A CFD Study to Improve the Cell Separating Efficiency of an Inertial Spiral Microfluidic Channel with Expansion Chambers

Abstract Separating circulating tumour cells (CTC) from other cells are important because they function as biomarkers to assess cancer stage and provide targeted treatment for cancer patients. Existing separation methods are time consuming and provide low efficacy and throughput. Spiral microfluidic devices aid to counter this with its high throughput and continuous separation. In this paper, cell separating efficiency is the main key measure to assess the performance of the microfluidic channel geometries. Expansion chambers are implemented to a conventional spiral microfluidic channel with different geometry to improve the cell separating efficiency through computational fluid dynamics (CFD) study using COMSOL Multiphysics 6.1 with the Laminar Flow and Particle Tracing physics model where the spiral microfluidic channel models are modelled using SolidWorks. Mesh independence study was conducted where the average element quality of tetrahedral mesh exceeds 0.7, indicating that the 1 mm element size is effective for discretizing the computational domain. The implementation of expansion chambers significantly improved the cell separating efficiency to 100% where all CTCs are separated into the targeted outlet and reduced cell separation process time by 37.78% to 0.448 seconds. This is possible with the bow tie geometry which has 2 sharp tips from the 45° undercut features that increases the velocity and vorticity of the fluid in that region.