Adaptive Micromixer Based on the Solutocapillary Marangoni Effect in a Continuous-Flow Microreactor

Abstract

Continuous-flow microreactors are an important development in chemical engineering technology, since pharmaceutical production needs flexibility in reconfiguring the synthesis system rather than large volumes of product yield. Microreactors of this type have a special vessel, in which the convective vortices are organized to mix the reagents to increase the product output. We propose a new type of micromixer based on the intensive relaxation oscillations induced by a fundamental effect discovered recently. The mechanism of these oscillations was found to be a coupling of the solutal Marangoni effect, buoyancy and diffusion. The phenomenon can be observed in the vicinity of an air–liquid (or liquid–liquid) interface with inhomogeneous concentration of a surface-active solute. Important features of the oscillations are demonstrated experimentally and numerically. The periodicity of the oscillations is a result of the repeated regeneration of the Marangoni driving force. This feature is used in our design of a micromixer with a single air bubble inside the reaction zone. We show that the micromixer does not consume external energy and adapts to the medium state due to feedback. It switches on automatically each time when a concentration inhomogeneity in the reaction zone occurs, and stops mixing when the solution becomes sufficiently uniform.

Phase transitions on partially contaminated surface under the influence of thermocapillary flow

“…2012), various biophysical lab-on-chip diagnostic systems (Ju & Warrick 2013; Sinz, Hanyak & Darhuber 2013; Yamada & Ono 2015) and continuous-flow microreactors (Nieves-Remacha, Kulkarni & Jensen 2012; Bratsun et al. 2018). The characteristic size of these devices, which is usually of the order of one millimetre or less, defines spatial scales for mass transfer processes.…”

“…The last decade has been marked by a rapidly increasing interest in techniques for manipulation of single phase inclusions (droplets, bubbles or particles) in a liquid phase. These techniques are promising, first of all, from the viewpoint of numerous chemical and biophysical applications among which the most important are microfluidic devices for the production of emulsions (Song, Tice & Ismagilov 2003;Seemann et al 2012), various biophysical lab-on-chip diagnostic systems (Ju & Warrick 2013;Sinz, Hanyak & Darhuber 2013;Yamada & Ono 2015) and continuous-flow microreactors (Nieves-Remacha, Kulkarni & Jensen 2012;Bratsun et al 2018). The characteristic size of these devices, which is usually of the order of one millimetre or less, defines spatial scales for mass transfer processes.…”

Extended classification of the buoyancy-driven flows induced by a neutralization reaction in miscible fluids. Part 1. Experimental study

“…2003), combustion processes (Zeldovich & Kompaneets 1960), separation of uranium ore (Thomson, Batey & Watson 1984), chemical reactor design and technology (Levich, Brodskii & Pismen 1967; Jakobsen 2008), external control of continuous-flow microreactors (Jensen 2001; Bratsun et al. 2018; Bratsun & Siraev 2020), chemisorption (Lambert 1997; Karlov et al. 2007), etc.…”

“…Although the chemo-hydrodynamic pattern formation in a system of two reacting fluids was experimentally observed as early as 1888 (Quincke 1888), these studies were mainly descriptive by nature due to the complexity of these processes. However, a really consistent detailed study of the reaction-diffusion processes coupled with hydrodynamic phenomena started only a century later, since it was stimulated by many important technological applications including oil refining (Dupeyrat & Nakache 1978), photochemical polymerization (Evans & Uri 1949;Belk et al 2003), combustion processes (Zeldovich & Kompaneets 1960), separation of uranium ore (Thomson, Batey & Watson 1984), chemical reactor design and technology (Levich, Brodskii & Pismen 1967;Jakobsen 2008), external control of continuous-flow microreactors (Jensen 2001;Bratsun et al 2018;Bratsun & Siraev 2020), chemisorption (Lambert 1997;Karlov et al 2007), etc. Starting with the monograph (Levich 1962), the interaction between reaction-diffusion phenomena and hydrodynamic instabilities has attracted increasing interest because chemically induced changes of fluid properties, such as concentration, density, viscosity and surface tension, may result in the instabilities, which exhibit a large variety of convective patterns.…”

Switching Modes of Mixing Due to an Adjustable Gap in a Continuous-Flow Microreactor

“…At present, there are several examples of well-developed technologies based on the CFMR/AFMR for the production of pharmaceutical substances by the method of continuous-flow synthesis [9][10][11]13]. In the last few years, different types of convective micromixers for the AFMR unit have been proposed [13][14][15]. Furthermore, various techniques have been developed for mixing typically laminar flows in the CFMR.…”