Refractive Index Measurement with a Flexible OLED-OPD Detection Unit

The refractive index (RI) of liquids plays an important role in chemical analysis and medical diagnostics. Here, we present the integration of a flexible substrate with 6 blue organic light emitting diodes (OLEDs) and 6 organic photodetectors (OPDs) with a flexible microfluidic system formed in polydimethylsiloxane (PDMS). The devices are fabricated by masked thermal evaporation on a $200 \mu \mathrm{m}$ thick polyethylene terephthalate (PET) foil. The individual size of the organic devices is 1 mm x 1 mm. Successful operation of the OLED-OPD matrix for refractive index measurements is demonstrated. This system is intended for RI monitoring of multiple analytes or for analyzing a single analyte with a distributed concentration.