Andreas Gerlach

High-voltage contactless conductivity-detection for lab-on-chip devices using external electrodes on the holder

The detection of ionic species in a polymeric planar electrophoresis device by contactless conductivity measurement is described. To our knowledge this is the first report of such measurements carried out with external electrodes which are part of the holder rather than the separation chip itself. The approach allows the use of bare devices as used for optical measurements, which greatly simplifies the method. The use of a sine wave of 100 kHz of a high amplitude of 500 V for cell excitation assures high sensitivity which is demonstrated with electropherograms for alkali and heavy metal ions as well as inorganic anions and carboxylates at concentrations between 10 and 50 µM. The determination of underivatized amino acids was also possible by using a buffer in the alkaline region where these species are present in anionic form. Detection limits were found to be in the order of 1–5 µM for the inorganic ions and between about 5 and 50 µM for the organic species.

Large area polymer replication for microfluidic devices

A huge market development is expected for modern drug discovery and genomic analysis when rapid parallel analysis of a large number of samples gets available at affordable costs. The state of the art shows that low cost devices can be fabricated in mass production by micromolding of polymers. In close collaboration, Greiner Bio-One and Forschungszentrum Karlsruhe have developed a single-use plastic microfluidic capillary electrophoresis (CE) array in the standardized microplate footprint. This paper presents the results of experiences which show that hot embossing with a mechanically micromachined molding tool is the appropriate technology for low cost mass fabrication. A subsequent sealing of the microchannels allows sub-microliter sample volumes in 96- channel multiplexed microstructures.

LAB-ON-A-CHIP - SYSTEME FÜR DIE BIOMEDIZINISCHE FORSCHUNG UND DIAGNOSTIK

: In todays biomedical research and diagnosis, a number of substances and agents have to be checked. Frequently, plastic micro titer plates are used for this purpose as large-area test platforms. For the first time, plastic micro titer plates with 96 identical microfluidic labon-a-chip structures for simultaneous capillary electrophoresis (CE) have now been produced using microtechnical fabrication methods. Such structures are suited for e.g. the separation of biomolecules. In completely sealed microfluidic channel systems, smallest sample volumes can be processed, separated, mixed with other substances, or detected. Due to the small channel dimensions, these microfluidic systems are characterized by very small sample volumes needed.

Fabrication of Disposable Plastic Microplates with 96 Integrated Microfluidic Capillary Electrophoresis (CE) Structures for High Throughput Screening (HTS)

A novel microfluidic platform based on a standard microtiter plate has been developed by the Greiner Bio-One company and the Forschungszentrum Karlsruhe in Strategic cooperation. Instead of 96 wells, this novel platform accommodates 96 identical microfluidic CE structures on the same surface area (approx. 128 mm x 85 mm). The metal mold insert generated by micromilling possesses 96 inversely shaped CE structures that are molded into positive structures of PMMA or COC by vacuum hot embossing. In a further fabrication step, the obtained filigree microchannel structures are covered by an adapted, large-area cover plate to obtain real microcapillary structures. First tests demonstrated that these microcapillary structures have a good filling behavior. It may therefore be concluded that the channel geometry is accurate and homogeneous.