Numerical investigation of mixing efficiency in Janus micro-mixer using lattice Boltzmann method

Abstract

Droplet micro-mixing is a critical aspect limiting the accuracy of chemical analysis and the quality of drug screening, requiring efficient mixing of target concentrations in a limited volume. In this paper, the ternary dilute solute lattice Boltzmann model is used to study the mixing processes and mechanisms of solutes inside Janus droplets. The influence of three factors including droplet velocity, tilt angle and volume ratio on mixing efficiency is examined. The results show that there is a main circulation and a “dead zone” inside the droplet. With increasing droplet velocity, both the intensity and the occupied volume of the main circulation increase, which make the mixing efficiency increase. At different tilt angles, the difference in the strength of the internal flow field makes the mixing efficiency of the “windward part” greater than that of the “leeward part.” When keeping the volume of the r-phase constant and increasing the volume of the g-phase, the diffusion distance of solute is shortened and the occupied volume of the main circulation is reduced. The diffusion distance competes with the reinforcing effect of the flow field, which finally shows a tendency that the larger the r: g, the faster the mix is complete. The results will provide theoretical support for further improvement of the droplet micro-mixer efficiency.