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An efficient fluid mixing performance was achieved at the microand milliscale by a new design "Elis" in a wide range of Reynolds numbers. The micromixer is composed of internal walls and circular obstacles inducing three mass-transfer mechanisms: reduction of the diffusion path; change of the flow direction/vortex generation, and split and recombination of streams. The design was proposed and optimized by numerical simulations, allowing its application as micro-or millidevices. The device performance was numerically assessed by computational fluid dynamics (CFD) in the mixing process of two systems (vegetable oil/ethanol, and water/ethanol) for a Reynolds number range of 0.01−100 and also in the biodiesel synthesis for a residence time range of 10− 180 s. High mixing indexes (M = 0.985) were observed for the oil/ethanol system at low Reynolds numbers of 0.01 and 10. The CFD predictions for oil conversion were 91.32% (height of 1000 μm) and 92.22% (height of 2000 μm) for a residence time of 30 s. For the water/ethanol system, higher mixing indexes were 0.93 at Re = 1, increasing to a maximum of 0.99 at Re = 50 and 100. The numerical results demonstrated good performance of Elis as a millidevice, providing mixing efficiencies similar or even higher than microdevices from the literature.

An innovative method of alcoholic fermentation was proposed by developing a microfluidic device with millichannels filled with yeast immobilized in alginate hydrogel, manufactured by a new robotic system. We propose and build an automatic equipment consisting of a modified three‐dimensional (3D) printer with two independent systems, a module with a syringe for the injection of solutions/hydrogels and a conventional head with a fused filament fabrication mechanism. The methodology consisted of hydrogel 3D printing tests, the manufacture of millireactors with immobilized yeast and the application of the millireactors in alcoholic fermentation. The 22G needle provided the best printing accuracy in tests with hydrogel. The cells were homogeneously distributed by alginate and their concentration did not influence ethanol production. The optimal millireactor configuration was 2% alginate solution containing 25 g L−1 cells, achieved average ethanol production of 11.24 ± 0.015 g L−1, with productivity of 22.49 g L−1 h−1 and efficiency of 44%.

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