Shigeru Tada

National Defense Academy of Japan | NDAJ · Department of Applied Physics

Along with the rapid development of cellular biological research in recent years, there has been an urgent need for a high‐speed, high‐precision method of separating target cells from a highly heterogeneous cell population. Among the various cell separation technologies proposed so far, dielectrophoresis (DEP)‐based approaches have shown particular...

This study presented a new method for surface temperature measurement using thermochromic liquid crystals. In the proposed method, the temperatures over the surface of a sheet of thermochromic liquid crystals were measured using the ratio of the spectral intensities of two specific wavelengths less than 450 nm. The measurable temperature range was...

In this study, a new type of dielectrophoretic (DEP) cell-separation device having a parallel-plate flow channel structure was proposed to realize high throughput cell separation. The proposed device consisting of a planar electrode on the top and a planar glass plate, on which interdigitated electrodes arrays were vacuum-deposited, at the bottom w...

Purpose This study aims to propose a contactless and continuous dielectrophoretic cell-separation device using quadrupole electric field. To examine the separation performance, numerical simulations of the electric field in the cross-section of the glass capillary installed in the center of the quadrupole electrode were conducted. Design/methodolo...

We proposed a quadrupole capillary dielectrophoretic (DEP) device, which was a new DEP device enabling invasive and effective cell-separation without contacting the cell suspension to metal electrodes. The device consisted of four brass rods and a glass capillary. The brass rods were glued around the glass capillary to facilitate cell separation by...

In this study, blood flow associated with oxygen transport in the human carotid bifurcation was investigated numerically to assess the effects of bifurcation geometry on distribution and magnitude of the wall shear stress (WSS) and Sherwood number (Sh: dimensionless oxygen wall flux) at the favourable site of atherosclerotic lesion. Three-dimension...

Shock wave therapies require cellular responses. However, how shock waves interact with cells remains elusive. In this study, it was asked whether pressure discontinuities at wave fronts of shock waves are indispensable for evoking cellular responses. With shock wave irradiations, intracellular Ca²⁺ increase was evoked in endothelial cells. This ce...

Low-energy shock waves (LESWs) accelerate the healing of a broad range of tissue injuries, including angiogenesis and bone fractures. In cells, LESW irradiations enhance gene expression and protein synthesis. One probable mechanism underlying the enhancements is mechanosensing. Shock waves also can induce sonoporation. Thus, sonoporation is another...

We developed an insulator‐based dielectrophoretic (iDEP) creek‐gap device that enables the isomotive movement of cells and that is suitable for determining their DEP properties. In the iDEP creek‐gap device, a pair of planar insulators forming a single fan‐shaped channel allows the induction of the isomotive iDEP force on cells. Hence, the cells’ b...

Mitochondria in endothelial cells remodel morphologically when supraphysiological cyclic stretch is exerted on the cells. During remodeling, mitochondria become shorter, but how they do so remains elusive. Drp1 is a regulator of mitochondrial morphologies. It shortens mitochondria by shifting the balance from mitochondrial fusion to fission. In thi...

Dielectrophoresis (DEP) has great potential for cell separation due to its noninvasive and label-free nature. Cells subjected to a non-uniform AC electric field experience DEP force. The magnitude of DEP force and the direction of the force with respect to the field gradient vary dependently on medium conductivity, cell diameter and Re(β), the real...

Various microfluidic devices utilizing the principle of dielectrophoresis (DEP) have been developed to separate, concentrate, and characterize biological cells; however, their performance is still limited by a lack of quantitative characterization. We addressed this limitation by employing a method capable of accurately quantifying a cell's respons...

This paper described the development of measurement method of temperature distribution utilizing thermo-chromic liquid crystal, TLC. In the proposed method, temperature was determined using the ratio of scattered light intensities at narrow band blue wavelengths on TLC. Images of light intensity were captured by two monochrome cameras with band-pat...

We propose a novel, high-performance dielectrophoretic (DEP) cell-separation flow chamber with a parallel-plate channel geometry. The flow chamber, consisting of a planar electrode on the top and an interdigitated-pair electrode array at the bottom, was developed to facilitate the separation of cells by creating a nonuniform AC electric field throu...

When a suspension of polarizable particles is subjected to a gradient AC electric field, the particles exhibit collective motion due to an interaction between the dipole induced in the particles and the spatial gradient of the electric field; this is known as dielectrophoresis. In the present study, the collective dynamics of suspended particles in...

In this study, numerical simulations of suspensions of Al2O3 particles in corn oil at various volume fractions were performed to explore the mechanisms involved in the electro-mechanical behavior of positive polarized particles suspended in an insulated suspending medium traveling through a rotating flow channel while exposed to a nonuniform AC ele...

Shock wave irradiations induce bioeffects including angiogenesis and bone healing. However, physical mechanisms underlying those bioeffects remain elusive. Extracorporeal shock wave treatment (ESWT) is one of well-known shock wave therapies. In ESWT, shock waves destroy kidney stones with cavitation and negative pressures. Energy flux density of sh...

The variability in cell response to AC electric fields is selective enough to separate not only the cell types but also the activation states of similar cells. In this work, we use dielectrophoresis (DEP), which exploits the differences in the dielectric properties of cells, to separate nonviable and viable cells. A parallel-plate DEP device cons...

Hemodynamics can be defined as the part of cardiovascular physiology dealing with the forces that drive the blood circulation in mammalian cardiovascular systems. A cardiovascular system is a series of blood vessels connected to the heart. Pressure generated in the heart propels blood through the system continuously. In this chapter, basic hemodyna...

Mitochondria are subcellular organelles that involved in ATP synthesis, ROS generation, apoptosis and aging, etc. Their morphologies influence cellular activities. When the balance of mitochondrial fusion and fission is lost under the exposure of supra-physiologic cyclic stretches, reactive oxygen species (ROS) are released and cells apoptosis is p...

Fluorescence imaging of cells under mechanical stretching require technical overcomes because cells go out of observation fields. In this study, horizontal movements of cells under mechanical stretching were attempted to be adjusted with fluorescent beads and PIV analysis. As a result, this method realized adjustment when mechanical stretching was...

In the present study, experimental and numerical studies of dielectrophoretic (DEP) flow channel, a type of cell-separation devices that exploits the differences in the dielectric properties of cells, was conducted to design and propose a high-performance cell-separation DEP device. The cell samples used were live and dead cultured budding yeast ce...

Shock wave irradiation accelerates therapeutic effects including angiogenesis. One mechanism underlying those effects is cellular responses evoked by shock wave irradiation. It is known that mechanical stress like shear stress induces intracellular Ca^<2+> increase. In our previous study, it was observed that shock wave irradiation induced the intr...

Visible- and red-light responsive vesicles were prepared by incorporating a ruthenium aqua complex having two alkyl chains on tridentate and asymmetrical bidentate ligands (proximal-2: [Ru(C10tpy)(C10pyqu)OH2]2+, C10tpy = 4'-decyloxy-2,2';6',2"-terpyridine, C10pyqu = 2-[2'-(6'-decyloxy)-pyridyl]-quinoline). The ruthenium complex of proximal-2 with...

Background: The analysis of cell separation has many important biological and medical applications. Dielectrophoresis (DEP) is one of the most effective and widely used techniques for separating and identifying biological species. Objective: In the present study, a DEP flow channel, a device that exploits the differences in the dielectric proper...

This paper describes the expansion of the measurable range of the temperature measurement method using a thermo-chromic liquid crystal. At first, we investigated the relationship between the profile of the spectrum intensity of the scattered light from the surface of the thermo-chromic liquid crystal and the temperature. A halogen light source with...

Cell manipulation and separation technologies have potential biological and medical applications, including advanced clinical protocols such as tissue engineering. An aggregation model was developed for a human carcinoma (HeLa) cell suspension exposed to a uniform AC electric field, in order to explore the field-induced structure formation and kine...

Mitochondria are subcellular organelles that synthesize ATP, generate reactive oxygen species (ROS), and control cellular fates such as apoptosis and aging. Mitochondria generate different amounts of ROS in association with their morphologies. Cyclic stretch is a mechanical stimulation exerted on cells due to arterial pulsation, and induces cells t...

This paper describes the temperature measurement method using thermo-chromic liquid crystal. We investigated experimentally on the relationship between various wavelength spectrum of the scattered light and temperatures. It is found that the white LED light is better than halogen light. The intensity of scattered light is obtained using CMOS monoch...

Cells are continuously exposed to the mechanical stimulus such as the cyclic stretch due to heart beats. The cells are aligned nearly perpendicular to the direction of the cyclic stretch. Recent reports indicate that the pathological levels of cyclic stretch cause apoptosis. The balance of the mitochondrial fusion and fission influences the state o...

The cell-separation analysis has many important biological and medical applications. In the present work, numerical study of dielectrophoretic (DEP) flow channel, a dielectrophoretic devise that exploits the differences in the density and dielectric properties of cells in cell-separation, was conducted to examine the cell-separation performance of...

Mechanical stretches on cells increase traction forces. This increase might involve in several cellular events including mechanosensing. Fluidization is a condition often observed in cells which have been stretched with excessive strain. In those cells, mechanical structures are destroyed and cells lose traction forces. In fluidized cells, it is ob...

In the present study, a novel microfluidic device capable of selectively isolating dead cells from live cells utilizing the difference in their electro-mechanical response to AC electric field was proposed. The device uses a planar electrode and a planar micro-electrode array in a separation flow channel, where the positive dielectrophoretic (DEP)...

In addition with mechanically stimulated cells,intracellular [Ca^<2+>] increase is also observed in neighboring cells.It remains elusive how far those intracellular [Ca^<2+>] increases share prior and posterior pathways.In this study,Ca2+ influxes from extracellular space to cytosol in stimulated cells and neighboring cells were compared to underst...

Shock wave irradiations induce intracellular Ca^<2+> increase in vitro. Shock wave irradiations also induce fluid flow, which could itself induce intracellular Ca^<2+> increase. However, it is obscure whether fluid flow induced by shock wave irradiation involves intracellular Ca^<2+> increase induced by shock wave irradiation. In this study, fluid...

The AC electric field-driven manipulation of suspended polarizable particles has become a major technique in micro- and nano-devices. In the present study, suspensions of cultured HeLa cells in isotonic solution were used to explore the mechanisms underlying the suspension behaviors during exposure to a uniform AC electric field of strength Erms=1....

Blood pressure fluctuations reflect the presence of a variety of dynamic response of the cardiovascular control systems to physiological perturbations to cardiovascular homeostasis. As in most biological processes, these fluctuations exhibit 1/fα characteristic of the power spectrum under physiologic conditions. In recent studies of human blood pre...

Cell manipulation with fluid flow is recently combined with optical tweezers for further precise manipulations. In that combined manipulation system, variety of cell types are manipulated, including yeast cells and stem cells. Although that combined systems allow variety of cells to be positioned precisely, laser power should be limited because of...

In various physical and physiological systems, power spectrum densities (PSD) of temporal sequences appear to be inversely proportion to the frequency. Those systems include the fluctuations of resistances in semiconductors, heart beats and membrane currents. Those inverse proportions of PSD to frequency are so called 1/f noises. One of the mechani...

A two-dimensional (2D) numerical simulation of convective–diffusive transport of LDL in the artery wall, coupled with the wall shear stress gradient (WSSG)-dependent LDL consumption of smooth muscle cells (SMCs) is presented. SMCs are modeled as an array of solid cylindrical pillars embedded in a continuous porous media which represents the interst...

Cytokinesis requires substrate in adhered cells. However, it is obscure whether cells require external forces under the cytokinesis. In this study, external forces applied on cells during cytokinesis were attempted to measure with traction force microscopy. It was investigated whether single MDCK cells divide on polyacrylamide gels and whether FBS,...

Dielectrophoresis (DEP), the motion of polarizable particles in an electric field, has become an important tool for the transport, separation, and manipulation of cells in the field of biomedical engineering. However, DEP-based manipulations require in-channel micro-electrodes or micro-insulators to produce non-uniform electric fields. The present...

1/f'a(0.5<a<1.5) noises are observed in life systems. It is known that the slope of power spectrum density (PSD) in 1/f noises of life systems varies by age and disease. We can expect that 1/f noises are applied to the diagnostic technology. However, the generation mechanism of 1/f noises is not fully disclosed so far. In this study, we propose the...

In addition with medical materials, those involving cells are applied for tissue engineering recently. Cells involved in those medical materials experience physical dynamics after implantations. If the medical material exhibits high elasticity, cells would experience soft physical dynamics. However, if the medical material exhibits low elasticity,...

Purpose – It has been well known that the quantum zero‐point energy (ZPE) cannot be conserved in simulations of atoms and molecules dynamics based on classical mechanics. The purpose of this paper is to examine fundamental issues related to the treatment of quantum ZPE constraint in simulations of atoms and molecules dynamics. Design/methodology/a...

When neutrally buoyant poly alpha olefin particles in corn oil were exposed to a gradient ac electric field generated by a spatially periodic electrode array, these particles experienced the negative dielectrophoresis and instability in all the suspensions of concentration range from 0.01% to 5% (v/v). One critical particle concentration was experi...

We used numerical simulations of a continuous model and the molecular dynamics model to understand the particle instability, formation of island-like structures and existence of one critical particle concentration of 1% (v/v) for formation of island-like structures in the suspension in a gradient AC electric field reported in Paper I. The simulatio...

When an AC electric field is applied to a particle, a dielectrophoretic (DEP) force arises. If that field is inhomogeneous, then the particles experience a DEP force, the frequency response of which is a function of their intrinsic electrical properties. In the present study, the DEP forces exerted between cultured HeLa cells exposed to an AC elect...

During mitosis, sister chromatids are separated by several forces including the pulling force toward two sister centrosomes via microtubules. This pulling force was typically evaluated with laser micro-surgery, which disrupts microtubule structures irreversibly. This irreversible disruption disables long term observation during whole mitosis. In th...

1/f fluctuations, the power spectrum of signals inversely proportional to the frequency, have been observed in various types of physiological systems. However, the mechanism of fluctuations is not fully disclosed so far. In our study, we focused our attention on 1/f fluctuations appear in non-equilibrium ions concentration in cells, and built a phe...

1/f noises, the power spectrum density (PSD) of signals inversely proportional to the frequency, have been observed in various types of physical and physiological systems; e.g. current and heart beat. 1/f noise is suggested to be generated by superimposing stochastic processes. Among stochastic processes, autoregressive process is suitable for anal...

The present study demonstrated that exposure of cultured bovine aortic endothelial cells (BAEC) to fluid flow resulted in nitric oxide (NO) production and up-regulation of intracellular calcium ion concentration ([Ca^<2+>]_i), monitored by fluorescent dyes of DAF2-DA and Rhod2-DA, respectively using a confocal laser scanning microscope. BAEC were e...

This study investigates the oxygen mass transport in the region around the human carotid bifurcation, particularly addressing the effects of bifurcation geometry and pulsatile blood flow on the oxygen transport between the blood flow and artery wall tissue, coupled with the metabolic oxygen consumption and oxygen diffusion in the artery wall tissue...

Theoretical analysis of oxygen reduction reaction (ORR) on cathode Pt(111), Pt3Cu(111), and PtCu(111) surfaces in a polymer electrolyte fuel cell (PEFC) is performed to investigate the ORR mechanisms on Pt(111) and the effect of alloying. From density functional theory (DFT) calculations, we found that the difference in adsorption energy of O2 mole...

The accurate biological function of mechanosensitive (MS) channels is crucial for maintaining the viability of living cells. For instance, in vascular endothelial cells, calcium influx from the extracellular environment into cytoplasm is regulated by stretch-activated channels. However, the mechanism by which cells sense force remains unclear. For...

Effects of concentration of suspensions were studied on long range collective anisotropic interactions among polarized particles in a gradient ac electric field by experiment and simulation. In the 0.01% (v/v) suspension, the particles were just packed in the high electric field regions because the dielectrophoretic (DEP) force on particles dominat...

Molecular dynamics (MD) simulations are performed of neutrally buoyant particles in corn oil in a gradient ac electric field generated by a spatially periodical electrode array. According to the simulation, particle instability exists in the corn oil, anisotropic polarization interactions among the particles have memory, the memory is still kept ev...

In the present study, motion and aggregation of polarizable particles in a suspension were simulated numerically when the suspension was exposed to a spatially non-uniform AC electric field generated by the electrode array in a rotating flow chamber. Particles are dielectric spheres of the diameter d of 89.6 μm and density ρp of 3.75 g/cm3, and sus...

When a dilute suspension of neutrally buoyant poly alpha olefin particles and corn oil is exposed to a highly non-uniform AC electric field generated by a spatially periodical electric electrode array, particles are first transported by dielectrophoresis force to the lower electric field region. However, after these particles enter the lower electr...

Endothelial cells are simultaneously exposed to the mechanical forces of fluid wall shear stress (WSS) imposed by blood flow and solid circumferential stress (CS) induced by the blood vessel's elastic response to the pressure pulse. Experiments have demonstrated that these combined forces induce unique endothelial biomolecular responses that are no...

Thermal development of forced convection in a circular tube filled with a saturated porous medium, subjected to the constant wall heat flux with a step change including the effect of viscous dissipation and the longitudinal heat conduction, has been studied numerically. Numerical computations for various values of the governing independent paramete...

Endothelial cells are simultaneously exposed to the mechanical forces of fluid wall shear stress (WSS) imposed by blood flow and solid circumferential stress (CS) induced by the blood vessel's elastic response to the pressure pulse. Experiments have demonstrated that these combined forces induce unique endothelial biomolecular responses that are no...

A theoretical study of the thermal development of forced convection was performed using a circular tube filled with a saturated porous medium, with constant wall heat flux, and with the effect of viscous dissipation. The solution was obtained using the method of separation of variables. The Sturm–Liouville system was solved for the eigenvalues. Ord...

The present study presents a three-dimensional steady numerical simulation of flow through a model of the bifurcation of the common carotid artery (CCA) into the internal (ICA) and external carotid (ECA) arteries, Flow with large inertia bifurcates at the apex (divider tip) and creates a flow recirculation zone associating with very low wall shear...

Dissociation of free acetonitrile-d3 molecule, CD3CN induced by core level excitation was studied near the nitrogen K-edge by time-of-flight fragment mass spectroscopy. A variety of atomic and molecular fragment cations such as D+, CDn+, C2Dn+, and CDnCN+ were detected using the effusive CD3CN beam. Photoelectron–photoion–photoion coincidence techn...

This study demonstrates that aequorin, a luminescent natural dye, is useful for vascular cell intracellular Ca2+ concentration ([Ca2+]i) determination. A new single-photon counting technique was developed to resolve the effects of fluid flow shear stress on [Ca2+]i in human aortic smooth muscle cells (HASMCs). Confluent HASMCs were grown on petri d...