Particle-Liquid Transport in Curved Microchannels: Effect of Particle Volume Fraction and Size in Dean Flow

Microfluidic transport in spiral channels is a promising flow-driven mechanism for applications such as cell sorting and particle focusing. Spiral channels have unique curvature-driven flow characteristics that trigger Dean flow, forcing the liquid to be displaced towards the outer wall of the microchannel due to centrifugal force. Despite the growing popularity of these applications, there is a lack of physical understanding of such particle-fluid two-phase transport in a spiral microchannel. To address this gap, in this paper we employ a coupled particle-transport-microfluidic-flow (two-phase) computational fluid dynamics model for probing such two-phase transport in a curved microchannel that gives rise to Dean flow. Our simulations reveal that the presence of the particles has two effects: (1) they reduce the Dean flow effect of skewing the flow field towards the outer wall, i.e., the flow becomes more symmetric (or the velocity maximum moves towards the center of the channel) and (2) there is a significant alteration in the vortex patterns associated with the Dean flow. We quantify the drag and lift forces experienced by the particles and propose that the corresponding particle-imparted drag and the lift forces on the continuous phase counter the effect of the curvature-driven centrifugal force on the continuous phase, thereby altering the Dean flow characteristics. Furthermore, we anticipate that such precise quantification of the forces experienced by these particles, present in finitely large concentration in microfluidic Dean flow, will be critical in designing Dean flow effect driven size-based microfluidic particle separation.