Elastic‐inertial separation of microparticle in a gradually contracted microchannel

Abstract

Separation of microparticle in viscoelastic fluid is highly required in the field of biology and clinical medicine. For instance, the separation of the target cell from blood is an important prerequisite step for the drug screening and design. The microfluidic device is an efficient way to achieve the separation of the microparticle in the viscoelastic fluid. However, the existing microfluidic methods often have some limitations, including the requirement of the long channel length, the labeling process, and the low throughput. In this work, based on the elasticinertial effect in the viscoelastic fluid, a new separation method is proposed where a gradually contracted microchannel is designed to efficiently adjust the forces exerted on the particle, eventually achieving the high-efficiency separation of different sized particles in a short channel length and at a high throughput. In addition, the separation of WBCs and RBCs is also validated in the present device. The effect of the flow rate, the fluid property, and the channel geometry on the particle separation is systematically investigated by the experiment. With the advantage of small footprint, simple structure, high throughput, and high efficiency, the present microfluidic device could be utilized in the biological and clinical fields, such as the cell analysis and disease diagnosis.

Continuous sheathless particle separation in viscoelastic fluids with different rheological properties

“…The fluid flows through the gap between the large particle (β > 0.25) and the side wall, which increases the shear rate around the large particle. The compressive normal stress at near-center side of the large particle is increased, and a net elastic force in the direction towards the side wall is exerted on the large particle (Nam et al 2019a(Nam et al , 2020Tian et al 2022). Meanwhile, the net inertial lift force on the large particle is also in the direction towards the side wall (Lu et al 2017;Yuan et al 2018;Park et al 2019).…”

“…The existing passive methods of microparticle separation in the viscoelastic fluid can be divided into the sheath flow-based (Nam et al 2012;Lu and Xuan 2015b;Tian et al 2017;Fan et al 2020a) and sheathless (Li et al 2016Yuan et al 2017Yuan et al , 2019Yang et al 2011Yang et al , 2012Lee et al 2013;Nam et al 2015aNam et al , b, 2016Nam et al , 2019aNam et al , b, 2020Lu et al 2021;Tian et al 2022;Tan et al 2017;Fan et al 2020bFan et al , 2021 method. A co-flow microfluidic system is often adopted in the sheath flow-based method to produce a fluid interface between two flows, which allows for a size-selective movement of microparticle across the interface (Fei et al 2019).…”

“…From the perspective of particle separation strategy, the sheathless separation method can be divided into two categories: direct separation (corresponding to one-stage channel) and separation after focusing (corresponding to two-stage channel). The direct separation method has been utilized for the particle separation in the elastic-dominated flow (Li et al 2016Yuan et al 2019;Yang et al 2012;Lee et al 2013) and in the flow where the elasticity and the inertia are comparable (Nam et al 2019a(Nam et al , 2020Lu et al 2021;Tian et al 2022). For example, Li et al (2016) presented a rectangular microchannel with a high aspect ratio for the particle separation in the PEO solution (El=9.3-52.1) at the optimal flow rate less than 5 μL/min, where the elastic lift force was divided into two components with one drove the particle to the channel center and the other one pushed them toward the side wall.…”

“…A typically low flow rate was often adopted by the direct separation method in the elastic-dominated flow to generate a low flow resistance due to the high viscosity of the liquid (Li et al 2016Yuan et al 2019;Yang et al 2012;Lee et al 2013). Higher flow rate can be achieved in the viscoelastic flow where the elasticity and the inertia are comparable (Nam et al 2019a(Nam et al , 2020Lu et al 2021;Tian et al 2022. Nam et al (2019a successfully sorted small fungal cells and leukocytes in the 0.1% HA solution (El=0.28) at a flow rate of 100 μL/min.…”

“…Lu et al (2021) designed a repeating curve channel to control the inertial lift, the elastic force and the Dean drag on particles, and separated different sized partilces in the 200 ppm PEO solution at 102 μL/min. In our prior work, a gradually contracted microchannels was proposed and fabricated to separate microparticles in the 0.3 wt% PVP solution (El=0.2) at a flow rate of 62.5 μL/min (Tian et al 2022). In comparison to the direct separation method, the separation after focusing method (two-stage channel) only works for the particle separation in the viscoelastic fluid with high elasticity (Yuan et al 2017;Yang et al 2011;Nam et al 2015aNam et al , b, 2016Nam et al , 2019bTan et al 2017;Fan et al 2020bFan et al , 2021.…”