Research Areas

Diagnosis of Biological Flows & Biomimetics

Hemodynamics and vascular diseases

Helical vascular graft for stenotic flow

The effect of swirling flow on flow structure at the post-stenosis in pulsatile flow condition (Jet flow with recirculation was developed)
The effect of the swirling flows on the vortex residence time ratio at the post-stenosis. The vortex residence time ratio at (a) Re = 410, (b) 609, and (c) 814. Dotted circles indicate the high P at near wall region. (d) Axial and (e) radial distributions of normalized vortex residence time ratio.
The effect of swirling flow on vortex formation
Variations of the effective torsion curve for various helical curvatures

The swirling flow in a helical graft has beneficial influences on a disturbed flow structure such as stenotic flow. The characteristics of swirling flows generated by helical tubes with various helical pitches and curvatures were investigated.

Swirling flow in the anastomosis

WSS distribution on phantom model depending on swirling intensity (S=0, 0.3, 0.45, 0.6)
Effect of pulsatile swirling flow on the velocity field (x-directional velocity contour map with streamlines)
Variations in the normalized WSS distribution
Vorticity contour map at downstream

Pathological fluid-dynamic characteristics in a 45°end-to-side anastomosis were experimentally investigated using a particle image velocimetry.

Hemodynamics in tandem stenosis

Comparison of mean velocity fields in tandem stenosis with interspacing distance L=3D (upper) and 10D (lower)
The lengths of the recirculation increase with decrease in interspacing distance L
Flow fluctuation developed by proximal stenosis affect to flow around distal stenosis in L=3D condition
Formation of recirculation flow is restricted when L=3D → Flow between two stenosis is focused on the central region

Flow characteristics in tandem stenosis structures were investigated. Interspacing distance between two stenosis and severity of each stenosis affect to flow structures.

WSS-related atherosclerosis in zebrafish

Angiogram of a developing zebrafish at approximately 15 days post-fertilization (dpf).
Length of each section: 460μm
Pulsatility of blood flow at each vessel
WSS distribution at each vessel
Blood flow characteristics in zebrafish disease model
(mean velocity contour map)
Relation between WSS and lipid deposit (Zebrafish(15dpf, fli1:EGFP))

→ Most lipids are deposited in blood vessels with low WSS
Hyper-cholesterol diet (HCD)
→ Cholesterol(4%) + cholesteryl BODIPY 542/563(1%)
→ Most lipids are deposited at veins 3, 4, 5 (caudal vein)

The relation between wall shear stress and cholesterol deposit in blood vessels was revealed in hypercholesterolemic zebrafish model.

Flow measurements using 4D MRI

Schematic representation of velocity and turbulence quantification using 4D PC-MRI
Representative helical flow pattern in the ascending aorta
Velocity distributions through stenotic model measured at various VENC parameters
Effects of multi-VENC overlapping on visualization of velocity vector field

The multi-VENC overlapping method was beneficial for analyzing the low velocity flow structure of the flow field with high velocity dynamic range

Microfluidics for hemorheology

Ultrasonic imaging method to measure erythrocyte aggregation. Quantitative evaluation of aggregation index according to dextran
ESR measurement method. Quantitative evaluations of λESR
Variation of the number of RBCs in an aggregate according to dextran concentration in blood samples
Speckle analysis method to measure erythrocyte aggregation

4 indices from hybrid ex vivo rat experiment can be utilized to diagnose hemorheological diseases; diabetic mellitus

Diagnosis of biological flows & biomimetics: AI-based analysis of 3D position and orientation
of red blood cells using a digital in-line holographic microscopy

DHM setup for acquiring holograms of RBCs
Formaldehyde-fixed RBCs immobilized in a PDMS matrix are attached to a 4-axis stage to precisely manipulate their 3D orientation.
Deep learning network
CNN-based data augmentation and regressions analysis
Data augmentation
RBC holograms with various out-of-plane angles are augmented using mirror symmetry and CAE.
Hologram analysis
3D positions and orientations of RBCs are extracted from a single 2D hologram.