Microfabricated plastic chips by hot embossing methods and their applications for DNA separation and detection

Design and fabrication of microfluidic devices on polymethylmethacrylate (PMMA) substrates for analytical chemistry and biomedical-related applications using novel microfabrication methods are described. The image of microstructures is transferred from quartz master templates possessing the inverse image of the devices to plastic plates by using hot embossing methods. The microchannels on quartz master templates are formed by the combination of metal etch mask and wet chemical etching of a photomask blank. The micromachined quartz templates can be used repeatedly to replicate cheap and disposable plastic devices. The reproducibility of the hot embossing method is evaluated using 10 channels on different PMMA plastics. The relative standard deviation of the channel profile on the plastic chips is less than 1%. In this study, the PMMA microfluidic chips have been demonstrated as a microcapillary electrophoresis (μ-CE) device for DNA separation and detection. The capability of the fabricated chip for electrophoretic injection and separation is characterized via the analysis of DNA fragments ∅X-174-RF HaeIII digest. Experimental results indicate that all of the 11 DNA fragments of the size marker could be identified in less than 2 min with relative standard deviations less than 0.4 and 8% for migration time and peak area, respectively. Moreover, with the use of a near-infrared (IR) dye, fluorescence signals of the higher molecular weight fragments (>603 bp in length) could be detected at total DNA concentrations as low as 0.1 μg/ml. In addition to DNA fragments ∅X-174-RF HaeIII digest, DNA sizing of hepatitis C viral (HCV) amplicon is also achieved using microchip electrophoresis on PMMA substrates.