Micro capillary electrophoresis chips integrated with buried SU-8/SOG optical waveguides for bio-analytical applications

This paper reports an innovative micro electrophoresis chip, which is integrated with buried optical waveguides on glass substrates for on-line detection of bio-analytical samples. A novel buried optical waveguide structure using SU-8/SOG (spin-on-glass) double layers is demonstrated, which can increase light guiding efficiency due to large difference of refractive index between SU-8 (n = 1.8, after hard-baking) and organic-based SOG (n = 1.36). Etched optic fibers are directly inserted into the waveguide channel for connection of light signal between microfluidic devices and peripheral optical sensors. With these novel approaches, delicate optical systems and tedious alignment procedures are not required for biomedical sample detection, resulting in a more compact or even a portable detection system. Experimental results show the developed micro capillary chip can detect Rhodamine B fluoresceins with a concentration as low as 10(-7) M by using multi-mode optic fibers as the connection of light between buried waveguides and the optical sensor. Two samples have been demonstrated to verify the performance of the chip, including a mixture of Rhodamine B and Cy 3 fluorescent dyes and FITC-labeled polypeptide samples. Both of them can be separated and detected successfully using the proposed device. The proposed device provides a cheap and simple method for on-line detection of biological samples. (C) 2003 Elsevier B.V. All rights reserved.