Browsing by Author "Tanaka, Shuji"
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- Axisymmetric PDMS (polydimethysiloxane) microchannels for in vitro haemodynamic studiesPublication . Lima, Rui A.; Oliveira, Mónica S.N.; Ishikawa, Takuji; Kaji, Hirokazu; Tanaka, Shuji; Nishizawa, Matsuhiko; Yamaguchi, TakamiThe current microdevices used for biomedical research are often manufactured using microelectromechanical systems (MEMS) technology. Although it is possible to fabricate precise and reproducible rectangular microchannels using soft lithography techniques, this kind of geometry may not reflect the actual physiology of the microcirculation. Here, we present a simple method to fabricate circular PDMS microchannels aiming to mimic in vivo microvascular environment and suitable for state-of-the-art microscale flow visualization techniques, such as confocal uPIV/PTV. By using a confocal uPTV system individual red blood cells (RBCs) were successfully tracked trough a 75 um circular PDMS microchannel. The results show that RBC lateral dispersion increases with the volume fraction of RBCs in the solution, i.e. with the hematocrit.
- In vitro blood flow in a rectangular PDMS microchannel: experimental observations using a confocal micro-PIV systemPublication . Lima, Rui A.; Wada, Shigeo; Tanaka, Shuji; Takeda, Motohiro; Ishikawa, Takuji; Tsubota, Ken-ichi; Imai, Yohsuke; Yamaguchi, TakamiProgress in microfabricated technologies has attracted the attention of researchers in several areas, including microcirculation. Microfluidic devices are expected to provide powerful tools not only to better understand the biophysical behavior of blood flow in microvessels, but also for disease diagnosis. Such microfluidic devices for biomedical applications must be compatible with state-of-the-art flow measuring techniques, such as confocal microparticle image velocimetry (PIV). This confocal system has the ability to not only quantify flow patterns inside microchannels with high spatial and temporal resolution, but can also be used to obtain velocity measurements for several optically sectioned images along the depth of the microchannel. In this study, we investigated the ability to obtain velocity measurements using physiological saline (PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel (300 μm wide, 45 μm deep) using a confocal micro-PIV system. Applying this combination, measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re = 0.02). Velocity profiles were acquired by successive measurements at different depth positions to obtain three-dimensional (3-D) information on the behavior of both fluid flows. Generally, the velocity profiles were found to be markedly blunt in the central region, mainly due to the low aspect ratio (h/w = 0.15) of the rectangular microchannel. Predictions using a theoretical model for the rectangular microchannel corresponded quite well with the experimental micro-PIV results for the PS fluid. However, for the in vitro blood with 20% hematocrit, small fluctuations were found in the velocity profiles. The present study clearly shows that confocal micro-PIV can be effectively integrated with a PDMS microchannel and used to obtain blood velocity profiles along the full depth of the microchannel because of its unique 3-D optical sectioning ability. Advantages and disadvantages of PDMS microchannels over glass capillaries are also discussed.
- Measurement of erythrocyte motions in microchannels by using a confocal micro-PTV systemPublication . Lima, Rui A.; Ishikawa, Takuji; Takeda, Motohiro; Tanaka, Shuji; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, TakamiDetailed knowledge on the motion of individual red blood cells (RBCs) flowing in microchannels is essential to provide a better understanding on the blood rheological properties and disorders in microvessels. Several studies on both individual and concentrated RBCs have already been performed in the past. However, all studies used conventional microscopes and also ghost cells to obtain visible trace RBCs through the microchannel. Recently, considerable progress in the development of confocal microscopy and consequent advantages of this microscope over the conventional microscopes have led to a new technique known as confocal micro-PIV. This technique combines the conventional PIV system with a spinning disk confocal microscope (SDCM). Due to its outstanding spatial filtering technique together with the multiple point light illumination system, this kind of microscope has the ability to obtain in-focus images with optical thickness less than 1 μm, a task extremely difficult to be achieved by using a conventional microscope. The main purpose of this paper is to investigate the ability of our confocal micro-PTV system to measure the motion of individual RBCs at different haematocrit (Hct) through microchannels.
- Microscale flow dynamics of red blood cells in a circular microchannelPublication . Lima, Rui A.; Nakamura, M.; Ishikawa, Takuji; Tanaka, Shuji; Takeda, Motohiro; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, TakamiThe blood flow dynamics in microcirculation depends strongly on the motion, deformation and interaction of RBCs within the microvessel. This paper presents the application of a confocal micro-PTV system to track RBCs through a circular polydimethysiloxane (PDMS) microchannel. This technique, consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a single particle tracking (SPT) method. By using this system detailed motions of individual RBCs were measured at a microscale level. Our results showed that this technique can provide detailed information about microscale disturbance effects caused by RBCs in flowing blood.
- Tracking red blood cells in a circular PDMS microchannel using a confocal micro-PIV systemPublication . Lima, Rui A.; Ishikawa, Takuji; Tanaka, Shuji; Takeda, Motohiro; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, TakamiThe blood flow in microcirculation is characterized mainly by the flow of red blood cells (RBCs), which may be normal or pathological. This paper presents the application of a confocal micro-P1V system lo track RBCs through a circular polydimelhysiloxane (PDMS) microchannel. This technique, consists o!’ a spinning disk confocal microscope, high speed camera and a diode-pumped solid stale (DPSS) laser combined with a single particle tracking (SPT) software (Mtracki). To show the ability of this system detailed motions o!’ individual RBCs were measured at different haematocrits (Hct): 3%, 14% and 37%. Our results show clearly that this technique can provide detailed information about micro-scale disturbance effects caused by RBCs lo the blood flow.
- Velocity fields of blood flow in microchannels using a confocal micro-PIV systemPublication . Lima, Rui A.; Ishikawa, Takuji; Tanaka, Shuji; Takeda, Motohiro; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, TakamiThe in vitro experimental investigations provide an excellent approach to understand complex blood flow phenomena involved at a microscopic level. This paper emphasizes an emerging experimental technique capable to quantify the flow patterns inside microchannels with high spatial and temporal resolution. This technique, known as confocal micro-PIV, consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser. Velocity profiles of pure water (PW), physiological saline (PS) and in vitro blood were measured in a 100mm glass square and rectangular polydimethysiloxane (PDMS) microchannel. The good agreement obtained between measured and estimated results suggests that this system is a very promising technique to obtain detail information about micro-scale effects in microchannels by using both homogeneous and non-homogeneous fluids such as blood flow.
- Velocity measurements of blood flow in a rectangular PDMS microchannel assessed by confocal micro-PIV systemPublication . Lima, Rui A.; Wada, Shigeo; Tanaka, Shuji; Takeda, Motohiro; Tsubota, Ken-ichi; Ishikawa, Takuji; Yamaguchi, TakamiThis paper examines the ability to measure the velocity of both physiological saline (PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel by means of the confocal micro-PIV system. The PDMS microchannel, was fabricated by conventional soft lithography, had a microchannel near to a perfect rectangular shape (300μm wide, 45μm deep) and was optically transparent, which is suitable to measure both PS and in vitro blood using the confocal system. By using this latter combination, the measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re=0.021). Generally, all the velocity profiles were found to be markedly blunt in the central region mainly due to the low aspect ratio (h/w=0.15) of the rectangular microchannel. Predictions by a theoretical model for the rectangular microchannel have showed fairly good correspondence with the experimental micro-PIV results for the PS fluid. Conversely, for the in vitro blood with 20% haematocrit, small fluctuations were found on velocity profiles.