Real-time chemical reaction monitoring in microfluidic environments is demonstrated using luminescent chemical sensors integrated in PDMS/glass-based microscale reactors. A fabrication procedure is presented that allows for straightforward integration of thin polymer layers with optical sensing functionality in microchannels of glass-PDMS chips of only 150 μm width and of 10 to 35 μm height. Sensor layers consisting of polystyrene and an oxygen-sensitive platinum porphyrin probe with film thicknesses of about 0.5 to 4 μm were generated by combining spin coating and abrasion techniques. Optimal coating procedures were developed and evaluated. The chip-integrated sensor layers were calibrated and investigated with respect to stability, reproducibility and response times. These microchips allowed observation of dissolved oxygen concentration in the range of 0 to over 40 mg L(-1) with a detection limit of 368 μg L(-1). The sensor layers were then used for observation of a model reaction, the oxidation of sulphite to sulphate in a microfluidic chemical reactor and could observe sulphite concentrations of less than 200 μM. Real-time on-line monitoring of this chemical reaction was realized at a fluorescence microscope setup with 405 nm LED excitation and CCD camera detection.

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A strength of microfluidic chip laboratories is the rapid heat transfer that, in principle, enables a very homogeneous temperature distribution in chemical processes. In order to exploit this potential, we present an integrated chip system where the temperature is precisely controlled and monitored at the microfluidic channel level. This is realized by integration of a luminescent temperature sensor layer into the fluidic structure together with inkjet-printed micro heating elements. This allows steering of the temperature at the microchannel level and monitoring of the reaction progress simultaneously. A fabrication procedure is presented that allows for straightforward integration of thin polymer layers with optical sensing functionality in microchannels of glass-polydimethylsiloxane (PDMS) chips of only 150 μm width and 29 μm height. Sensor layers consisting of polyacrylonitrile and a temperature-sensitive ruthenium tris-phenanthroline probe with film thicknesses of about 0.5 to 6 μm were generated by combining blade coating and abrasion techniques. Optimal coating procedures were developed and evaluated. The chip-integrated sensor layers were calibrated and investigated with respect to stability, reproducibility, and response times. These microchips allowed observation of temperature in a wide range with a signal change of around 1.6 % per K and a maximum resolution of around 0.07 K. The device is employed to study temperature-controlled continuous micro flow reactions. This is demonstrated exemplarily for the tryptic cleavage of coumarin-modified peptides via fluorescence detection.

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