Variations in pulsatile flow around stenosed microchannel depending on viscosity

Abstract

In studying blood flow in the vessels, the characteristics of non-Newtonian fluid are important, considering the role of viscosity in rheology. Stenosis, which is an abnormal narrowing of the vessel, has an influence on flow behavior. Therefore, analysis of blood flow in stenosed vessels is essential. However, most of them exist as simulation outcomes. In this study, non-Newtonian fluid was observed in stenosed microchannels under the pulsatile flow condition. A polydimethylsiloxane channel with 60% stenosis was fabricated by combining an optic fiber and a petri dish, resembling a mold. Three types of samples were prepared by changing the concentrations of xanthan gum, which induces a shear thinning effect (phosphate buffered saline (PBS) solution as the Newtonian fluid and two non-Newtonian fluids mimicking normal blood and highly viscous blood analog). The viscosity of the samples was measured using a Y-shaped microfluidic viscometer. Thereafter, velocity profiles were analyzed under the pulsatile flow condition using the micro-particle image velocimetry (PIV) method. For the Newtonian fluid, the streamline was skewed more to the wall of the channel. The velocity profile of the non-Newtonian fluid was generally blunter than that of the Newtonian fluid. A highly oscillating wall shear stress (WSS) during the pulsatile phase may be attributed to such a bluntness of flow under the same wall shear rate condition with the Newtonian fluid. In addition, a highly viscous flow contributes to the variation in the WSS after passing through the stenosed structures. A similar tendency was observed in simulation results. Such a variation in the WSS was associated with plaque instability or rupture and damage of the tissue layer. These results, related to the influence on the damage to the endothelium or stenotic lesion, may help clinicians understand relevant mechanisms.

Lab-on-a-Chip for Cardiovascular Physiology and Pathology

“…It is important to understand the relationship between the flow behavior and stenosis formation. Hong et al [ 110 ] designed a simulation of stenosis with a microfluidic chip using PDMS and polymethylmethacrylate optic fibers ( Figure 10 A). The main goal of this device was to measure and analyze the fluid velocity profiles and fluid shear stress on the walls inside a stenosed channel.…”

“…The main goal of this device was to measure and analyze the fluid velocity profiles and fluid shear stress on the walls inside a stenosed channel. This was performed using a non-Newtonian water and glycerol fluid solution and Newtonian phosphate-buffered saline (PBS) fluid solution [ 110 ]. This device allowed the study of different fluid flow behaviors and their relationship with fluid shear stress at the stenosis regions.…”

“…This device allowed the study of different fluid flow behaviors and their relationship with fluid shear stress at the stenosis regions. This study revealed a Newtonian fluid with higher viscosities to increase fluid shear stress around the stenosis region ( Figure 10 B), which could subsequently induce the risk for lesion rupture and damage the surrounding tissue [ 110 , 111 , 112 ]. Menon et al constructed a 3D stenosis tunable microfluidic chip (which could mimic the atherosclerosis plaques condition in the blood vessel) using PDMS and 3D air bump technique ( Figure 11 ) [ 8 ].…”

“…Since the effectiveness of medication can vary based on demographics, the ability to test cells from specific demographics is also an important tool for pharmacology [ 10 , 94 , 96 , 101 , 115 , 116 ]. In addition, lab-on-a-chip allows for the simulation of various cardiovascular disease conditions at the cellular level that can mimic behavior at the tissue and potentially the whole organ level [ 7 , 8 , 10 , 31 , 94 , 96 , 101 , 110 , 114 , 115 , 116 ]. Drug screening for cardiovascular disease is another potential application where lab-on-a-chip will no doubt be useful for the future as the lab-on-a-chip testing platform can allow for cellular-based drug toxicity studies [ 101 , 115 ].…”

Hydrodynamics and Heat Transfer Characteristics of a Double Gradient Microchannel Porous Model: Fixed Gradients and Variable Gradients Structures

“…First, a large body of research has been undertaken on the fluid properties. Some researchers were summarized the unique physical phenomena accessible in microscale patterned channels, reviewed the basic kinematics of particles with microchannel structures of inertial microfluidic systems, studied the effect of non‐Newtonian fluid pulsation in microchannel structures on flow, created a random porous structure by randomly arranging cylindrical columns in microchannels to study the migration of non‐inertial particles within the structure, and reviewed the link between microfluidics and materials . Second, numerous investigations have described the heat transfer properties.…”