Microfabricated electrophoresis chips on quartz substrates and their applications on DNA analysis

Design and fabrication of micro capillary electrophoresis (CE) chips on quartz substrates are described. The micro capillary channels are formed by the combination of a metal etch mask and wet chemical etching. In this paper, a simple but reliable one-mask process is applied to fabricate micro structures on quartz substrates, which are commercially-available blank photomasks. The selection of the quartz substrates greatly simplifies the fabrication process. The substrates with micro channels are then bonded with another quartz cover plate at low temperature by using diluted hydrofluoric acid (HF) solution. Good channel sealing is observed. The low temperature bonding yields low residual stress and makes chemical surface modification prior to bonding feasible, if necessary. The quartz chips with higher UV transmittance allow us to use a laser induced fluorescence detection system for chemical analysis successfully. Solutions containing Nile blue are first performed in the CE chips as a demonstration of electrophoretic injection. The capability of the microfabricated CE chips for electrophoretic injection and separation is then characterized via the analysis of DNA fragments φX174 digested by Hae III. An excellent signal/noise ratio is obtained. In addition to single-channel sample injection and separation, multi-channel devices capable of parallel electro-migration of multi-samples have also been demonstrated in the study.