Multi-cell-line micro flow cytometers with buried SU-8/SOG optical waveguides

This paper reports a micro flow cytometer integrated with an innovative buried optical waveguide on soda-lime glass substrates. A novel optical waveguide using SU8/SOG (spin-on-glass) double-layer structure was demonstrated. The light guiding efficiency was improved due to smoother channel surface and larger difference of refractive index between SU-8 and organic-based SOG. Instead of using complicated optical alignment system, detection light source was coupled into the waveguide by directly inserting an etched optical fiber. A very high coupling efficiency could be achieved by this approach. In this study, the performance of the waveguides and insertion losses of the chip were measured. Results showed that the optical loss was less than 15 dB for a 40-mm long waveguide. The buried optical waveguide provides a built-in detection source for cell counting. Preliminary results indicated that a multi-cell-line flow cytometer with built-in detection system could be realized.