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An oscillating feedback micromixer with no moving parts comprises an inlet channel, a diverging mixing chamber, a splitter, two feedback channels, and an outlet channel. Using the Coanda effect, two liquids are passively mixed in an oscillating feedback micromixer. Three oscillating feedback micromixers were experimentally investigated using two miscible liquids. The first had asymmetric feedback channels and a splitter, the second had symmetric feedback channels and a splitter, and the third had symmetric feedback channels and no splitter. Three chaotic mixing modes—vortex mixing, internal recirculation mixing, and oscillating mixing—were observed with increasing Reynolds numbers. The asymmetric oscillating feedback micromixer was determined to have the best mixing performance among the three micromixers. The splitter and asymmetric feedback channels can facilitate internal recirculation through feedback channels and fluidic oscillation, thereby enhancing the mixing efficiency. A completed mixing was achieved in the asymmetric micromixer. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1054–1063, 2015

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A countercurrent arrangement of immiscible liquid-liquid mini contactors based on droplets is described in this article. Mini mixers without any moving parts were used as the contactors. The single stage mini mixer consists of a top and bottom mixing chamber. Both of the mixing chambers have two recirculating channels on either side. In these mini mixers, a liquid was broken up into droplets that dispersed into other continuously flowing liquid, consequently achieving a mass transfer between the two liquids. To realize the countercurrent arrangement, the two liquids were alternately fed into the system from opposite ends by compressed air according to a periodic program. One period consists of the following stages: organic phase feeding stage, droplet aggregation stage I, aqueous phase feeding stage, and droplet aggregation stage II. This continuous countercurrent arrangement is without the defects of continuous countercurrent arrangements based on laminar flows and multiple-stage countercurrent arrangements based on droplets.