Mixing Enhancement By Gravity-dependent Convection in a Y-shaped Continuous-flow Microreactor

• Published in: Microgravity science and technology 2022-09, Vol.34 (5), Article 90
• Main Authors: Bratsun, Dmitry A., Siraev, Ramil R., Pismen, Len M., Mosheva, Elena A., Shmyrov, Andrey V., Mizev, Alexey I.
• Format: Article
• Language: English
• Subjects: Aerospace Technology and Astronautics; Chemical engineering; Chemical reactions; Classical and Continuum Physics; Continuous flow; Convection; Diffusion; Diffusion layers; Diffusion rate; Engineering; Fluid flow; Fluid mechanics; Free convection; Gravity; Mathematical models; Microbiology; Microfluidic devices; Microreactors; Numerical simulations; Original Article; Reagents; Solutes; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; The effect of gravity on non-equilibrium processes in fluids; Three dimensional models; Tubes
• ISSN: 1875-0494; 0938-0108; 1875-0494
• DOI: 10.1007/s12217-022-09994-9

Microfluidic devices are widely used in microbiology, fine organic synthesis, pharmaceuticals, biomedicine, etc. Most applications require rapid mixing of the fluids that pass through the microfluidic chip. Continuous-flow microreactors used in flow chemistry have a characteristic channel size that is small enough, compared to standard laboratory size in fluid mechanics but large enough to render the diffusion mixing mechanism ineffective. In this work, we study, experimentally and theoretically, the efficiency of using various mechanisms of natural convection for the mixing of fluids entering the microfluidic chip. Solutions typically differ in buoyancy and diffusion rates of solutes, making them sensitive to gravity-dependent instabilities such as Rayleigh-Taylor convection, double diffusion, and diffusion layer convection. We consider a Y-shaped microreactor, which is, on the one hand, the simple scheme of mixing and, on the other hand, a typical element of a microfluidic network. We assume that two miscible solutions independently enter through different tubes into a common channel, where they come into contact and begin to mix. For simplicity, we do not consider chemical reactions in this paper. For each type of instability, we numerically estimated the characteristic channel length, after which complete mixing of the solutions occurs. The numerical simulations are performed in the framework of the 3D model. Finally, we compare the experimental data and numerical results.