Smaller scale biological analysis or chemical micro-reactors (e.g. 50 × 25 mm platforms) are being developed in plastics so that smaller samples can be used or sample processing can be carried out more cheaply. Typically these have been made of glass with small fluid channels (～100 microns wide), and sealed with adhesives. In many applications there is a drive to mass produce the units and hence a need for lower cost materials and manufacturing procedures. Use of plastics is being considered widely and joining methods are needed to provide the precision, reproducibility and speed for mass production. Laser welding is well suited to meet these challenges and different processing options have been suggested for the manufacture of these devices. These include using line beam as a curtain of energy over the whole chip either with or without a mask, or by scanning a small spot source around individual channels. The aim is to provide rapid manufacture with high quality and reliability of sealing and in particular without damage to the channels in the units as a result of the welding process. This paper presents results comparing the two main laser welding techniques, line and spot laser sources, and a third short pulse laser in terms of the amount of distortion in the channels after welding and the welding rate and efficiency of processing.
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