Effects of biomechanical properties of blood on surface tension-driven flows in superhydrophilic channels

Abstract

Surface tension driven microfluidic flows offer low-cost solutions for blood diagnostics due to the pump-less flow handling. Κnowledge of the influence of the biomechanical properties of blood on such flows is key to design such devices, however a systematic examination of that influence is lacking in the literature. We report on the effects of specific haemorheological factors for flows in a superhydrophilic microchannel. Whole human blood and erythrocyte suspensions in phosphate buffer and Dextran solutions were tested. Heat-treated counterparts of the aforementioned samples were produced to alter the deformability of the cells. The flow of the samples was imaged and characterised using micro-Particle Image Velocimetry and tracking techniques to probe the effects of haematocrit, erythrocyte aggregation and deformability. Meniscus velocities, velocity profiles in the channel, and local and bulk shear rates were derived. The mean velocity of blood was affected by the increasing sample viscosity and the reduced erythrocyte deformability as expected. The increased erythrocyte aggregation appeared to affect more the shape of the velocity profiles in the normal, compared to the heat-treated samples. Very high shear rates are observed in the early stages of the flow, suggesting high erythrocyte disaggregation, persisting sufficiently strong until the flow reaches the end of the channel.

Red blood cell sedimentation rate measurements in a high aspect ratio microchannel

“…The geometry of the testing channel was chosen in order to favour the surface tension driven (STD) flow, as described in detail by Pasias et al 2022 [ 25 ]. A high aspect ratio channel (>20 : 1) was adopted, with a converging geometry of 3 degrees inclination for the first part of the channel, followed by a straight section of 2 mm (±0.1 mm) width, which is the imaging area; the effective length of the channel was 35 mm ( Fig.…”