A low-cost 2D fluorescence detection system for mm sized beads on-chip

In this paper we describe a compact fluorescence detection system for on-chip analysis of beads, comprising a low-cost optical HD-DVD pickup. The complete system consists of a fluorescence detection unit, a control unit and a microfluidic chip containing microchannels and optical markers. With these markers the laser beam of the optical pickup can be automatically focused at the centre of the microchannel. With the complete system a two-dimensional fluorescent profile across the channel width can be obtained such that there is no need for hydrodynamic or electrokinetic focusing of the particles in a specific part of the channel. Fluorescent mm sized beads suspended in medium have been detected with the system. Since on both sides of the main beam two additional laser beams at a known distance are generated, also the velocity of individual beads has been determined.