Impact of viscosity ratio on the mixing efficiency of a core–shell structured droplet micromixer

• Published in: Microfluidics and nanofluidics 2022-11, Vol.26 (11), Article 89
• Main Authors: Ge, Han, Chen, Jiawang, Ren, Ziqiang, Zhu, Ronghua, Limanowski, Ruby
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Biomedical Engineering and Bioengineering; Convection; Core-shell structure; Deceleration; Droplets; Engineering; Engineering Fluid Dynamics; Flow distribution; Flow pattern; Internal flow; Microreactors; Mixing; Nanotechnology and Microengineering; Reagents; Research Paper; Viscosity; Viscosity ratio
• ISSN: 1613-4982; 1613-4990
• DOI: 10.1007/s10404-022-02595-3

A complete knowledge of the effect of viscosity on the mixing within a compound structured droplet is essential for the application using a droplet as the micro-mixer or micro-reactor. Most of the time, the reagents that need to be mixed possess different viscosities, making the viscosity of the droplet unevenly distributed before they are well mixed. Yet, the effect of the viscosity difference on the mixing process is still not entirely understood. In this work, the effect of viscosity on the internal mixing of a core–shell structured droplet is investigated numerically. The results show that the internal flow pattern of the droplet is determined by the droplet-to-continuous viscosity ratio. Mixing is increased with the decrease of the droplet-to-continuous viscosity ratio, but the increase decelerates when the viscosity ratio is smaller than 0.10. The change of the shell-to-core viscosity ratio will not affect the internal flow pattern, whereas, it will affect the convection, and thus the mixing. The highest or lowest viscosity is preferred to be set as the shell to achieve a quicker mixing.