Integrated 2-D optical lenses designed in PDMS layer to improve fluorescence spectroscopy using optical fibers

In this paper, the fabrication, characterization and test of 2D-optical lenses using PDMS material are reported in order to perform on a portable chip a fluorescence spectroscopy using optical fibers. The technological steps to make the PDMS layer are first detailed, and the patterns then checked with a SEM. By comparing different interfacial structures, it is shown that the light beam characteristics can be modified and slightly focused on the micro-channels where fluorescent dye is flowing. For a constant dye concentration, the use of such lenses enables one to increase the intensity of fluorescent response compared to the same design with a flat interface, which corresponds to a better sensitivity of the detection method.