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J Baena, N. Kaun, S. Kulka, J. Frank, P. Svasek, D Moss, B. Lendl:
"Synchrotron IR Monitoring of Chemical Events in Microfluidic Mixing Devices and CE Microchips";
Poster: 1^st BASIE Workshop, Karlsruhe (Germany); 11.09.2003 - 12.09.2003.

This presentation deals with the design of dedicated micro-machined devices to perform basic chemical operational units such us mixing and electrophoretic separation using in-chip mid-IR detection. On the one hand, a fast and highly reproducible micromixer has been developed in order to obtain fast mixing being subjected to the diffusion coefficient in such a way that not the mixing process but the reaction itself causes the changes in spectra that can be observed using time-resolved IR spectroscopy. This provides valuable information about the connection between structure and function in complex biochemical systems while keeping the sample consumption low, which is a driving force when investigating biological samples. In this sense, the use of synchrotron radiation as source of light for mid-IR detection greatly enhances the sensitivity of the method. The combination of the advantages of a high brilliance source that can be focused in small spots of up to 10 µm together with the versatility and small sample consumption of the micro-machined devices arises as a promising tool for the study of biochemical systems. On the other hand, we introduce infrared spectrometry as a novel molecule specific detection technique in separation systems. A CE microchip with mid-IR detection has also been designed and the mobility of different inorganic species as well as proteins on a CaF2 device has been for the first time demonstrated. The use of FT-IR as a detection method in CE on a chip allows to detect specific molecular features like the secondary structure of a protein and is therefore a suitable complementary method to standard detection methods.
The microchips were constructed by two highly IR transparent CaF2 windows separated by a photoresistant epoxy polymer layer in which different channels were developed according to the structures shown in the figures below. In the case of the mixer, 3 channels merge for mixing resulting in a final channel which is 15 µm broad and 10 µm deep. The meander structure allows following the sample for 5 cm. In the case of the CE chip, the separation channel is 10 µm deep, 100 µm broad and 4 cm long