Effects of improved microchannel structures to the separation characteristics of microchip capillary electrophoresis

Microchip electrophoresis (MCE) offers fast and high resolution separation analyses, which have been applied to many fields, particularly in chemical and biological analysis. Many devices for MCE, however, were fabricated with glass and quartz by chemical etching, the fabrication flexibility is restricted because of its isotropically etching property. Moreover, glass fabrication process requires many steps and costs expensive. To overcome these problems, polymers are employed as base materials of microchip and prototyping process using synchrotron radiation (SR) were demonstrated. We have alreadv made a poly-dimethylsilozane (PDMS) microchip by UV lithography. But UV lithography brings the ambiguity of the cross sectional channel structures due to the diffraction effects of incident lights. It seems to change the properties of the channel walls for PDMS chips and causes band broadening of separation. In order to define the channel structure accurately and to investigate its effects to the separation characteristics, we used SR lithography process with thick epoxy negative resist (SU8). The SR has many advantages for the micro fabrication because of its high energy, collimated beam and less diffraction at the microchip channel size region. We used SU-8 as the thick UV/SR resist for the mold of PDMS thermal polymerization.