NON-NEWTONIAN MICROFLUIDICS FOR BIOLOGICAL PARTICLE SEPARATION AND MANIPULATION

Abstract

Cell separation is an important clinical pre-processing step. Conventionally, blood is fractionated by density-dependent centrifugation, which, apart from requiring large bench top centrifuges, also imposes harsh conditions on cells which may compromise their viability and function. Microfluidics has been identified as a strong alternative due to the low shear stresses imposed on cells at the low Reynolds number flows, small sample volumes, and ease of integration of multiple modalities. Of late, there has been increasing interest in the field of non-Newtonian viscoelastic particle separation. Particles suspended in solutions of high molecular weight long-chain polymers experience a nonlinear radially-directed force arising from gradients in the first normal stress difference. In this thesis, a novel two-stage microfluidic device was developed for viscoelasticity-driven cell separation. The effectiveness of the device was demonstrated through the separation of cancer cells, P. Falciparum parasites and leukocytes from diluted whole blood with high efficiency and purity.