Microfluidic Separation and Enrichment of Escherichia coli by Size Using Viscoelastic Flows

Here, we achieve the separation and enrichment of Escherichia coli clusters from its singlets in a viscoelastic microfluidic device. E. coli, an important prokaryotic model organism and a widely used microbial factory, can aggregate in clusters, leading to biofilm development that can be detrimental to human health and industrial processes. The ability to obtain high-purity populations of E. coli clusters is of significance for biological, biomedical, and industrial applications. In this study, polystyrene particles of two different sizes, 1 and 4.8 mu m, are used to mimic E. coli singlets and clusters, respectively. Experimental results show that particles migrate toward the channel center in a size-dependent manner, due to the combined effects of inertial and elastic forces; 4.8 and 1 mu m particles are found to have lateral equilibrium positions closer to the channel centerline and sidewalls, respectively. The size-dependent separation performance of the microdevice is demonstrated to be affected by three main factors: channel length, the ratio of sheath to sample flow rate, and poly(ethylene oxide) (PEO) concentration. Further, the separation of E. coli singlets and clusters is achieved at the outlets, and the separation efficiency is evaluated in terms of purity and enrichment factor.

Automated summary

Here, we demonstrate the separation and enrichment of Escherichia coli clusters from its singlets using a viscoelastic microfluidic device. The ability to obtain highly pure populations of E. coli clusters is crucial for various applications in biology, biomedicine, and industry. Experimental results show that particles of different sizes migrate towards the center of the channel due to the combined effects of inertial and elastic forces. The size-dependent separation efficiency is influenced by channel length, sheath-to-sample flow rate ratio, and poly(ethylene oxide) concentration.