Efficient microfluidic enrichment of nano‐/submicroparticle in viscoelastic fluid

Abstract

The enrichment and focusing of the nano‐/submicroparticle (e.g., 150–1000 nm microvesicle shed from the plasma membrane) in the viscoelastic fluid has great potentials in the biomedical and clinical applications such as the disease diagnosis and the prognostic test for liquid biopsy. However, due to the small size and the resulting weak hydrodynamic force, the efficient manipulation of the nano‐/submicroparticle by the passive viscoelastic microfluidic technology remains a major challenge. For instance, a typically long channel length is often required to achieve the focusing or the separation of the nano‐/submicroparticle, which makes it difficult to be integrated in small chip area. In this work, a microchannel with gradually contracted cross‐section and high aspect ratio (the ratio of the height to the average width of channel) is utilized to enhance the hydrodynamic force and change the force direction, eventually leading to the efficient enrichment of nano‐/submicroparticles (500 and 860 nm) in a short channel length (2 cm). The influence of the flow rate, the particle size, the solid concentration, and the channel geometry on the enrichment of the nano‐/submicroparticles are investigated. With simple structure, small footprint, easy operation, and good performance, the present device would be a promising platform for various lab‐chip microvesicle‐related biomedical research and disease diagnosis.

Electrophoresis of a highly charged fluid droplet in dilute electrolyte solutions: Analytical Hückel‐type solution

“…Liquid droplet is a very versatile colloidal entity involved in many practical applications, such as in drug delivery in the form of the liposome [1,2] or the liquid metal droplet [3][4][5], in food or cosmetic industries as microemulsions and nanoemulsions [6,7], in microfluidic and nanofluidic operations as the purification platform of proteins and other substances [8][9][10], and in the pharmaceutical Abbreviation: NACE, nonaqueous capillary electrophoresis. industry as the microreactor of therapeutics production [11] The tiny size of a liquid droplet provides nearly perfect mixing performance as well as high mass transfer and heat transfer rates, properties akin to essentially all of the operations in chemical engineering and its related industries [12].…”

Elastic‐inertial separation of microparticle in a gradually contracted microchannel

“…In the viscoelastic fluid, the microparticle was dominantly subjected to the elastic lift force (F e ) and the inertial lift force (F i ) [28,29,[32][33][34][35]. The elastic lift force is mainly induced by the nonuniform normal stress differences, which can be divided into F e→w that points to the wall and F e→c that points to the channel center [28].…”

“…The gradually contracted microchannel and the dominant forces on particle are shown in Figure 1. The gradually contracted structure would generate single low shear rate region at the channel center and enhance the driving forces [32,33]. When the microchannel is filled with the fluid, the elasticity of which is comparable with the inertia, such as the 0.3-wt% poly(vinylpyrrolidone) (PVP) solution, large and small particles would be subjected to F e in the different directions.…”

“…It indicates that F e→w had played an important role in the lateral migration of the 10-µm particle, and it promoted the 10-µm particle to fast move to the equilibrium positions At the flow rate of 62.5 µl/min (Re = 20.24 and Wi = 5.81), the 4-µm particles were distributed from r′ = ∼-0.23 to r′ = ∼0.23, and the bandwidth was smaller than that at the flow rate from 10 to 50 µl/min. It is because a stronger F e pointing to the channel center was induced by the gradually contracted structure at a higher flow rate [32,33], and F i on the 4-µm particle was weak because of the small particle size. Eventually, the 4-µm particle was focused in a small bandwidth at the channel center.…”

“…The efficient separation was achieved at the high flow rate of 62.5 µl/min, and the separation efficiency and the separation purity of the 10-µm particle were 99% and 97.2%, respectively (shown in Table S1). In the gradually contracted microchannel, the migration principle of the particle in the 0.3-wt% PVP solution was quite different from that in the 8-wt% PVP solution [32,33]. For instance, different sized particles in the 8-wt% PVP solution were focused at the center of the gradually contracted microchannel [32,33].…”