Transient viscoelastic behavior of blood

Abstract

The dynamic rigidity modulus G′ and loss modulus G″ of horse and bovine bloods were determined over a wide range of hematocrit at 1 Hz after imposing the steady shear of 66 sec⁻¹ for 1 min. At hematocrits below about 80% the value of G′ for horse blood gradually decreased with time after the initial increase. The rate of decrease of G′ showed maxima at hematocrits around 25 and 55% respectively. At high hematocrits above 80% no time variation of G’ was observed.

The values of G′ and G″ for bovine blood were much smaller than those for horse blood. No time variation of G′ and G″ for bovine blood was observed at any hematocrits. These observations indicate that changes in G′ with time at hematocrits below 50% are mainly due to the formation of rouleaux network in blood and the subsequent formation of the nonhomogeneous assembly of rouleaux like a pattern of islands in sea. At hematocrits between 50 and 80%, the time variation of G′ reflect the change of the aggregation structure of closely packed red blood cells from nonequilibrium state to equilibrium one. At high homatocrits above 80%, G′ mainly reflect the deformability or stiffness of packed red blood cells rather than the interaction between red blood cells.