Abstract
Inertial microfluidics has been used in recent years to separate particles by size, with most efforts focusing on spiral channels with rectangular cross sections. Typically, particles of different sizes have been separated by ensuring that they occupy different equilibrium positions near the inner wall. Trapezoidal cross sections have been shown to improve separation efficiency by entraining one size of particles in Dean vortices near the outer wall and inertially focusing larger particles near the inner wall. Recently, this principle was applied to a helical channel to develop a small-footprint microfluidic device for size-based particle separation and sorting. Despite the promise of these helical devices, the effects of channel geometry and other process parameters on separation efficiency remain unexplored. In this paper, a simplified numerical model was used to estimate the effect of various geometric parameters such as channel pitch, diameter, taper angle, depth, and width on the propensity for particle separation. This study can be used to aid in the design of microfluidic devices for optimal size-based inertial particle separation.
Highlights
Size-based particle separation plays a key role in many biomedical and environmental applications1 such as the separation of tumor cells2,3 and leukocytes4 from blood samples, detection of pathogenic bacteria,5 and cell synchronization.6 Several microfluidics-based approaches have been developed for this purpose including dielectrophoretic,7 magnetophoretic,8 and acoustophoretic9 separation
The present paper presents a parametric study of the effect of particle diameter, channel pitch, channel diameter, taper angle, and channel depth and width on the focusing state of the particles in a helical channel using a simplified numerical model that relies solely on local flow parameters
The present paper examined the effects of various geometric parameters on size-based inertial particle separation in a helical channel using a calibrated numerical model, which shows good agreement with the experimental data in channels with various Re and aspect ratio (AR)
Summary
Size-based particle separation plays a key role in many biomedical and environmental applications such as the separation of tumor cells and leukocytes from blood samples, detection of pathogenic bacteria, and cell synchronization. Several microfluidics-based approaches have been developed for this purpose including dielectrophoretic, magnetophoretic, and acoustophoretic separation. Inertial microfluidic methods have been developed for size-based separation. Particles flowing through a straight rectangular microchannel will migrate to distinct equilibrium positions based on their size. These equilibrium positions are determined by balancing a shear-gradient lift force, which moves particles toward the walls, and a wall-induced lift force, which shifts particles away from the walls.. The wall-induced lift force results from an increase in pressure between the particle and the channel wall as it approaches the wall In these channels, up to four equilibrium positions may exist for each particle size, one on each wall, presenting challenges for the extraction of particles into separate outlets
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