We have designed a bio/chemical microsystem for online monitoring of glucose concentrations during fermentation. The system contains several passive microfluidic components including an enzyme reactor, a flow lamination part and a detector. Detection is based on the reaction of hydrogen peroxide, that is produced from glucose in an enzyme reactor, with luminol. This chemiluminescent reaction generates light that is detected by an integrated back-side contacted photodiode array. Various tests during fabrication are outlined with the emphasis on microwave detected photo conductance decay. The presented microsystem has both fluidic and electrical connection points accessible from the backside. This allows simultaneous testing of both fluidic and electrical parts before dicing the wafer.
Buried optical channel waveguides integrated with a fluidic channel network on a planar microdevice are presented. The waveguides were fabricated using silica-on-silicon technology with the goal to replace bulk optical elements and facilitate various optical detection techniques for miniaturized total analysis systems or lab-on-a-chip systems. Waveguide structures with core layers doped with germanium were employed for fluorescence measurements, while waveguides with nitrogen- only doped core layers were used for absorbance measurements. By the elimination of germanium oxygen deficiency centers transmission of light down to 210nm was possible, allowing absorance measurements in the mid and far UV region (210 to 280nm), which is the region where a large number of different molecules absorb light. Robust, alignment-free microdevices, which can easily be hooked up to a number of light sources and detectors were used for fluorescence measurements of two dyes, fluorescein and Bodipy, and absorbance measurements of a stres-reducing drug, propranolol. The lowest detected concentrations were 250pM for fluorescein, 100nM for Bodipy and 12(mu) M for propranolol.
Microfabrication had a major impact on electronics and is expected to have an equally pronounced effect on chemistry and life sciences. Exploitation of these scientific fields is becoming increasingly dependent on the availability of systems that can perform fast accurate analyses, using minute volumes of sample. By combining microfluidics with micromechanics, microoptics, and microelectronics, systems can be realized that perform complete analyses. The possibility of realize structures with sizes that are in the same range as biological cells makes microtechnology especially interesting for cell analysis. Cell analysis already forms an important, integral part of medical diagnostics and research. Microtechnology provides the opportunity to refine existing cell analysis tools but also allows fabrication of instruments that cannot be realized with conventional technologies. Examples of first steps along this path are provided.
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