EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Microfluidic chips – which are used for the implementation of chemical, biochemical or biological processes in miniaturised devices – often contain complex channel networks having different geometries and sizes. Such structures can not be fabricated by conventional UV-photolithography using a single photomask. An appropriate method for creating the original structures (called master) is given by mask-less laser lithography (MALA), which allows writing of continuous-relief structures by application of the grey-scale mode with features down to the micrometer scale.

To the best of our knowledge, this study shows for the first time the implementation of MALA mastering of microfluidic structures with subsequent upscaling to a large area nickel working tool (630mm x 270mm) and replication by roll-to-roll UV-imprinting. The tool was made at Temicon GmbH via an electroforming process. Various smaller shims were made out of the master and welded together to a sleeve for the replication process by roll-to-roll imprinting. The design feature varied between channel cross-sections of 15µm x 15µm up to 300µm x 40µm. In addition, a process chain for chip manufacturing including inlet drilling by picosecond laser milling, UV assisted lamination of a sealing foil and screen-printing of detection electrodes is demonstrated.

The functionality of the chip prototypes was shown in the plant nutrient sensor MobiLab® of Pessl Instruments GmbH. This sensor system measures concentrations of inorganic ions in liquid samples. It is based on the principles of on-chip capillary electrophoresis (for separation of different ion species of a sample) and on-chip conductivity measurement (for quantification of the concentration of each individual ion species) in a microfluidic chip. The sensor performance was characterized by nutrient concentration measurements of algae culture media of an industrial photo bioreactor. The measurements confirm the multi-parameter measurement capabilities of the system by a characterization of NO3, Cl, SO4, K and Na concentrations.