Browsing by Author "Kaneko, Makoto"

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3D pH MEASUREMENT FOR CELL CULTURE USING CT SCAN
(2017-01-01)
Higashino, Nobuya
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Takayama, Toshio
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Ito, Hiroaki
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Horade, Mitsuhiro
;
Tsai, Chia-Hung Dylan
In cell culture, the pH of culture liquid is one of the most important conditions. However, culture liquid may have pH-gradient due to the activity of cells and change of the environment. In order to confirm the existence of pH-gradient, we propose a method for 3D pH measurement using the color change of phenol red. Using the principle of CT scan, we can measure pH-gradient without contacting culture liquid, and thus, decrease the possibility of contamination. In this paper, we consider the influence of light refraction by a cylindrical vessel, and show that we can measure local pH of culture liquid by light absorbance.
3D pH MEASUREMENT FOR CELL CULTURE USING CT SCAN
(2017-01-01)
Higashino, Nobuya
;
Takayama, Toshio
;
Ito, Hiroaki
;
Horade, Mitsuhiro
;
Tsai, Chia-Hung Dylan
Constrained Adherable Area of Nanotopographic Surfaces Promotes Cell Migration through the Regulation of Focal Adhesion via Focal Adhesion Kinase/Racl Activation
(2018-05-02)
Lim, Jiwon
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Choi, Andrew
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Kim, Hyung Woo
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Yoon, Hyungjun
;
Park, Sang Min
Cell migration is crucial in physiological and pathological processes such as embryonic development and wound healing; such migration is strongly guided by the surrounding nanostructured extracellular matrix Previous studies have extensively studied the cell migration on anisotropic nanotopographic surfaces; however, only a few studies have reported cell migration on isotropic nanotopographic surfaces. We herein, for the first time, propose a novel concept of adherable area on cell migration using isotropic nanopore surfaces with sufficient nanopore depth by adopting a high aspect ratio. As the pore size of the nanopore surface was controlled to 200, 300, and 400 nm in a fixed center-to-center distance of 480 nm, it produced 86, 68, and 36% of adherable area, respectively, on the fabricated surface. A meticulous investigation of the cell migration in response to changes in the constrained adherable area of the nanotopographic surface showed 1.4-, 1.5-, and 1.6-fold increase in migration speeds and a 1.4-, 2-, and 2.5-fold decrease in the number of focal adhesions as the adherable area was decreased to 86, 68, and 36%, respectively. Furthermore, a strong activation of FAK/Racl signaling was observed to be involved in the promoted cell migration. These results suggest that the reduced adherable area promotes cell migration through decreasing the FA formation, which in turn upregulates FAK/Racl activation. The findings in this study can be utilized to control the cell migration behaviors, which is a powerful tool in the research fields involving cell migration such as promoting wound healing and tissue repair.
Experimental Study on Microfluidic Mixing with Trapezoidal Obstacles in a 1000-Fold Span of Reynolds Number
(2019-01-01)
Lin, Xin-Yu
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Ito, Hiroaki
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Kaneko, Makoto
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Tsai, Chia-Hung Dylan
;
機械工程學系
Mixing is important for microfluidic systems and placing obstacles in a flow path for generating advection, or splitting/recombination flows, is a very popular method for enhancing the mixing. In this paper, we present experimental investigations on such microfluidic mixing with four different shapes of trapezoidal obstacles and tested them in a 1000-fold span of Reynolds number (Re). The obstacles have four different base ratios 1, 3, 6 and 9, which indicate the ratios between the upper and lower bases of a trapezoid. Two different dyes, yellow and blue, were used for visualizing and evaluating the performance of mixing. The results show that, when the base ratio is 1, the mixing surprisingly becomes worse with the increase of the flowrate. When the ratio is 3 or 6, the mixing performance is first reduced with the increase of Re and then went through a transition around Re of 10 before it rapidly increases. When the ratio is 9, two transition points were found around Re of 10 and 100, respectively. The work provides useful information for realizing shape-dependent mixing performance, as well as for developing an intelligent lab-on-a-chip system.
INTEGRATION OF FLUCTUATION SPECTROSCOPY INTO A MICROFLUIDIC PLATFORM FOR NOVEL CELLULAR VISCOELASTIC MEASUREMENT
(2018-01-01)
Ito, Hiroaki
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Tsai, Chia-Hung Dylan
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Kaneko, Makoto
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機械工程學系
;
Department of Mechanical Engineering
This paper demonstrates the integration of fluctuation spectroscopy into a microfluidic platfolin, which enables a novel high-throughput measurement of viscoelastic parameters for tm-sized soft objects such as red blood cells (RBCs) flowing in a microfluidic channel. Utilizing high-speed/precise feedback position control of a RBC inside a narrow microfluidic channel, we successfully perfolined fluctuation spectroscopy, which is called flicker spectroscopy, sequentially combined with the conventional constriction-passage method. The result shows implicit correlations between mechanical parameters obtained from these two different measurements, providing indications to full inforrnation of viscosity and elasticity of a RBC.
Inverse Streamline Mapping for Finding an Optimum Medicine Injection Point in Micro Chamber
(2018-01-01)
Takayama, Toshio
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Akai, Takayuki
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Tsai, Chia-Hung Dylan
;
Kaneko, Makoto
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機械工程學系
This paper proposes a new concept of "Inverse Streamline Mapping for Finding an Optimum Medicine Injection Point in Micro Chamber". We search the streamlines from the target chamber to the point in the cross-section at the entrance, so that we can find an optimum medicine injection point. The optimum condition is that all streamlines in target chamber start from the smallest cross-sectional area for a given microfluidic chip. The idea is enhanced by designing the microfluidic channel with the desirable streamline mapping between the target chamber and the cross-section at the entrance. We show that the liquid supplied at a particular point can fully cover the chamber in both simulations and experiments.
LED-CT Scan for pH Distribution on a Cross-Section of Cell Culture Medium
(2018-01-01)
Higashino, Nobuya
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Takayama, Toshio
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Ito, Hiroaki
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Horade, Mitsuhiro
;
Yamaguchi, Yasutaka
In cell culture, the pH of the culture medium is one of the most important conditions. However, the culture medium may have non-uniform pH distribution due to activities of cells and changes in the environment. Although it is possible to measure the pH distribution with an existing pH meter using distributed electrodes, the method involves direct contact with the medium and would greatly increase the risk of contamination. Here in this paper, we propose a computed tomography (CT) scan for measuring pH distribution using the color change of phenol red with a light-emitting diode (LED) light source. Using the principle of CT scan, we can measure pH distribution without contacting culture medium, and thus, decrease the risk of contamination. We have developed the device with a LED, an array of photo receivers and a rotation mechanism. The system is firstly calibrated with different shapes of wooden objects that do not pass light, we succeeded in obtaining their 3D topographies. The system was also used for measuring a culture medium with two different pH values, it was possible to obtain a pH distribution that clearly shows the boundary.
MEASUREMENT OF BOTH VISCOUS AND ELASTIC CONSTANTS OF A RED BLOOD CELL IN A MICROCHANNEL
(2018-01-01)
Kirimoto, Atsushi
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Ito, Hiroaki
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Tsai, Chia-Hung Dylan
;
Kaneko, Makoto
;
機械工程學系
In this paper, we propose a novel measurement of both viscous and elastic constants of a red blood cell (RBC) in a microfluidic channel. Although simultaneous measurement of absolute values of RBC viscosity and elasticity has been difficult in a microfluidic channel so far, here we achieved it using precise feedback cell manipulation inside the microchannel According to deformed shape and theoretically estimated shear force, we first obtained Young's modulus, consistent with that obtained in the previous methods with force sensors. In addition, conducting "Loading examination" for the same RBC in the downstream of the microchannel, we succeeded in the estimation of absolute values of viscous and elastic constants of a RBC.
On-Chip Cell Incubator for Simultaneous Observation of Culture with and without Periodic Hydrostatic Pressure
(2019-02-01)
Horade, Mitsuhiro
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Tsai, Chia-Hung Dylan
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Kaneko, Makoto
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機械工程學系
;
Department of Mechanical Engineering
This paper proposes a microfluidic device which can perform simultaneous observation on cell growth with and without applying periodic hydrostatic pressure (Yokoyama et al. Sci. Rep. 2017, 7, 427). The device is called on-chip cell incubator. It is known that culture with periodic hydrostatic pressure benefits the elasticity of a cultured cell sheet based on the results in previous studies, but how the cells respond to such a stimulus during the culture is not yet clear. In this work, we focused on cell behavior under periodic hydrostatic pressure from the moment of cell seeding. The key advantage of the proposed device is that we can compare the results with and without periodic hydrostatic pressure while all other conditions were kept the same. According to the results, we found that cell sizes under periodic hydrostatic pressure increase faster than those under atmospheric pressure, and furthermore, a frequency-dependent fluctuation of cell size was found using Fourier analysis.
On-chip density mixer enhanced by air chamber
(2018-07-01)
Takayama, Toshio
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Miyashiro, Hiroki
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Tsai, Chia-Hung Dylan
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Ito, Hiroaki
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Kaneko, Makoto
This paper proposes an on-chip density mixer that can achieve even density in a target chamber with a swirling flow enhanced by an air chamber. The system is composed of a main channel, a target chamber where two liquids with different densities are included, an isolated air chamber, and an external vibration pump driven by a piezo actuator at the entrance of the main channel. The air chamber is expected to amplify the vibration owing to structure softening. The amplification would be more pronounced at the resonance frequencies of the structure. We developed the system and conducted experiments. We showed that the swirling motion in the target chamber with an air chamber is stronger than that without an air chamber. We also confirmed that the time resulting in even density is shorter when the pump is driven at a resonance frequency. An air-based virtual valve is introduced for maintaining a constant density in the target chamber. Published by AIP Publishing.
On-Chip Virtual Vortex Gear and Its Application
(2018-01-01)
Takayama, Toshio
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Tsai, Chia-Hung Dylan
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Kaneko, Makoto
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機械工程學系
;
Department of Mechanical Engineering
Simultaneous observation of cell behavior on multiple substrates with different heights
(2017-01-01)
Taniguchi, Tsukasa
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Horade, Mitsuhiro
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Ito, Hiroaki
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Takayama, Toshio
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Tsai, Chia-Hung Dylan
We propose a microscopic system that can perform simultaneous time-lapse recordings for studying cell behavior on different substrates. The microscopic objective lens is controlled up and down so that the focal plane is matched with different heights of each surface. The captured video includes two types of images with a given time interval. Later, the focused image corresponding to each substrate is rearranged every time segment. To confirm the working principle, we show the experimental results for smooth muscle cells (SMCs) by using two different substrates.
Simultaneous observation of cell behavior on multiple substrates with different heights
(2017-01-01)
Taniguchi, Tsukasa
;
Horade, Mitsuhiro
;
Ito, Hiroaki
;
Takayama, Toshio
;
Tsai, Chia-Hung Dylan
VIBRATION BASED VIRTUAL VORTEX GEAR
(2018-01-01)
Miyashiro, Hiroki
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Takayama, Toshio
;
Tsai, Chia-Hung Dylan
;
Kaneko, Makoto
;
機械工程學系
This paper proposes Vibration based Virtual Vortex Gear (V(3)G) that can eventually produce a vortex flow in a micro chamber by pressure vibration. An interesting observation is that a vortex flow can be induced under V(3)G without continuous fluid flow in or out at the entrance of chamber, while it is completely different from our previously discovered Virtual Vortex Gear (V(2)G) where we apply a continuous fluid flow. The experiments have been performed to support the idea. Furthermore, we find that the characteristics of V(3)G is enhanced with an additional air chamber.
Virtual vortex gear: Unique flow patterns driven by microfluidic inertia leading to pinpoint injection
(2018-05-01)
Tsai, Chia-Hung Dylan
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Takayama, Toshio
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Shimozyo, Yuta
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Akai, Takayuki
;
Kaneko, Makoto
An interesting phenomenon that vortices are sequentially generated on a microfluidic chip is investigated in this paper. The direction of every two adjacent vortices is opposite to each other, like a set of gears, and thus is named virtual vortex gear (VVG). Both experiments and computational simulations were conducted in order to make clear the mechanism of VVG. The experimental results show that only the flow from a particular point would form vortices and enter the target chamber. A technique of inverse mapping is proposed based on the phenomenon and it demonstrates that only a pinpoint injection is sufficient to control the contents of a microfluidic chamber. VVG can significantly reduce the volume of chemical usage in biological research and has potential for other on-chip applications, such as mixing and valving. Published by AIP Publishing.