Hiroshi Ohue

Demonstration of the Enhanced Mixing and Reaction Ability of an Alternate Pumping Microreactor With Visualization of the Mixing Field and the Reaction Field

In order to enhance the mixing and reaction capabilities of micromixers and microreactors, we had proposed a novel system termed alternate pumping microreactor (APMR) and had demonstrated that the APMR could generate a thin-layered structure under a particular pumping condition. This flow pattern should enhance the abovementioned capabilities. In this paper, we visualized the dilution process of methylene blue solution with water in the APMR and established a method to obtained the concentration field from the captured image according to the relation between the methylene blue concentration and the saturation of the captured color. To assess the reaction field, visualization of the reaction of ferrous sulphate and potassium thiocyanate was adopted. These visualization results suggested that the APMR enhanced the mixing and reacting capabilities and the time and channel length required for the reaction to complete were two order orders of magnitude lesser than those in the case of the ordinary reactor.Copyright

Estimation of mixing fields in micromixers and microreactors by visualization method using methylene blue solution

During the development of micromixers and microreactors, it is important to assess the concentration field and mixing status in their microchannels. Therefore, this study establishes a visualization method for evaluating the concentration field using images of dilution of a methylene blue solution with water. Noted that the original methylene blue solution is deep blue before it is mixed with water; it becomes paler once it is diluted, as observed against a white background. Because the methylene blue concentration has a highly reliable relationship with the saturation of the captured color, the local methylene blue concentration can be determined on the basis of a calibration result obtained in advance. The saturation value is affected not only by the concentration but also by the optical effect of the channel walls. Therefore, we established a method of eliminating the channel wall effect. As a trial, we estimated the concentration field in our novel microreactor using the proposed visualization method and estimated the mixing status in the microchannel. We showed that the proposed visualization method effectively estimated the concentration field and mixing status in micromixers and microreactors.Graphical Abstract