R ectangular channels for lab - on - a - chip applications

We investigated the application of two technologies for the fabrication of rectangular microchannels with reasonable path lengths for UV detection in UV transparent materials. The first approach uses inductively coupled plasma (ICP)–reactive ion etching (RIE) to fabricate channels in fused silica wafers, using a 4-mm-thick nickel layer as protective mask. The effects of the process parameters on the etched channel profile and surface quality were studied directly using electron scanning microscopy, and indirectly through capillary electrophoresis experiments. In the second approach, narrow channels were easily realized in poly(dimethylsiloxane) (PDMS) using replica molding and dry-etched silicon masters. UV absorbance detection of tryptophan was possible vertically through these PDMS channels, using pre-aligned optical fibers to guide light to the channel and collect and bring the transmitted light to the detector.  2003 Elsevier Science B.V. All rights reserved.