Integration of geometric separation mechanisms by implementing curved constrictions in a biochip microchannel fluidic separator

Abstract

This paper investigates the effectiveness of using curved constrictions in the bifurcation region of T-type fluid separators for promoting flow development in the intervals between bifurcations. A design of biofluid separator is proposed and a mathematical analysis and a numerical simulation of the blood flow in microchannels are conducted. The design is based on a modification of an existing T-shaped biochip device which consists of a main channel and a series of perpendicularly positioned side channels. By means of bifurcation effect, the blood is separated into plasma concentration flow from the side channels and blood cell concentration flow from the main channel. In this design, curved constrictions are inserted between bifurcations to replace the original straight channel section, so that the constriction and curved channel effects can be induced apart from the existing bifurcation effect. The mathematical analysis is aimed to the flow field and shear stress of the blood fluid in the microchannel geometries employed in the current design, including bifurcation, constriction and curved channel. The numerical simulation and mathematical analysis result in agreed conclusions, giving some insights into the importance of the relevant geometries in promoting biofluid separation. The main results can be summarised as follows: (i) the constrictions can largely increase the shear stress by the ratio of square of the reduction of the sections between the constriction and parent main channel. (ii) The curved channel intervals can induce centrifugal force, smoothly transit the flow field and increase the chances depleting fluid from the cell-free layer. (iii) The thickness of the boundary layer skimmed into the side channels from the main channel is decreased in this design and can be controlled, falling into the cell-free layer region by adjusting the geometry of the side channels.

Keywords:

• blood fluid separation
• microfluidic device
• microchannel device
• cross-flow filtration
• modelling and simulation

Acknowledgements

This is a following on study from the authors' work in processing the UK's EPSRC project ‘3D-MINTEGRATION’, referenced EP/C534212/1. The authors thank Prof Marc Desmulliez, Dr Mayur Patel and Dr Maiwenn Kersaudy-Kerhoas for co-authoring the previous papers (Xue et al. 2011a; 2011b; 2011c) which were funded by the above project. The authors would also like to acknowledge the contribution from Prof Desmulliez and Dr. Kersaudy-Kerhoas concerning the original separator (Kersaudy-Kerhoas et al. 2010) which is the prototype for the design modification in the current article.