Micro flow cytometers with buried SU-8/SOG optical waveguides

This paper reports an innovative micromachine-based flow cytometer integrated with buried optical waveguides on soda-lime glass substrates. A novel optical waveguide using SU-8/spin-on-glass (SOG) double-layer structure is demonstrated, which increases light guiding efficiency due to smoother channel surface and larger difference of refractive index between SU-8 and organic-based SOG. Instead of using complex optical alignment system, detection light source is coupled with the waveguide with direct insertion of an etched optical fiber. A very high coupling efficiency can be achieved using this approach. In this study, the performance of the waveguides and insertion losses are measured. Experimental results show that the optical loss is less than 15 dB for a 40 mm long waveguide. With the integrated optical waveguides, a micro flow cytometer capable of particle counting has been realized. Data show that microparticles can be hydrodynamically focused and counted successfully without fluorescent labeling using the miniaturized flow cytometer with the integrated optical detection system. (C) 2003 Elsevier Science B.V. All rights reserved.