Effect Of PEO/HA On Hemorheology In Microchannels And Discussion On Its Mechanism

Frictional resistance causes a large amount of energy loss when fluid flows through a pipe in the industrial field.Adding some water-soluble long-chain polymer into the fluid at a small dose can significantly reduce the flow resistance.This hydrodynamic phenomenon is known as the Toms effect,and the added polymer is called drag reducing polymer?DRP?.Due to the high-efficiency of the DRP,it has been widely used in the industrial field.In recent years,the application of DRP in the field of biomedicine has also attracted wide attention.Trace amounts of DRP can significantly improve systemic blood circulation,having broad application prospects in the field of cardiovascular and cerebrovascular treatment.In this thesis,we investigated the effects of artificial DRP polyethylene oxide?PEO?and natural DRP hyaluronic acid?HA?on blood rheology in microchannels using a combined experimental,theoretical,and simulation approach.In this thesis,the biocompatible material PDMS was used to produce straight and T type rectangular cross-section microchannels with three different contraction ratios.Two different types of DRPs,PEO and HA,were selected,and the Micro-PIV experiment platform was applied,combined with particle tracking velocimetry?PTV?,Z Project method and lattice Boltzmann simulation to study on the effect of DRPs type,polymer molecular weight,polymer concentration,oxidative degradation of polymers,channel size and structure,shear rate on hemorheology.The red blood cells?RBCs?suspension exhibits non-Newtonian shear thinning fluid characteristics,and the shear viscosity increases with the increasing molecular weight and polymer concentration.RBCs deformability test and erythrocyte sedimentation rate?ESR?results indicate that both PEO and HA can increase RBCs deformability and aggregation.And,oxidative degradation of polymers reduces their ability to act on hemorheology.The flowrate of blood in the microchannels is measured by PTV,and both polymers have significant effects on increasing blood flowrate and wall shear rate.At a low shear rate,PEO is more effective.When the wall shear rate is 1852 s^-1,the maximum blood flow rate of the control group is only 0.39 mm/s.After adding 20 ppm of PEO,the blood flow rate increases to 0.58 mm/s.Under a high shear rate condition,HA is more obvious to increase of the blood flowrate.When the wall shear rate is 3086 s^-1,the maximum blood flowrate of the control group is only 0.45 mm/s,while after adding 80 ppm HA,the blood flowrate rises to 0.74 mm/s.PEO and HA have a significant effect on reducing the cell-free layer?CFL?and increasing blood perfusion.Both PEO and HA can reduce the thickness of the CFL by more than 50%,and the effect of HA on reducing the CFL thickness is more prominent.The addition of PEO-25 ppm/HA-25 ppm to the blood simultaneously results in maximum flowrate and minimal CFL thickness at different shear rates,indicating a synergistic effect.An increase in blood flow rate and a decrease in the thickness of the CFL can increase blood perfusion and improve blood circulation in vivo.