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The fabrication of three-dimensional (3D) microfluidic networks entirely made of SU-8 with integrated electrodes is reported. The described technology allows the fabrication of uncrosslinked SU-8 dry film on a polyester (PET) sheet and its subsequent lamination to form closed microstructures. Unlike other reported methods, transferred layers are patterned following the bonding step allowing a more accurate and simple alignment between levels than techniques using already patterned layers. Dry release of the complete polymer microstructure was demonstrated. Flexible microfluidic chips were obtained. This technique uses simple tools and no wafer bonder is used but lamination techniques which are more collective processes. Limitations in the method for layers thicker than 50 µm have been observed and are discussed. Hydraulic flow experiments have been performed to study the deformation of the cover layer which could influence adjacent flow in a three-dimensional configuration. Important deformations have been observed for layers 10 µm thick and an average pressure greater than 100 kPa. No deformations have been noted for layers with thicknesses greater than 35 µm and for average pressures up to 200 kPa. No failures occurred within the range of the experimental set-up, i.e. up to 300 kPa.

An electrochemical microbiosensor involving NAD‐dependent dehydrogenase has been designed and developed using silicon technology. The sensor is based on a weakly polarized two‐gold microelectrode system without any reference electrode. The process allowed mass production of miniaturized devices. An enzymatic solution including diaphorase and NAD‐dependent dehydrogenase was confined in the microstructure by means of a semi‐permeable membrane. The biocompatibility of the various materials was verified and the gold electrodes were electrochemically characterized. The assay of D‐lactic acid was taken as an example using D‐lactate dehydrogenase. The sensitivity and detection limit of the microbiosensor were 8 μA mM–1cm–2and 0.01 mM respectively. Its lifetime was 3 weeks.