Rapid Microfluidic Mixing Method Based on Droplet Rotation Due to PDMS Deformation

Zichao Wang,Shanshan Li,Chunyang Wei,Junwei Li,Feng Pan,Tiejun Li,Chengzhuang Yu

doi:10.3390/mi12080901

Abstract

Droplet-based micromixers have shown great prospects in chemical synthesis, pharmacology, biologics, and diagnostics. When compared with the active method, passive micromixer is widely used because it relies on the droplet movement in the microchannel without extra energy, which is more concise and easier to operate. Here we present a droplet rotation-based microfluidic mixer that allows rapid mixing within individual droplets efficiently. PDMS deformation is used to construct subsidence on the roof of the microchannel, which can deviate the trajectory of droplets. Thus, the droplet shows a rotation behavior due to the non-uniform distribution of the flow field, which can introduce turbulence and induce cross-flow enhancing 3D mixing inside the droplet, achieving rapid and homogenous fluid mixing. In order to evaluate the performance of the droplet rotation-based microfluidic mixer, droplets with highly viscous fluid (60% w/w PEGDA solution) were generated, half of which was seeded with fluorescent dye for imaging. Mixing efficiency was quantified using the mixing index (MI), which shows as high as 92% mixing index was achieved within 12 mm traveling. Here in this work, it has been demonstrated that the microfluidic mixing method based on the droplet rotation has shown the advantages of low-cost, easy to operate, and high mixing efficiency. It is expected to find wide applications in the field of pharmaceutics, chemical synthesis, and biologics.

Highlights

Microfluidics has attracted much attention in chemical analysis, pharmacology, biologic, and catalysis due to its easy integration, multi-function, and miniaturization [1,2,3,4].Among the many applications, microfluidic mixing is crucial due to the need for homogenization of multiple reagents in biological or chemical reactions [5,6,7]
A well-known problem in microfluidic mixing is its efficiency due to its feature by laminar flow; the mixing is dominated by molecular diffusion, which is time-consuming with low efficiency
Fluorescence Images of Mixing Caused by Droplet Rotation

Summary

Introduction

Microfluidic mixing is crucial due to the need for homogenization of multiple reagents in biological or chemical reactions [5,6,7]. A well-known problem in microfluidic mixing is its efficiency due to its feature by laminar flow; the mixing is dominated by molecular diffusion, which is time-consuming with low efficiency. For this reason, many methods have been studied to enhance the mixing to achieve rapid, homogenous mixture in lab-on-a-chip (LOC) systems [8,9,10].

Methods

Results

Conclusion