Visualizing and exploring nonlinear behavior, timescales, and mechanical signatures of human blood.

Human blood is an excellent example of a thixo-elasto-visco-plastic (TEVP), shear-thinning fluid, with an apparent yield stress. We demonstrate a series of unique strain-controlled experiments to elucidate the evolving elastic and viscous properties of human blood and show the associated unique viscoelastic and thixotropic signatures. The experimental techniques and procedures outlined here, and the robust mechanical analysis framework offers a window into the complex nonlinearity of the relationship between the microstructure and mechanical properties of human blood. Rather than using the traditional discrete Fourier transform to analyze the data, two contemporary methods, the MITlaos, Chebychev analysis technique, and the other sequence of physical processes (SPP), are applied to these oscillatory tests. These methods are advantageous because they both allow for the analysis of large amplitude oscillatory shear flow. These frameworks will highlight how the blood undergoes thickening-thinning and hardening-softening cycles that are directly related to microstructures during large amplitude oscillatory shear flow. We show these results with a series of Cole-Cole and Lissajous-Bowditch plots, then compare to an aqueous solution of xanthan gum and glycerol. The analysis presented here is independent of a specific TEVP rheological model. (We acknowledge that the protein film on surface of blood air interface issue may exist; based on literature we estimate this to contribute no more than +0.375 mPa s to viscosity at, or 0.0375 Pa to the stress measurement at shear rates below 100 s-1.)BACKGROUND:Human blood is a thixo-elasto-visco-plastic (TEVP) material that exhibits unique fluctuations in mechanical properties based on physiology, and shear rate. We demonstrate new visual tools to help visualize and characterize these varied mechanical properties. Objective Our objective is to demonstrate contemporary visual and numerical tools to help visualize and characterize the varied mechanical properties of human blood. Methods Using the ARESG2 strain-controlled rheometer with double wall couette geometry and eight human blood donors, with lab test results, elastic and viscous properties are investigated using Series of Physical Processes (SPP) and MITLaos to both analyze and visualize the mechanical signatures of the blood. Results Variations of mechanical properties are shown via SPP generated Cole-Cole plots and MITLaos analysis. These variations are a function of physiological properties of blood on the day of the blood draw based on hematocrit, fibrinogen, cholesterol, triglycerides, and a host of other proteins and constituents. Each rheological experiment with blood is replicated with an analogous experiments with 0.04 wt% xanthan in glycerol, and water to demonstrate that the mechanical properties of the human blood, and its rheological signatures are unique to human blood. Conclusions Human blood is proven to be a TEVP material, as shown on a series of Cole-Cole plots for eight different donors, at two different frequency and strain amplitude combinations. Variations in Cole-Cole plots for each donor are shown. MITLaos average mechanical properties are calculated and shown. Aggregated elastic and viscous projections and a Cole-Cole plot is shown for Donors 1-8, along with 95% confidence interval.