4.4.   4l Miniaturized RIfS Sensor

The second setup, which is based on RIfS as detection principle, is shown in figure 13. This so-called 4l system bases on a wavelength separation in the light source. Individual wavelengths are sequentially emitted by 4 light emitting diodes rendering a spectral recording of the reflected light unnecessary. Thus, the reflected light is detected by a simple photodiode enabling a miniaturization of the system and a reduction of the costs. The setup, which has been used for the detection of single analytes and sum parameters, is described elsewhere in detail [178],[179]. As the parallelization of this setup is still in progress, the measurements using two different sensitive layers were performed in series.

figure 13:  Schematic of the 4l setup. The yellow bubble shows the reconstruction of the shifted interference pattern after the sorption of analyte into the polymer layer (green before sorption of analyte, magenta after sorption of analyte).