Fig 1.
(a) Creation of the PDMS stenosed microchannel using a polymethylmethacrylate optic fiber and a petri dish. After combining the sanded optic fiber and petri dish, PDMS was poured into the mold and cured at 85°C. Finally, it was separated into a PDMS polymer, a dish, and an optic fiber; the PDMS stenosed channel was then cut into the desired shape. (b) Illustration of the fabricated PDMS stenosed channel (bottom) and actual image (top) captured using a microscope lens. The microchannel had a 500-μm diameter and 60% severity of stenosis. (c) The experimental setup comprised a light source, an optical microscope with an objective lens at 10× magnification (NA of 0.3), and a high-speed camera. The PDMS channel was mounted on the microscope and illuminated using a 100-W halogen lamp. PDMS, polydimethylsiloxane.
Table 1.
Constants for the Carreau-Yasuda model equation.
μ∞ (viscosity at infinite shear rate), μ0 (viscosity at zero shear rate), λ (time constant), a (Yasuda exponent) and n (power law index).
Fig 2.
(a) Actual images captured using the optical microscope lens for phosphate buffered saline, Fluid 1, and Fluid 2. To identify the width ratios depending on the types of fluids, the flow rates were fixed at 3.5 mL/h for the reference fluid (labelled PBS) and 1.0 mL/h for the samples. The schematic diagram at the right side shows that the reference and sample fluids were injected respectively through each inlet and drained away from the outlet. The region of interest focused on the position where the two different fluids meet; the interface was then developed. (b) Viscosity variation depending on the shear rate of the three samples. The flow rate of the samples was changed from 0.05 to 20 mL/h.
Fig 3.
(a) Velocity vector fields of PBS at certain periods (0, 2, 4, 6, and 10 s) for pulsatile flow with 10-s periods per cycle. (b) Pulsatile inlet velocity distribution in a 3-dimensional plot, which was constructed using the velocity information in the bold black box (Fig 3A). Owing to the repetitive characteristic, the time variable was converted into phase (φ) states; thus, φ = 1 was the period per cycle.
Fig 4.
(a) Contoured velocity vector fields of Fluid 1 at φ = 0, 0.1, 0.2, 0.3, and 0.4. The stenosed wall was at r/D = 0.1, and the opposite wall was at r/D = 0.5. (b) Definition of the x/D variable. D is the diameter of the channel, while x/D is the non-dimensional variable. The value of x/D was determined by the value of the x-coordinate, which was divided by the diameter of the channel when x = 0 was assigned at the center of the stenosis region in the x-coordinate. (c) Velocity profiles of Fluid 1 extracted at a certain phase (φ = 0.2) depending on the positions (x/D = -2, -1, 0, 1, and 2). Each data set (mean ± standard deviation) is obtained from ensemble-average over 5 cycles.
Fig 5.
Contoured vector fields representing normalized velocity at φ = 0.2 and 0.4.
In sequence from left to right, PBS, Fluid 1, and Fluid 2 are classified.
Fig 6.
Simulation results representing contoured velocity fields at φ = 0.2 for PBS, Fluid 1, Fluid 2.
Fig 7.
Normalized velocity profiles at the stenosis region (x/D = 0) of the three samples at φ = 0.2 and 0.4.
The samples were (a) PBS, (b) Fluid 1, and (c) Fluid 2. The normalized diameter (r/D) indicates the stenosed wall side at r/D = 0.1 and the opposite wall side without stenosis at r/D = 0.5. Each data set (mean ± standard deviation) is obtained from ensemble-average over 5 cycles.
Fig 8.
Normalized velocity profiles at the peak phase velocity (φ = 0.2) of PBS, Fluid 1, and Fluid 2.
The points were extracted at the (a) pre-stenosis (x/D = -2) and (b) post-stenosis (x/D = 2) regions. As a reference, the parabolic profile is presented in a gray line. The value of 0.0357 in (a) indicates the position of the maximum value in the PBS profile. PBS, phosphate buffered saline. Each data set (mean ± standard deviation) is obtained from ensemble-average over 5 cycles.
Table 2.
Maximum velocity values (mm/s) of three samples at the stenosis apex (x/D = 0), pre-stenosis (x/D = -2) and post-stenosis (x/D = 2) for φ = 0.2 and 0.4.
Fig 9.
(a) Normalized profiles for the WSR and WSS depending on the phases (φ = 0.0–0.4), which are averaged for the stenosed wall and the opposite wall. PBS, Fluid 1, and Fluid 2 in sequence from left to right. (b) WSS distributions in the three samples: PBS (red), Fluid 1 (blue), and Fluid 2 (green) at the pre- and post-stenosis regions (x/D = -2 and 2). Each data set (mean ± standard deviation) is obtained from ensemble-average over 5 cycles.
Table 3.
Variations in WSR and WSS at the downstream of stenosis for three samples.
Fig 10.
Simulation results representing WSS at φ = 0.0 and 0.2 in 3-demensional channel surface.
In sequence from left to right, PBS, Fluid 1, and Fluid 2 are classified.
Fig 11.
The distributions of the WSS for the stenosed wall along the flow direction according to the PBS, Fluid 1, and Fluid 2 (Simulation results).