certain particles are completely retained while others pass through unhindered. Separation efficiencies in excess of 99% have been attained for a mixture of polymer and silica beads.