Analysis of DNA fragments by microchip electrophoresis fabricated on poly(methyl methacrylate) substrates using a wire-imprinting method

Microfluidic devices were fabricated on poly(methyl methacrylate) (PMMA) substrate using two small-diameter (79 μm) wires to create a cross impression in plastics softened by low-temperature heating. The resulting channels had a rounded shape and 75 μm in depth. The variability of the channel dimensions was found to be less than 6% from different locations of the same channel and less than 10% between chips. Moreover, the fabricated PMMA chip appeared to sustain an electric field strength up to 300 V/cm without significant Joule heating. The function of resulting devices for electrophoretic injection and separation of a DNA size marker, HaeIII digest of ΦX174, was also characterized. Results indicated that all of the 11 DNA fragments of the size marker could be identified in less than 3 min with relative standard deviations less than 0.4% and 8% for migration time and peak area, respectively. Moreover, with the use of 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 (S/N = 4.2). In conclusion, the performance of wire-imprinted devices on PMMA substrate were comparable to those fabricated by other professional means.