Fabrication of a micro-channel chip for electrophoresis by using a Photosensitive epoxy resin as an etching mask

In this paper, we present a new fabrication method that uses a UV-sensitive epoxy resin as an etching mask for a micro-channel electrophoresis chip. We have used it to separate fluorescein and fluorescein-5-sulfonic acid. The device was fabricated in a 50mm square of soda glass by using micro-lithographic patterning and wet etching techniques. The proposed method does not need for plating and etching of Au/Cr masks. An etched bottom plate was covered with a top plate drilled access holes into it and permanently bonded in an oven by heating at 560∼580°C. The chip had a separation channel and a sample injection channel. The separation channel was 80μm wide and 20μm deep. Using a micro-fabricated chip with a separation length of 10mm and a separation voltage of 800V, the electrophoresis of a fluorescein and fluorescein-5-sulfonic acid mixture gave two well-separated peaks. Detection was achieved using a laser-induced fluorescence microscope. The HETP of this chip was 3∼4μm for fluorescence samples, and a separation coefficient of 2.2 was realized. The proposed fabrication method is very simple and easy, and has given separation and detection results for fluorescein derivatives.