Biological and physical properties of whole human blood

The whole human blood is composed of a cellular part (red blood cells, white blood cells, and platelets), and a liquid part (plasma), which consists of 92% water²².Red blood cells are the most abundant, they represent 97% of the volume of the bio-colloidal matter. Their volume percentage in the blood is given by the hematocrit level (hct). This latter varies between 38% and 50% for a healthy person. Outside the human body, blood naturally coagulates and forms clots. During this process, some components of the plasma will be consumed, and it becomes serum.

The whole human blood is a complex non-Newtonian fluid that can be considered as a colloidal suspension²³. It is characterized by a shear-thinning behavior, where its dynamic viscosity decreases with the increase of the shear rate. At shear rates higher than 100 s-1, blood behaves like a Newtonian fluid with a dynamic viscosity equal to 4 mPa s at a temperature of 37∘C. The blood viscosity depends on the measurement method²³, temperature^23,24, and hematocrit level^23,25. Harkness and Philips^23,24 reported a decrease of 3% per 1∘C of the dynamic viscosity with the increase of the temperature. However, the increase in the hematocrit level causes an increase in the dynamic viscosity, which is greater at low shear rates. Although, the serum has a Newtonian behavior with a constant value of dynamic viscosity at any value of the shear rate, which is equal to 1.23 mPa s under a temperature of 37∘C.

The surface tension of whole human blood and serum are described by a linear equation as a function of temperature in the range of 20∘C to 40∘C²⁶:

For whole blood

For serum

where σ, represent the surface tension on N/m, and T,represent the temperature on ∘C.