A small-scale study of nonlinear blood rheology shows rapid transient transitions

The mechanical properties of human blood are incompletely understood and constitute an underdeveloped area of study, prohibiting mechanically-based clinical diagnoses. Using the unique transient rheological signature of a blood sample, there is a possibility that blood rheology measurements could be used as a method of diagnosis and/or differentiation. We present here the response of blood to large amplitude oscillatory shear (LAOS) and reversing flow ramps, where hysteresis curves are typically formed. Results of these tests are visualized by blood "mechanical contours" that have the advantage of depicting the evolving mechanical properties of the material over a wide range of flow conditions. The sequence of physical process (SPP) method is applied to elucidate the changes undergone by the blood during the transient flows. This method is advantageous because it allows for the analysis of a wide range of transient flow protocols, rather than being restricted to strictly sinusoidal functions. We show a novel approach to the analysis of the large amplitude oscillatory shear tests in the form of mechanical contour maps. We also show the Cole-Cole plots and analysis for LAOS measurements using the same blood measurements. This allows a complete picture of the mechanical properties of the blood and a possible basis for comparison to pathological mechanical markers moving forward.