Masamichi Oishi

Three-dimensional two-component velocity measurement of the flow field induced by the Vorticella picta microorganism using a confocal microparticle image velocimetry technique

Understanding the biological feeding strategy and characteristics of a microorganism as an actuator requires the detailed and quantitative measurement of flow velocity and flow rate induced by the microorganism. Although some velocimetry methods have been applied to examine the flow, the measured dimensions were limited to at most two-dimensional two-component measurements. Here we have developed a method to measure three-dimensional two-component flow velocity fields generated by the microorganism Vorticella picta using a piezoscanner and a confocal microscope. We obtained the two-component velocities of the flow field in a two-dimensional plane denoted as the XY plane, with an observation area of 455x341 mum(2) and the resolution of 9.09 mum per each velocity vector by a confocal microparticle image velocimetry technique. The measurement of the flow field at each height took 37.5 ms, and it was repeated in 16 planes with a 2.50 mum separation in the Z direction. We reconstructed the three-dimensional two-component flow velocity field. From the reconstructed data, the flow velocity field [u((x,y,z)),v((x,y,z))] in an arbitrary plane can be visualized. The flow rates through YZ and ZX planes were also calculated. During feeding, we examined a suction flow to the mouth of the Vorticella picta and measured it to be to 300 pls.

Technology of Automobile and Visualization Studies: In Celebration of the 10th Anniversary of Journal of Visualization

Computer simulation and visualization techniques for automotive studies are reviewed through the history of computer-aided visualization techniques to celebrate the 10th anniversary of Journal of Visualization. Future direction of visualization study is also mentioned through the introduction of up-to-dated numerical visualizations.

Continuous and simultaneous measurement of the tank-treading motion of red blood cells and the surrounding flow using translational confocal micro-particle image velocimetry (micro-PIV) with sub-micron resolution

In this study, a translational confocal micro-particle image velocimetry (PIV) system is introduced to measure the microscopic interaction between red blood cells (RBCs) and the surrounding flow. Since the macroscopic behavior of RBCs, such as the tank-treading motion, is closely related to the axial migration and other flow characteristics in arterioles, the measurement method must answer the conflicting demands of sub-micron resolution, continuous measurement and applicability for high-speed flow. In order to avoid loss of the measurement target, i.e. RBCs, from the narrow field of view during high-magnification measurement, the translation stage with the flow device moves in the direction opposite the direction of flow. The proposed system achieves the measurement of higher absolute velocities compared with a conventional confocal micro-PIV system without the drawbacks derived from stage vibration. In addition, we have applied a multicolor separation unit, which can measure different phases simultaneously using different fluorescent particles, in order to clarify the interaction between RBCs and the surrounding flow. Based on our measurements, the tank-treading motion of RBCs depends on the shear stress gradient of the surrounding flow. Although, the relationship between the tank-treading frequency and the shear rate of the surrounding flow is of the same order as in the previous uniform shear rate experiments, our results reveal the remarkable behavior of the non-uniform membrane velocities and lateral velocity component of flow around the RBCs.

Investigation of Micro Droplet Formation in a T-Shaped Junction Using Multicolor Confocal Micro PIV

This paper aims to investigate a mechanism of microdroplet formation using “multicolor confocal micro particle image velocimetry (PIV)” technique. The present system can measure dynamical behavior of multiphase flow separately and simultaneously. It also enables to identify the interactions between two immiscible fluids. We have applied this system to measure the water droplet formation at a micro T-shaped junction. We have also succeeded in dispersing fluorescent tracer particles into both phases. The interaction between the internal flow of to-be-dispersed water phase and of continuous oil phase is measured as a liquid-liquid multiphase flow. As a result of PIV measurement and interfacial geometry scanning, the relationship between flow structure of each fluid and interfacial geometry is clarified. It indicates that the gap between the tip of discontinuous flow and capillary wall, and interface area play an important role in the flow structure and shear stress on the interface.Copyright

Viscoelastic droplet dynamics under very low interfacial tension in a serpentine T-junction microchannel

Viscoelastic surfactant-laden droplets were generated in silicone oil using a microfluidic T-junction channel device and the droplets dynamics was studied. Surfactant can greatly lower the interfacial tension between the continuous phase fluid and the dispersed phase fluid, and also introduces elasticity to the aqueous solution. The droplets in the confined microchannel experience a steady shear by the continuous phase flow, showing distinct morphological evolvement from those under normal magnitude of interfacial tension and Newtonian fluid nature. It is found that under very low interfacial tension droplet fragmentation (or tail streaming) composing of tiny satellites occurs at the rear of droplet (or upstream of droplet). The production of tails seems to depend on the combination of the capillary number (Ca), flow rate ratio and fluid elasticity (described by Weissenberg number, Wi). This phenomenon demonstrates a new flow regime for aqueous micro-droplets which covered by mobilized, soluble surfactant, indicating such a tail streaming concerns not only the fluid dynamical process, but the properties of the dispersed phase fluid.

Application of vorticella’s feeding mechanism as a micromixer

The microorganism, vorticella, of about 50 mum in diameter was found to be capable of mixing beads in microfluidic channel by energizing vortex with its cilia. Vortex generation and flow velocity around the cell body of a vorticella was experimentally studied using both fluorescents and non-fluorescents microbeads of different size (from 0.5 to 20 mum in diameter). Two vortices in two-dimensional flow (single vortex in three-dimensional space) with a diameter of around 400 mum were observed. An average flow rate of 200 mum/s was measured between the centers of the vortex. The induced flow was also found to be powerful enough to move 20-mum beads. We integrated vorticella and microchannel successfully.

Experimental Study of Swirling Flow of a Viscoelastic Fluid With Deformed Free Surface

An experimental investigation was performed on the swirling flow of viscoelastic fluid with deformed free surface in a cylindrical container driven by the constantly rotating bottom wall. The tested fluid was an aqueous solution of CTAC (cetyltrimethyl ammonium chloride), which is a cationic surfactant. Water, 40ppm, 60ppm and 200ppm CTAC solution flows were tested at Froude numbers ranging from 2.59 to 16.3. PIV was used to measure the secondary velocity field in the meridional plane and the deformed free-surface level was extracted from the PIV images. At a similar Froude number, the depth of the dip formed at the center region of the free surface was decreased for CTAC solution flow compared with water flow. The inertia-driven vortex at the up-right corner in the meridional plane becomes more and more weakened with increase of the solution concentration or viscoelasticity. Through analyzing the overall force balance compared with water flow, the first normal stress difference or the weak viscoelasticity was estimated for the dilute CTAC solution flows.Copyright

On the 3D Structure of Elasticity-Induced Unstable Flow in the Curved Microchannel by Using Confocal Micro-PIV and Polarized Camera

In this paper, the three-dimensional (3D) structures of a micellar solution flow in the curvilinear microchannel have been investigated by means of confocal micro particle image velocimetry (PIV). The working fluid is aqueous solution of CTAC/NaSal (cetyltrimethylammonium / Sodium Salysilate). As the flow rate increases, the flow gradually gets into the irregular motion. It is found that the inside flow seems not completely chaotic, but in a manner of oscillation. To be specific, the flow nonlinearity grows as the flow rate increases, the inside flow shows different structures near the wall region and in the bulk due to the elongation of viscoelastic surfactant. Typically, two sub-streams were twisted together, and their flow directions change at the locations where the signs of geometric curvature change. The oscillation stripes represented the area of high extensional stress in the viscoelastic fluid, and were further identified by using polarized high-speed camera. Moreover, statistics shows that the viscoelastic flow field inside the curved microchannel shares the main features of elastic turbulence.Copyright

Visualization and Measurement of Flow-Induced Dynamic Motion of Red Blood Cells Using Tracking Confocal Micro-PIV System

RBC(Red Blood Cell)s have a biconcave shape with diameters of about 8 μm and thicknesses of about 2 μm like a capsule structure with highly deformable membrane. In arterioles having diameters of less than 100μm, the effect of RBCs becomes pronounced because the scales of the flow and the RBCs become similar. RBCs exhibit the axial migration [1] toward the center of blood vessel. The axial migration leads to non-Newtonian flow behavior such as decrease in flow resistance. The tank-tread motion [2] makes an important role for the axial migration and it is dependent on the shear rate of the surrounding flow, which ranges up to 500 s−1 in arteriole.Copyright

Simultaneous Measurement System for Elastic Biological Wall Motions and Its Inner Flow Motions - Is the Aneurysm for a Disease or for a Self-Defense?

To understand the flow structure interactions (FSI) phenomena between the aneurysm and its inside flows, a new measurement technique has been proposed. An in-vitro test has been carried out for an aneurysm model. The constructed measurement system consists of four-camera system (500fps, 1028 x 1024 pixels), a laser source and a host computer. 4D-PTV(four-dimensional particle tracking velocimetry) technique has been applied for the measurement system. Two cameras are used for capturing the wall motions of the aneurysm, and the other two cameras are used for capturing the fluid motions inside of the aneurysm. All cameras are synchronized for FSI analyses of the aneurysm. For the analyses of the wall motions of the aneurysm, motion tracking algorithm has been constructed. For the analyses of the fluid motions of the aneurysm, volumetric PIV measurements have been carried. From the in-vitro tests for the pulsative input to the aneurysm, it seems that the aneurysm works as the pressure stabilizer as in the mechanical system.