Poly（dimethylsiloxane） Microchips with Two Sharpened Stretching Tips and Its Application to Protein Separation Using Dynamic Coating

An integrated poly（dirnethylsiloxane） （PDMS） microchip with two sharpened stretching tips for convenient sample injecting, running buffer refreshing and channel cleaning has been presented. The sample was directly introduced into the separation channel through the stretching inlet tip without complicated power switching supplies and injection cross channel. The operation of running buffer refreshing or channel cleaning was simplified by vacuuming one end of the tip and placing the other tip into the solution vial. Therefore, this fabrication method can be easily applied to most analytical laboratories economically without soft lithography and plasma bonding equipments. The attractive performance of the novel PDMS microchips has been demonstrated by using laser-induced fluorescence detection for separation of proteins. The addition of 0.04% Brij 35 in 0.04 mol/L phosphate buffer （pH 7.0） can reduce the adhesion of proteins in multienzyme tablet and make separation more easily. The electroosmotic flow （EOF） exhibits pH-independence in the range of 3-1 1 in dynamic modified microchannel.