Autofluorescence of Electrophoresis Chip Grooved by Excimer Laser

The autofluorescence of a chip is a serious problem for high sensitivity optical detection in on-chip electrophoresis. The autofluorescence spectra of a micro channel, which was grooved by an ArF excimer laser on an electrophoresis chip, were measured by a fluorophotometer equipped with a 532nm laser as an excitation source. A commercially available Poly(methylmethacrylate) (PMMA) plate was used as the specimen. The total fluorescence of the laser-grooved micro channel was effectively reduced by optimization of the beam shape, the pulse repetition rate and the traveling speed of the specimen. For further reduction of autofluorescence of the laser grooved micro channel, we used a solvent etching process. When etched by the solvent, the autofluorescence of the grooves was dramatically reduced to a level sufficient for practical electrophoresis. The electrophoresis signals of the chip processed by the combination of laser grooving and solvent etching compared favorably to that of a chip formed by conventional injection molding. The time required to make a micro fluidic chip by this method is only a few hours.