川嶋 大介

Non-invasive hERG channel screening is achieved by integrating electrical impedance tomography (EIT) and extracellular voltage activation (EVA) into a PCB sensor.

<jats:title>Abstract</jats:title> <jats:p>Image reconstruction in electrical impedance tomography (EIT) is a typical ill-posed inverse problem, from which the stability of conductivity reconstruction affects the reliability of physiological parameters evaluation. In order to improve the stability, the effect of boundary voltage noise on conductivity reconstruction should be controlled. A noise-controlling method based on hybrid current-stimulation and voltage-measurement for EIT (HCSVM-EIT) is proposed for stable conductivity reconstruction. In HCSVM-EIT, the boundary voltage is measured by one current-stimulation and voltage-measurement pattern (high-SNR pattern) with a higher signal-to-noise ratio (SNR); the sensitivity matrix is calculated by another current-stimulation and voltage-measurement pattern (low-cond pattern) with a lower condition number; the boundary voltage is then transformed from the high-SNR pattern into the low-cond pattern by multiplying by an optimized transformation matrix for image reconstruction. The stability of conductivity reconstruction is improved by combining the advantages of the high-SNR pattern for boundary voltage measurement and the low-cond pattern for sensitivity matrix calculation. The simulation results show that the HCSVM-EIT increases the correlation coefficient (CC) of conductivity reconstruction. The experiment results show that the CC of conductivity reconstruction of the human lower limb is increased from 0.3424 to 0.5580 by 62.97% compared to the quasi-adjacent pattern, and from 0.4942 to 0.5580 by 12.91% compared to the adjacent pattern. In conclusion, the stable conductivity reconstruction with higher CC in HCSVM-EIT improves the reliability of physiological parameters evaluation for disease detection.</jats:p>

Abstract The assessment method of anisotropic transmembrane transport coefficient vector P of a cell-spheroid under inhomogeneous ion concentration fields has been proposed by combining electrical impedance tomography (EIT) with an ion transport model to evaluate the anisotropic transmembrane transport of ions. An element P_i of P represents the transmembrane transport coefficient of the ith part of the cell membrane, which is assessed by the ion transport model from the average conductivity σ̃_i of the ith extracellular sector reconstructed by EIT. Anisotropic factor H obtained from P_i is introduced, which represents the anisotropic transmembrane transport. To validate our methodology, the inhomogeneous ion concentration fields are generated by injecting two tonicity-different sucrose solutions (isotonic, hypotonic or hypertonic) from both sides of the cell-spheroid. As a result, the inhomogeneous ion concentration distribution due to the anisotropic transmembrane transport is successfully observed from the reconstructed image by EIT. The anisotropic factor H shows that H = 0.34 ± 0.24 in isotonic and hypertonic combination, H = 0.58 ± 0.15 in isotonic and hypotonic combination and H = 0.23 ± 0.06 in hypertonic and hypotonic combination, respectively. To verify the results obtained by our methodology, the fluorescence ratio F [-] of potassium ions around the cell-spheroid is observed under three combinations as same as the EIT measurement. F shows the anisotropic transmembrane transport with the same trend with the EIT results.

<jats:title>Abstract</jats:title> <jats:p>The image reconstruction in electrical impedance tomography (EIT) has low accuracy due to the approximation error between the measured voltage change and the approximated voltage change, from which the object cannot be accurately reconstructed and quantitatively evaluated. A voltage approximation model based on object-oriented sensitivity matrix estimation (OO-SME model) is proposed to reconstruct the image with high accuracy. In the OO-SME model, a sensitivity matrix of the object-field is estimated, and the sensitivity matrix change from the background-field to the object-field is estimated to optimize the approximated voltage change, from which the approximation error is eliminated to improve the reconstruction accuracy. Against the existing linear and nonlinear models, the approximation error in the OO-SME model is eliminated, thus an image with higher accuracy is reconstructed. The simulation shows that the OO-SME model reconstructs a more accurate image than the existing models for quantitative evaluation. The relative accuracy (RA) of reconstructed conductivity is increased up to 83.98% on average. The experiment of lean meat mass evaluation shows that the RA of lean meat mass is increased from 7.70% with the linear model to 54.60% with the OO-SME model. It is concluded that the OO-SME model reconstructs a more accurate image to evaluate the object quantitatively than the existing models.</jats:p>

Abstract Transmembrane ion transport under tonicity imbalance has been investigated using a combination of low frequency-electrical impedance spectroscopy (LF-EIS) and improved ion transport model, by considering the cell diameter d [m] and the initial intracellular ion concentration c_in [mM] as a function of tonicity expressed by sucrose concentration c_s [mM]. The transmembrane ion transport is influenced by extracellular tonicity conditions, leading to a facilitation/inhibition of ion passage through the cell membrane. The transmembrane transport coefficient P [m s⁻¹], which represents the ability of transmembrane ion transport, is calculated by the extracellular ion concentrations obtained by improved ion transport model and LF-EIS measurement. P is calculated as 4.11 × 10⁻⁶ and 3.44 × 10⁻⁶ m s⁻¹ at c_s of 10 and 30 mM representing hypotonic condition, 2.44 × 10⁻⁶ m s⁻¹ at c_s of 50 mM representing isotonic condition, and 3.68 × 10⁻⁶, 5.16 × 10⁻⁶ , 9.51 × 10⁻⁶, and 14.89 × 10⁻⁶ m s⁻¹ at c_s of 75, 100, 125 and 150 mM representing hypertonic condition. The LF-EIS results indicate that the transmembrane ion transport is promoted under hypertonic and hypotonic conditions compared to isotonic condition. To verify the LF-EIS results, fluorescence intensity F [–] of extracellular potassium ions is observed to obtain the temporal distribution of average potassium ion concentration within the region of 3.6 μm from cell membrane interface c_ROI [mM]. The slopes of ∆c_ROI/c_ROI1 to time t are 0.0003, 0.0002, and 0.0006 under hypotonic, isotonic, and hypertonic conditions, where c_ROI1 denotes initial c_ROI, which shows the same tendency with LF-EIS result that is verified by the potassium ion fluorescence observation.

Copper particle has been detected among dominant aluminum particles by in-situ resistance background implemented in conductance-path recognition algorithm (iRB-CPR). The iRB is a particle volume fraction prediction from a resistance background database measured by shifted-four-wire measurement (SRM) in various particle arrangements. The CPR is adopted from a decision tree algorithm to predict the particle conductance path by comparing the real-condition resistances classified by iRB. The selected resistance background is used as a denominator to normalize the resistance measurement by SRM under unknown particle arrangement in the real condition. Finally, Cu is detected by comparing the normalized resistances with the normalized spatial-mean resistance. The iRB-CPR successfully suppress the resistance deviation ratio in the simulation 〈r〉sim 93.8% and experiment 〈r〉exp 73.9%. Moreover, the Cu detection by iRB-CPR satisfies give a low error ES = 6.11% at S = 180 under α = 10%. This research opens a new detection modality as a part of non-ferrous metal particles recovery.

Reconstructing the structural images of human body compartments as a point-of-care imaging could be possible using electrical impedance tomography (EIT) but the reconstructed image deteriorates due to high conductivity contrast &#x03BC; between anomaly and background. In this study, a multifrequency EIT with a ratiometric preprocessing (ratiometric EIT) has been developed in order to minimize &#x03BC; while maintaining high distinguishability without any a priori information. The preprocessing of ratiometric EIT is achieved by extending the framework of ratiometric methods that uses the ratio of two measurement signals. Based on the proposed ratiometric preprocessing, ratiometric frequency-difference adjacent EIT (rfda-EIT) is newly derived. The rfda-EIT is qualitatively and quantitatively evaluated by numerical simulation under the variant conditions of &#x03BC; (= 95%-10%) and experiment with eight subjects&#x2019; calves. As the results, the rfda-EIT scores the area ratio error of subcutaneous adipose tissue (SAT) 17.09% &#x003C; ARESAT &#x003C; 28.13%, the position error of bone tibia 0.14% &#x003C; PEtibia &#x003C; 10.19%, the position error of bone fibula 9.51% &#x003C; PEfibula &#x003C; 1.74%, and the correlation coefficients 0.79 &#x003C; CC &#x003C; 0.91 in the numerical simulation. The total-mean area ratio error &#x003C;ARESAT&#x003E; by the rfda-EIT is lower than the error by the classical frequency-difference adjacent EIT (fda-EIT) from 12.70% to 5.18% in the experiment. Moreover, the true positive rate TPRtibia for the bone tibia detection by the rfda-EIT is increased from 50.0% to 87.5% as compared with the rate by the fda-EIT.

Two equations have been developed from multi-frequency measurements of blood impedance Zb for a simultaneous electrical online estimation of changes in blood hematocrit ΔH [%] and temperatures ΔT [K] in cardiopulmonary bypass (CPB). Zb of fixed blood volumes at varying H and T were measured by an impedance analyzer and changes in blood conductivity σb and relative permittivity εb computed. Correlation analysis were based on changes in σb with H or T at f = 1 MHz while H and T equations were developed by correlating changes in εb with H and T at dual frequencies of f = 1 MHz and f = 10 MHz which best capture blood plasma Zp and red blood cell cytoplasm Zcyt impedances respectively. Results show high correlations between σb and H (R2 = 0.987) or σb and T (R2 = 0.9959) indicating dependence of the electrical parameters of blood on its H and T. Based on computed εb, changes in blood hematocrit ΔH and temperature ΔT at a given time t are estimated as ΔH(t) = 1.7298Δεb (f = 1 MHz) – 1.0669Δεb (f = 10 MHz) and ΔT(t) = -2.186Δεb (f = 1 MHz) + 2.13Δεb (f = 10 MHz). When applied to a CPB during a canine mitral valve plasty, ΔH and ΔT had correlations of R2 = 0.9992 and R2 = 0.966 against H and T respectively as measured by conventional devices.

A sensitive frequency f margin SFM has been determined for quantification of aggregated interstitial protein concentrations Фprot by frequency difference electrical impedance tomography fd-EIT. Impedances of increasing Фprot of albumin-globulin mixtures in phantoms were measured and changes in protein's adjacent f point conductivity Δσadj and loss factor Δε''adj plotted against f to determine a Фprot SFM fsen where σadj and ε''adj change significantly with Фprot. Results show that the Δσadj and Δε''adj dropped rapidly with increase in f up to f = 10 kHz then gradually to f = 100 kHz. The σ and ε” were only sensitive to Фprot as f increased from 1 to 10 kHz. For fd-EIT, optimum reference frequency fref was set at 100 kHz. At fsen = 1 kHz against fref, fd-EIT reconstructed σ due to 30% increase in Фprot with area ratio error ARE = 4.1% and a position error PE = 0.1 [-].

Albumin diffusivity coefficient DaI in imitated porous structure of interstitial space has been estimated by means of the integration of albumin diffusion model (ADM) to electrical impedance tomography (EIT) (iADM-EIT) under five different porosity φ conditions (from φ1 = 0.922 to φ5 = 0.990) for transport phenomena quantification. The iADM-EIT was conducted by applying an iterative curve-fitting between spatio-temporal albumin concentration CaI derived from ADM and spatio-temporal distribution of conductivity difference Δσ reconstructed by EIT. The essential point of the iADM-EIT is the quantification of experimental CIa from Δσ by establishing a constitutive relationship among CIex a, Δσ, and φ. ADM is developed based on Fick's second law implemented in Krogh tissue cylinder. EIT is performed to image the Δσ caused by increase of CIa due to albumin diffusion phenomenon from a capillary to the imitated porous structure. The imitated porous structure is manufactured with agarose gel in a dynamic phantom including a capillary. As a result, the relative albumin diffusivity coefficient (D0a: free diffusivity of albumin coefficient) is increased with the increase of φ in the range from 0.271 to 0.694, which are correspondent to the literature data with percent average relative error δ = 6.83 ± 2.72%.

In-vivoviscoelastic properties have been estimated in human subcutaneous adipose tissue (SAT) by integration of poroviscoelastic-mass transport model (pve-MTM) into wearable electrical impedance tomography (w-EIT) under the influence of external compressive pressure -P. Thepve-MTM predicts the ion concentration distributioncmod(t)by coupling the poroviscoelastic and mass transport model to describe the hydrodynamics, rheology, and transport phenomena inside SAT. Thew-EIT measures the time-difference conductivity distribution∆γ(t)in SAT resulted from the ion transport. Based on the integration, the two viscoelastic properties which are viscoelastic shear modulus of SAT Gvand relaxation time of SAT τvare estimated by applying an iterative curve-fitting between the normalized average ion concentration distribution〈čmod〉(t)predicted from pve-MTM and the experimental normalized average ion concentration distribution〈čexp〉(t)derived fromw-EIT. Thein-vivoexperiments were conducted by applying external compressive pressure -Pon human calf boundary to induce interstitial fluid flow and ion movement in SAT. As a result, the value of Gvwas range from 4.9-6.3 kPa and the value of τvwas range from 27.50-38.5 s with the value of average goodness-of-fit curve fitting R2> 0.76. These value of Gvand τvwere compared to the human and animal tissue from the literature in order to verify this method. The results frompve-MTM provide evidence that Gvand τvplays a role in the predicted value of č_mod.

Plural long short term memory (pLSTM) applying to a multiple voltage-current (mVC) system has been proposed in order to estimate the void fraction α accurately in gas-liquid flows. The pLSTM consists of two LSTMs, one for flow regime identification (fri-LSTM) and the other for void fraction estimation (vfe-LSTM). The fri-LSTM identifies a flow regime q from current vectors i, corresponding to gas distribution, measured by mVC system. Based on the identification result and i, the customized vfe-LSTM to each q estimates α. For training, i are experimentally measured at 36 points of the true void fraction α, which is calculated by the drift flux model. On the other hand, i for test data are measured under 12 points of α. Two parameters of each LSTM, one is sequence length S representing time dependence length considered within the LSTM and the other is the number of LSTM blocks M related to the estimation performance, are optimized so that accurate void fraction estimation is achieved. As a result, p LSTM applying to mVC system achieves a 100% accuracy of flow regime identification and less ±0.00034 standard error of void fraction estimation in liquid single-phase flow, bubble flow, slug flow, and churn flow. Accurate estimation is caused by the fact that p LSTM can consider the time dependence of gas-liquid flows suitable for each flow regime and neglect the effect of the flow regime on i.

Low-frequency impedance-based (LFI) cell discrimination as a novel non-destructive and non-invasive cell discrimination is proposed. LFI cell discrimination discriminates the cell type by considering an ion transport model in cell suspension. Ion transport model in cell suspension is constructed on the basis of Fick's laws of diffusion in the extracellular region under ion permeability P which represents the characteristics of cell type. P is achieved using the ion transport model equation through an iterative curve fitting to an ion concentration in extracellular region obtained from low-frequency impedance which is assumed to be linearly related to the ion concentration in extracellular region. In experiment, the electrical impedance spectra from the frequency of 200 kHz to 2.0 MHz are measured over time during producing ions from intracellular region to extracellular one in cell suspension using an impedance analyzer and an interdigitated array electrode system. As a target cell type, two different cell types based on Medical Research Council 5 (MRC-5), which are different in intracellular component are used. The curve fitting is performed for the low-frequency impedance at 200 kHz at which impedance reflects the ion concentration in extracellular region in order to obtain P of each cell type. As a result, each cell type has its own P. The proposed LFI cell discrimination successfully discriminates the cell type.

© 2020 IEEE. This paper has proposed a new dielectric properties extraction method of cell's complex permittivity ϵ *cell even in cell solutions from the measured impedance Z*sol, exp by GHz electrical impedance spectroscopy (EIS) in the frequency range from 10 MHz to 3 GHz. This new extraction method is composed of the electrical impedance measurement of cell solutions and dispersed medium and the dielectric properties calculation based on a combination of plane wave and transmission line theories. By comparing with ϵ*cell, BH obtained by Bruggeman-Hanai equation, this new method is proved to extract the complex permittivity of cells ϵ*cell in cell solutions successfully from the experimental impedances of yeast cell solutions Z*sol, exp and dispersed medium Z*dis, exp by GHz EIS with the relative error less than 10% in the frequency range from 10 MHz to 3 GHz. Moreover, the conductivity of cell σcell among different concentrations obtained by this method shows the smaller discrepancy than that obtained by Bruggeman-Hanai equation in the frequency range from 1 GHz to 3 GHz. The dielectric properties ϵ*cell and ϵ*cell, BH are brought into a simulation model, respectively. The simulated impedance Z*sol, sim shows a better agreement with the experimental impedance Z*sol, exp compared with the simulation impedance Z*sol, sim, BH which means the dielectric properties ϵ*cell obtained by this new method is accurate for the future research of cell's dielectric properties in the GHz frequency range.

Three-dimensional ion and particle concentrations under hydrodynamic focusing in a Y-shaped square microchannel are numerically simulated to clarify the decrease of the ion concentration along the flow direction within the focused particle stream. The simulation model is theoretically governed by the laminar flow and advection-diffusion equations. The governing equations are solved by the finite volume method. The ion and particle concentration distributions at five cross sections after the confluence of the branch channels are analyzed in 30 cases in which the sheath to sample flow rate ratio Qsh/Qsam and the Reynolds number Re are varied as parameters. The results show that the decrease of the cross-sectional average ion concentration along the flow direction within the particle stream [Formula: see text] is described by the diffusion length during the residence time with a characteristic velocity scale. In addition, the deformation of the particle stream due to inertial effects is described by a scaled Reynolds number that is a function of the flow rate ratio. The simulated particle stream thicknesses are validated by theory and a simple experiment. This paper reveals the relationship between the ion and particle concentrations and the dimensionless parameters for hydrodynamic focusing in the Y-shaped square microchannel under typical conditions.

In situ measurement of hindered settling function Hϕ as a function of particle volume fraction ϕ in a decanter centrifuge has been proposed by periodic segmentation technique in wireless electrical resistance detector (psWERD). The processes to calculate Hϕ has three steps which are (1) segmentation of measured resistance R(z,t) in three settling periods; (2) elimination of the screw conveyor's (SC's) adverse effect; (3) calculation of ϕ which is important to determine the in situ hindered settling velocity uhinins and calculation of the proposed uhinfit from the proposed Hϕ. In the 1st step, R(z,t) are segmented based on the phases of liquid L, screw S, and particle P under three settling periods which are pre settling (pre), transient settling (tran), and post settling (post). In the 2nd step, the segmented R(z,t) is categorized by fourier transfrom (FT) based on the frequency of the liquid fL, screw fS, and liquid-particle fLP phases with a focus on eliminating SC's adverse effect which causes fluctuating R(z,t). In the 3rd step, the ϕz,t is obtained by applying the effective medium theory (EMT) based on the conductivity of each phase which are liquid σ¯L, particle σP, and slurry σLPz,t. Each conductivity is calculated based on the average liquid resistance R¯Lz, the static particle resistance RP under closed-pack particle volume fraction ϕcp, and the slurry (liquid-particle) resistance RLPz,t from the 2nd step. Afterward, the uhinins is obtained from the distribution of ϕ which refers to the length parameter in the settling radius rset. Hence, the uhinins is calculated by time t needed for particle to settle from ϕ0 to ϕcp in tran. The proposed Hϕ is developed by considering the influence of ϕcp and the increasing distribution of ϕ due to the particle settling which is presented by fitting parameters of k and p. Take into account the importance of single particle settling in Stokes settling velocity uSt, the proposed uhinfit is determined by calculating the uSt and fitting parameters in the Hϕ to fit the uhinins. To evaluate the psWERD, a decanter centrifuge was used in the industrial scale experiment by appliying three operational parameters which are types of SC, centrifugal forces G, and the differential speeds ω. Two types of SC which are SC1 and SC2 were used to investigate the effect of G to the in situ Hϕ under constant ω. While SC2 was used to investigate the effect of ω to the insitu Hϕ under contant G. The in situ measurement is conducted in three measurement points z which represents the particle settling condition at different locations. In order to verify the experiment results, simulation on electrical measurement in the boundary of particle sensitivity area APSA of psWERD and on particle settling behavior in centrifugal fields are done by Multiphysic software. As a result, the psWERD is successful in determining the best fitting parameters for the in situ Hϕ with good average root mean square error 〈RMSE¯〉≤10-3. The in situ Hϕ also has a good agreement to the previous work of Hϕ determined in decanter centrifuges with the similar operational condition. Finally, the Hϕ shows the potential for evaluating the in situ separation process in decanter centrifuges under specific operational conditions.

© 2020 Elsevier B.V. This paper presents a near-infrared imaging method to measure the concentrations of acid (HCl and H2SO4), base (NaOH), and produced salt (NaCl and Na2SO4) simultaneously during neutralization in a microfluidic channel. This method is based on spectral variations in the water absorption band observed in the wavelength range 1350–1600 nm. Linear correlation models using three characteristic wavelengths in the band are constructed to convert the absorbance to the concentrations. The images clearly show that at the interface between the acid and base solution streams, the concentrations decrease and salt is produced, diffusing in the transverse direction. The concentration range is 0–2 mol/L and the resolution is <0.1 mol/L. The concentrations were verified by comparison with numerical simulations and quantitative evaluation of influencing factors. From the images, the local production rates of salt were determined, which depended on the flow velocity and temperature. This study indicates the potential of the method for analyses of not only acid–base neutralizations but also other reactions, mixing, and separation between various aqueous components.

We propose a noise elimination electrical impedance spectroscopy (neEIS) system for single cell identification whose characteristics are cell-free clamp structure and cell-position independent calibration. The function of the cell-free clamp structure is to enable a single cell to be freely located into neEIS system. The cell-position independent calibration consists of three steps; impedance measurement, electrode cell constant calculation, and single cell dielectric properties estimation. The cell-position independent calibration enables elimination the influence of noise associated with ions as well as electrical double layer during the measurement process. We demonstrate an application of neEIS system to discriminate three types of MRC-5 human lung fibroblasts; wild type (WT), GFP-fused histone (HT) modification, and GFP transfected (GFPT) MRC-5 cells suspended in a sucrose medium. To further evaluate the neEIS system, we simulated the electrical potential distribution and root means square error of single cell dielectric properties numerically. As a result, we obtained electric potential distribution which clearly characterized the internal change of single cell components. Moreover, we determined that the neEIS system is capable of accurate single cell identification after noises elimination with less than 1.05% average root means square error. Taken together, these results demonstrate that the proposed neEIS system has the potential to improve the performance of biosensors. Thus, this study will bring a new insight into the development of a biosensor system for high accuracy single cell identification as well as inspire the development of a diagnostic device for early fetal lung diseases based on the neEIS system.

© 2020 The Society of Powder Technology Japan Electrical capacitance tomography with airflow injection system (ECT-AIS) has been developed for controlling particle distribution in pneumatic conveyance in order to maintain homogeneous downstream particle distribution εndot+τ with a delay time τ even under inhomogeneous upstream particle distribution εnupt. ECT-AIS is composed of two ECT sensors for monitoring εnupt and for evaluating εndot+τ after injecting airflow. The airflow is injected to the conveyance pipe by activating a solenoid valve of airflow injection system (AIS) to control the homogeneous εndot+τ in the case that the spatial standard deviation of permittivity distribution at the upstream ECT sensor εSDupt which is calculated from εnupt and the spatial mean permittivity 〈εnup〉t is greater than the threshold value δ. With this developed ECT-AIS, three different experiments are performed under different particle loading ratios (ϕ = 0.25, 0.50 and 0.75) with air flow rate Qa = 0.75 kg/s, 0.50 kg/s and 0.25 kg/s. As εnupt is homogeneous, εndot+τ is also homogeneous. While εnupt was inhomogeneous, εndot+τ was homogeneously distributed due to airflow injection. To evaluate the homogeneity of εndot+τ, the spatial mean permittivity 〈εnup〉t in upstream sensor is compared with 〈εndo〉t+τ in downstream sensor and the two results were evaluated with the measured pressures pnupt and pndot. As a results, εSDdot+τ is less than or equal to δ so that 〈εndo〉t+τ is homogeneous after airflow injection. Based on Darcy–Weisbach equation, as the particles are homogeneous, the pressure is lower than that in inhomogeneous distribution. According to the relationship between mean permittivity and pressure, εndot+τ is successfully controlled in homogeneous conditions by ECT-AIS.

© 2020 Elsevier B.V. Particle volume flow rate QPLUG· in plug flow through a cross section of horizontal pipe has been accurately measured by a combination of dual electrical capacitance tomography sensor and plug flow shape model (dECT-PFSM). The plug flow shape model divides the trapezoidal shape of the plug flow into three flow regions which are Tip, Filling, and Tail regions. The plug flow volume VPLUG is estimated by velocity and length which are measured in each region by the normalized permittivity signal changes obtained from the dECT images under the plug flow in the trapezoidal shape. The path time difference of the plug flow ΔtPLUG is also measured. The total volume flow rate of the plug flow is subsequently obtained from the sum of the plug flow volume of the three regions divided by ΔtPLUG. Consequently, the volume flow rate of the plug flow obtained by dECT-PFSM QECT, PFSM· is compared with that of high-speed camera (HSC) as reference and conventional cross-correlation (CC) method. The absolute error Eabs of the proposed method is less than that of the CC method. The dECT-PFSM method is, therefore an affordable noninvasive technique for accurate determination of the volume flow rate of the plug flow.

© Japanese Society of Biorheology 2020. The influence of fibrinogen concentration on blood dielectric properties has been analyzed by GHz electrical impedance spectroscopy (EIS). The complex impedances of native blood and blood with various fibrinogen concentrations Z*blood,exp were measured by a coaxial sensor in the frequency range from 1 MHz to 3 GHz. The complex permittivity of native blood and blood with various fibrinogen concentrations ε*blood were extracted from the Z*blood,exp by equivalent circuit model based on the transmission line theory. The reactance Xblood,native and resistance Rsblood,native of native blood have a peak called characteristic frequency fc at around 300 MHz. At the time t = 0 min just after fibrinogen addition, the relative blood permittivity εblood decreases, conductivities σblood increases and fc shifts to higher frequency with increase of fibrinogen concentrations cfib in plasma. With increment of time, from t = 0 min to t = 12 min, εblood decreases while σblood slightly decreases to time because red blood cell (RBC) aggregation reaction. By comparing the εblood,native of native blood and blood with various cfib, the fibrinogen dissolved in plasma rises the blood permittivity. However, fibrinogen is unable to rise the blood permittivity unlimitedly because of RBC aggregation reaction.

© 1964-2012 IEEE. Enhancement of positive dielectrophoresis (pDEP) particle trapping by a co-occurring fluid flow under an ac electric field in an electrode-multilayered microfluidic device is investigated by three-dimensional particle-fluid flow simulations. The particle motion near one cross section of the microfluidic device is simulated under a zero flow condition by the Eulerian-Lagrangian method incorporating the ac electrothermal effect, thermal buoyancy, and dielectrophoresis. The mean trapping rate under the steady state Rm is evaluated from the simulated number of trapped particles Ntrap for 54 cases with four parameters: electrode excitation pattern, medium conductivity σ, applied voltage φe, and the real part of the Clausius-Mossotti factor Re[K(ω)]. The simulated pDEP velocity in the upper part of the flow channel is validated by an experiment using cell suspension and is fitted so that the non-dimensional velocity error is within 15% of a typical velocity of pDEP. The mean trapping rate Rm is greatly increased by the fluid flow only in the high conductivity and high voltage cases. Regardless of the electrode excitation pattern, Rm increased almost proportionally to the inflow rate into the capture region, where the pDEP force is effective. From a fitted equation of the results, the increase of Rm when Re[K(ω)] = 0.1 to 0.5 is found to be about 20% to 30% of the number of particles transported into the capture regions. The results quantify the enhancement of pDEP trapping by the fluid flow occurring under practical conditions in the device.

© 2001-2012 IEEE. The normalization equation with two correction parameters {beta } and {gamma } is proposed to estimate the void fraction of liquid-gas flow under the condition of unstable liquid conductivity using a multi-electrode voltage-current (me-VC) system. The variation of electrical current value due to change in liquid conductivity of liquid phase is corrected using parameter {beta }. While {gamma } is the gradient correction parameter, which corrects the different variation rate of normalized electrical current affected by liquid conductivity and the void fraction {alpha } in liquid-gas flow. A lookup table for {beta } and {gamma } is created based on the normalized electrical current obtained at four liquid conductivity and six void fraction conditions. From the experimental results, the proposed normalization equation with {beta } and {gamma } shows better performance in estimating void fraction than conventional normalization equation when the conductivity of liquid in liquid-gas flow is unstable. Through the results, it is found that the proposed normalization equation successfully measures the void fraction {alpha } within a 5% error rate.

© 2001-2012 IEEE. Void fraction in gas-liquid flow has been estimated using the artificial neural network (ANN) with electrical current response (ECR) from a voltage-current (VC) system, which measures electrical currents through the combination with eight electrodes attached around a pipe for gas-liquid flow. The ANN model for ECR with the number of neurons {N} =3136 has the lowest relative error and absolute error, respectively, in estimating void fraction of gas-liquid flow, among five different numbers of neurons ( {N} =392, 784, 1568, 3136 , and 6272) on a hidden layer of the ANN model for ECR. With regard to the change in total loss during the training process, the ANN model for ECR with {N=3136} shows good convergence as 28\times 10^{-4} for void fraction estimation in gas-liquid flow compared to other ANN models with different numbers of neurons {N}. In this paper, electrical currents measured by the VC system in the static experiment with eight void fraction conditions are used to optimize the ANN model for ECR in order to estimate void fraction of gas-liquid flow. In the gas-liquid flow with seven void fraction conditions, the optimized ANN model for ECR is applied for void fraction estimation in order that the estimation performance according to the number of neurons on the hidden layer is evaluated.

© 2019 IOP Publishing Ltd. A weighted parameter vector χ norm based on extracellular fluid resistance in the Cole impedance model is hereby proposed in order to compensate for the volatile-distributed current. The volatile-distributed current due to variance in the unknown contact impedance in an electrical impedance tomography (EIT) sensor distorts the ideality of the frequency-dependent behavior of the object of interest, leading to inaccuracy in the reconstructed images. The sources of variance in the unknown contact impedance include the use of electrodes with inconsistent impedance values, electrochemical reaction or the improper attachment of electrodes to the object of interest. χ norm represents the current pathway lengths at zero frequency which reflects the volatile-distributed current, and it is used to determine the source of the measured impedance. The source of the unknown contact impedance can be the background object in the normal physiological condition, an inclusion object in an abnormal physiological condition or systematic error. The new reconstruction methods are derived from the frequency-difference EIT (fd-EIT) and the weighted-frequency-difference EIT (wfd-EIT) using χ norm. The new reconstruction methods are frequency-difference electrical impedance spectro-tomography (fd-EIST) and weighted-frequency-difference electrical impedance spectro-tomography (wfd-EIST). The performance of fd-EIST and wfd-EIST was evaluated by experimental and simulation studies using biomaterials with frequency measurements from f = 500 Hz to f = 100 kHz and the results were compared with those from fd-EIT and wfd-EIT. The results showed that the use of χ norm reduces the root mean square error, position error, ringing and shape deformation. It also increases the ideality of the frequency-dependent behavior, either for the inclusions or the background objects at different frequencies.

© 2013 IEEE. An empirical model is proposed to detect the living cell fraction Φ in a multi-mixed cell solution by micro electrical impedance spectroscopy (EIS) as Φ = -1.46 ψ0 + 1.97. The living cell indicator ψ0 is defined by a quotient of the extrema in the impedance imaginary parts of the detected cell solution's medium, Zextmed , and referenced Zextmedref. The theoretical effectiveness of the model is examined by an electrochemical simulation. In addition, the sensor size versatility is discussed by a comparison experiment that reveals that the sensor size has little effect on the detection result. To support real-time detection, Zextmed and Zextmedref are replaced by the impedance of the cell solution, Zextm, and Zextmref. The versatility of real-time detection is discussed by a medium similarity coefficient η (f) that is defined to explain the effect of replacement. The results reveal the feasibility of the replacement as η > 95 % in the injected current frequency range of ψ 0 by micro EIS.

© 2018 IOP Publishing Ltd. The diffusion coefficients of methanol, ethanol, ethylene glycol, and glucose in water, and their temperature dependence are measured by analysing the simultaneously acquired temperature and concentration images. Simultaneous imaging is achieved using two wavelengths, 1905 nm and 1935 nm, in the ν 2 + ν 3 absorption band of water. In the band, the absorbance at 1905 nm is the most sensitive to temperature, whereas that at 1935 nm is independent of the temperature but strongly dependent on the concentration. To measure the diffusion coefficients, the time evolutions of the diffusion lengths are obtained by fitting the analytical solutions of the two-dimensional steady-state diffusion equation to the transverse concentration profiles in a Y-shaped microfluidic channel. The measured diffusion coefficients and their temperature dependence are verified by comparison with literature values.

© 2016 Institution of Mechanical Engineers. The Mach number and pressure at the outlet plane of a straight micro-tube were investigated numerically for both laminar and turbulent flow cases. The numerical methodology is based on the arbitrary Lagrangian-Eulerian method. The LB1 turbulence model was used for the turbulent flow case. The compressible momentum and energy equations with the assumption of the ideal gas were solved. The computational domain is extended to the downstream region from the micro-tube outlet. The back pressure was given to the outside of the downstream region. The computations were performed for a tube whose diameter ranges from 50 to 500 μm. The average Mach number at the outlet plane of the choked flow depends on the tube diameter and ranges from 1.16 to 1.25. The flow characteristics of the under-expanded gas flow in a straight micro-tube were revealed.

© 2016 IOP Publishing Ltd. This paper presents a simultaneous imaging method of temperature and ethanol concentration of ethanol-water mixtures in microfluidic channels. The principle is based on the facts that the absorbance at a wavelength of 1905 nm is dependent on the temperature of water and that the absorbance at 1935 nm is independent of the temperature but strongly dependent on the molar concentration of water, which is reciprocal to the molar concentration of ethanol in the mixture. The absorbance images at the two wavelengths were acquired alternately, each at 50 frames per second, by an alternate irradiation system and near-infrared (NIR) camera, and then converted to the temperature and concentration images by a linear regression model. The imaging method was applied to a dilute ethanol-water mixture with an ethanol concentration of 0.43 M and water flowing side by side in a temperature-controlled Y-channel. The concentration images clearly showed differences between the mixture and water streams, and that the transverse concentration gradient between the two streams decreased downstream by mutual diffusion. It was also confirmed that the mutual diffusion coefficient increased as the temperature increased. The temperature images showed that uniform distributions were immediately formed due to heat transfer between the fluid and channel materials.

© Institution of Mechanical Engineers 2015. This paper presents experimental results on the friction factor of gaseous flow in a PEEK micro-tube with arithmetic mean roughness of 0.2 μm (relative surface roughness of 0.04%). The experiments were performed for nitrogen gas flow through the micro-tube with 514.4 μm in diameter and 50 mm in length. Three pressure tap holes were drilled on the PEEK micro-tube wall at intervals of 5 mm and the local pressures were measured. The quasi-local friction factor is obtained from the measured pressure differences. The experiments were conducted in the turbulent flow region. The quasi-local friction factor obtained from the present study is compared with those in the available literature and also numerical results. The quasi-local friction factor obtained is 12-20% higher than the value predicted from the Blasius formula.

<p>本論文では，マイクロ流路チップ内において酸・アルカリ水溶液の中和反応より生成する塩濃度を可視化するため，近赤外域の単一波長を利用した新しいイメージング技術を提案する．本イメージング法は，水のν₁+ν₃吸収バンド内にある波長1520 nmの吸収特性を利用する．波長1520 nmは，酸やアルカリ水溶液特有の等吸収点であり，これらの溶質濃度の増減によって吸光度が変化しない．一方，塩濃度に関しては吸収感度があるため，この波長の吸光度測定により塩濃度を見積もることができる．単一波長を利用した本手法を評価するため，T字型マイクロ流路を用いて，(i)水とNaClの混合および(ii) 塩酸と水酸化ナトリウム水溶液の反応拡散の2条件についてNaCl濃度の可視化実験を行った．測定したNaCl濃度は数値解析結果と比較してよく一致しており，提案手法の有効性を示した．</p>

This paper focuses on data reduction of friction factor of compressible fluid flowing through micro-channels. The both pressure and temperature are required to calculate the friction factor of compressible flow. Therefore, in the past data reduction of many experiments, the friction factors have been obtained under the assumption of isothermal flow since temperature measurement of compressible flow in micro-channels is quite difficult due to the experimental technique limitation. The authors find that the temperature of the fluid can be obtained from the pressure under the assumption of one dimensional flow in an adiabatic channel (Fanno flow). In this paper, the temperatures obtained by our proposed equation are compared with results of numerical simulations and friction factors are also compared. © 2014 Elsevier Ltd. All rights reserved.

This paper focuses on temperature rise due to the viscous dissipation in liquids flowing through micro-channels. In the past, equations for the prediction of the temperature rise have been obtained as a function of the friction factor, Reynolds number and Eckert number or a similar form, starting from Navier-Stokes equation and energy equation under the assumption of fully developed laminar flow by researchers. The temperature rises calculated from the equations have been compared with experimental data and the equations have been validated. However, in this paper, a new equation for the prediction of the temperature rise is simply obtained from the first law of thermodynamics without restriction of fully developed laminar flow. © 2012 Elsevier Ltd. All rights reserved.