A poly-methylmethacrylate electrophoresis microchip with sample preconcentrator

A microstructure on poly-methylmethacrylate (PMMA) for sample concentration and electrophoresis was fabricated. This microfabricated structure was able to increase the detection signal and lower the amount of sample used in electrophoretic analysis. The thin-film electrode located at the T-intersection of the sample injection and separation channels provides the current path for the injection channel, but restrains the DNA molecules from passing through. This can accumulate DNA molecules and increase the concentration before performing the electrophoretic analysis. This microstructure was fabricated using krypton fluoride (KrF) excimer laser photo-ablation and fusion bonding techniques. The excimer laser photo-ablation performs rapid prototyping with great flexibility in design changes. The PMMA material is much cheaper than other materials, for example glass and silicon, used in capillary electrophoresis and concentration. The applied electrical field was 300 V cm^-1 for the DNA concentration in this microstructure. Experiments show that the DNA concentration was saturated within 200 s after the DNA molecules first reached the injection tee. The DNA fragments can be concentrated up to five times greater than samples without a concentrator at the injection tee. The separation results also demonstrated that the detected signal intensities of the separated DNA fragments in the tee-type chip with a sample preconcentrator were five times greater than that obtained in a conventional cross-type capillary electrophoresis chip with an identical initial sample concentration.