Inertial Focusing of Microparticles in Curvilinear Microchannels

Abstract

A passive, continuous and size-dependent focusing technique enabled by “inertial microfluidics”, which takes advantage of hydrodynamic forces, is implemented in this study to focus microparticles. The objective is to analyse the decoupling effects of inertial forces and Dean drag forces on microparticles of different sizes in curvilinear microchannels with inner radius of 800 μm and curvature angle of 280°, which have not been considered in the literature related to inertial microfluidics. This fundamental approach gives insight into the underlying physics of particle dynamics and offers continuous, high-throughput, label-free and parallelizable size-based particle separation. Our design allows the same footprint to be occupied as straight channels, which makes parallelization possible with optical detection integration. This feature is also useful for ultrahigh-throughput applications such as flow cytometers with the advantages of reduced cost and size. The focusing behaviour of 20, 15 and 10 μm fluorescent polystyrene microparticles was examined for different channel Reynolds numbers. Lateral and vertical particle migrations and the equilibrium positions of these particles were investigated in detail, which may lead to the design of novel microfluidic devices with high efficiency and high throughput for particle separation, rapid detection and diagnosis of circulating tumour cells with reduced cost.

Microparticle Inertial Focusing in an Asymmetric Curved Microchannel

“…Therefore, it is a challenging task to accurately anticipate the steady state condition of the Dean vortices. It has been demonstrated in our previous work, that in a symmetric curvilinear microchannel with a uniform width of 350 µm and a curvature angle of 280 • , when the fluid flow approaches the transition region, a shift in the velocity maxima is observed near the centerline of the channel [63]. Thereafter, the outer wall becomes the inner wall and the velocity maxima occurs closer to the inner wall, rather than to the centerline.…”

“…According to Figure 4c, the stream of medium particles is seen near the centerline while most of the small particles travel between the centerline and W2. Inertial focusing in a symmetric microchannel with the same curvature angle of 280 • was previously studied in our group [63]. The focusing behavior of microparticles of the same diameters in an asymmetric microchannel is also compared to that in our previous study.…”

“…Additionally, in the microfluidics studies involving particle or cell separation in a spiral geometry, this pattern is preserved up to a specific Dean number [47]. According to some numerical studies, the main flow velocity has a maximum somewhere between the centerline and the inner wall [63,74]. F L is always directed from the velocity maxima towards the channel walls, regardless of the particle vertical position.…”

“…Moreover, for each binary combination of the particles, the optimum Reynolds number, defined as the one at which the largest distance between the focal bands of two particles at the transition region occurs, was reported. Lastly, the focusing behavior of the particles in the current asymmetric microchannel was compared to the symmetric design with the same curvature angle, which was previously done in our group [63]. An asymmetric microchannel configuration with such a high curvature angle and the comparison of its performance with the corresponding symmetric design over a wide range of Reynolds number, constitutes the significance of this study.…”

Síntese Em Sistemas Microfluídicos De Nanopartículas De Cdte E De Ag Para Estudo Qualitativo De Interação Em Fluxo E Preparação De Filmes Finos Desses Nanomateriais

“…Na equação de Reynolds, ⍴ é a densidade do fluido, é a velocidade de escoamento, ℎ é diâmetro hidráulico da tubulação e é a viscosidade do fluído (SQUIRES e QUAKE, 2005;ÖZBEY et al, 2016;SUN et al, 2016 (DITTRICH, 2005;WHITESIDES, 2006;COLTRO et al, 2007). Um dos grandes desafios da microfabricação é conseguir projetar um reator microfluídico com geometria adequada para otimizar a eficiência de mistura e a transferência de massa e calor com base nas características de uma reação especifica.…”