Rheological Characterization of Blood-Mimicking Fluids for Use in Particle Image Velocimetry

Blood-mimicking fluids (BMFs) are often used to investigate blood flow using physical replicas of vessels with cardiovascular disease. Particle image velocimetry (PIV) is used with silicone poly-dimethyl siloxane (PDMS) vascular models to visualize this flow. The challenge is creating a blood-mimicking fluid that matches the viscosity profile, viscoelasticity, and density of whole blood while also matching the refractive index (RI) of PDMS. Water-glycerol solutions are commonly used with sodium iodide (NaI) added to increase the RI without changing viscosity. However, NaI is expensive, stains easily, and turns fluids from optically clear to yellow in less than a day. Furthermore, without adding a shear-thinning agent such as xanthan gum, BMFs do not mimic the aggregation of red blood cells at low arterial shear rates. This study characterized 12 published BMF formulations with varying concentrations of water, glycerol, xanthan gum and NaI/urea. Rheological measurements were obtained using the Anton Paar MCR 302, RI was measured using an Abbe Refractometer, and density was found using a 10 ml pipette and analytical balance. It was found that solutions with 0.04 wt.% xanthan gum and a low ratio of glycerol to water best match the shear-thinning profile and viscoelasticity of whole blood over a wide range of shear rates. As well, urea is a cheaper alternative to NaI, as it can match the density, RI of PDMS, and viscosity of blood while maintaining a transparent colour. Overall, it was concluded that a blood-mimicking fluid with 51.9 wt.% water, 22.2 wt.% glycerol, 25.9 wt.% urea/NaI, and 0.04 wt.% xanthan gum was the best candidate for investigating blood flow with PIV