Blood flows on passive microfluidics – Role of blood physiology and biomechanical properties

Abstract

The study of blood flow and rheology is essential for understanding fundamental flow physics and blood behaviour in physiological/pathological conditions. Passive microfluidic flow has emerged as a promising platform for developing blood diagnostic tools for assisting in health monitoring. This work, describes recent work on passive blood flows in microfluidic devices, where the influence of blood physiology and blood biomechanical properties was studied. Hemorheological factors of human blood and erythrocyte suspensions where quantified, and the flow of samples in hydrophilic/superhydrophilic rectangular microchannels was characterised using micro-Particle Image Velocimetry and Particle-Tracking techniques. The effects of altered physiological factors, such as erythrocyte concentration (haematocrit), deformability and aggregation were investigated, and meniscus velocities, velocity profiles, local and bulk shear rates were derived and correlated. The findings suggested that viscosity and erythrocyte deformability and concentration affect negatively the velocity of blood in the channel. Interestingly, increased erythrocyte aggregation was observed to have a non-monotonic effect on the velocity of the fluids tested, favouring samples of normal deformability and reduced haematocrit. The relatively high shearing rates observed near the entrance of the channels seem to substantially minimise erythrocyte aggregation, therefore supressing the non-Newtonian nature of the samples for a substantial part of the channel length.