Naoto Kakuta

Tokyo Metropolitan University | TMU · Mechanical Systems Engineering

Monitoring blood glucose levels is essential for patients with diabetes. In the previous study, blood glucose measurement has developed using near-infrared (NIR) imaging, we have found that the accuracy obtained by machine learning based model was reduced by adjustable positioning of the experimental setup and preprocessing techniques of the image....

Rigorous humidity control is required in various industrial fields because water vapor in the air affects the quality of industrial products, food stuff, and others. We have developed a near-infrared imaging system that can determine the temporal and spatial variations of water vapor in an open space. To improve the accuracy or concentration resolu...

This research proposes a near-infrared (NIR) thermal measurement method for investigating thermodynamics on the electrode potential at near interface of electrode during electrochemical reactions. The absorption spectrum of zinc aqueous solution in within the v1 + v2 + v3 water absorption band was characterized with zinc concentration. This techniq...

This study proposes a method for the concurrent visualization and measurement of three-dimensional (3D) temperature and flow fields in water, where a thermal plume arises from a small heat source. This method is based on near-infrared (NIR) absorption imaging with a two-orthogonal-direction telecentric system at a wavelength of 1150 nm. The acquire...

This paper reports on the application of a near-infrared (NIR) imaging system for visualizing heat transfer dynamics from a bulk gadolinium (Gd) sample to the surrounding water during the magnetization/demagnetization process of the magnetocaloric effect (MCE). The suggested approach relied on the spectral variation in water absorption band at 1150...

Preheating is important to improve the mechanical properties of nickel-based superalloys processed by additive manufacturing. The microstructure of IN718 was found to be influenced by the preheating temperature. Different preheating temperatures affect mechanical properties by changing microstructures. This work aims to clarify the thermal behavior...

Base plate preheating is a relatively new strategy to influence the mechanical properties and microstructure of IN718. Base plate preheating was studied to reduce Niobium (Nb) segregation in the interdendritic region of IN718 superalloy and to improve mechanical properties through the laser powder bed fusion (L-PBF) process. Here, we compared exper...

To achieve the in-situ imaging of reaction-diffusion phenomena during aqueous acid-base reactions, regression models constructed based on near-infrared (NIR) spectroscopic data measured using Fourier transform infrared spectroscopy were transferred to the image construction of HCl, NaOH, and NaCl concentrations through multivariate calibration stan...

The near-infrared (NIR) imaging of aqueous acid-base reaction using concentration regression models, wavelength selection algorithms, spectra transfer, and fitting is presented. The near-infrared spectra and concentration regression proposed methods of each acid, base and salt were converted into near-infrared images of concentration and diffusion...

This study visualized heat transfer from small heat sources to water using a near-infrared (NIR) imaging method based on the temperature-dependence of water absorption coefficient at a wavelength of 1150 nm. The NIR absorbance images of a 10-mm-thick water cell, at the bottom of which a 9 mm x 9 mm x 5 mm fin heat sink with an inductively-heated pl...

Herein, the evolution of initial thermal plumes (TPs) from small heating plates in water was investigated using near-infrared (NIR) imaging. The imaging system comprised a telecentric uniform illumination system and an NIR camera. The system employed the temperature dependence of the absorbance of water at a wavelength of 1150 nm for the measuremen...

Rigorous humidity control is required in some industrial and research fields because water vapor in the air affects the quality, hygiene, and stable operation of industrial products, foodstuff, and others. In order to identify the source of water vapor and evaluate its inflow and outflow, we have developed a near-infrared imaging system that can de...

This study presents a method for the simultaneous measurement of three-dimensional (3D) temperature and flow fields in water where a thermal plume arises from a small heat source. This method is based on the near-infrared (NIR) absorption imaging with a two-orthogonal-direction telecentric system at a wavelength of 1150 nm. The acquired images of e...

This study proposes a near-infrared (NIR) imaging method for two-dimensional distributions of water vapour (WV) in the open air. A wavelength of 1872 nm, at which the dependence of the absorption coefficient on the WV concentration is the largest in the ν 2 + ν 3 band of water molecules, was employed for imaging. The measurement system was a star i...

The near-infrared (NIR) absorption spectra of aqueous acid, base, and salt solutions were analyzed to construct the database of concentration regression models for chemical imaging. The spectra of the solutions from 0.0 mol/L to 3.0 mol/L at room temperature were measured using quartz cells with optical path lengths of 1 mm and 0.1 mm for the wavel...

This study proposed a method for reconstructing three-dimensional (3D) non-axisymmetric temperature fields in water formed by mixed convection surrounding a small heating sphere. The proposed method is based on the temperature dependence of the absorption coefficient of water at a wavelength of 1150 nm in the near-infrared (NIR) region. The absorba...

In the imaging of chemical reactions using near-infrared absorbance characteristics, the problem is that the regression model constructed based on the spectrum obtained by the spectroscope cannot be applied to the absorbance image by an actual imaging system. In this study, we corrected the mismatch of spectral information between instruments using...

The near-infrared (NIR) absorption spectra of aqueous acid, base, and salt solutions were analyzed to construct the database of concentration regression models for chemical imaging. The spectra of the solutions from 0.0 mol/L to 3.0 mol/L at room temperature were measured using quartz cells with optical path lengths of 1 mm and 0.1 mm for the wavel...

The near-infrared region of the aqueous acid-base reaction of formed salts (NaBr, KBr, KCl, and NaCl) by neutralization between 1400-1500 nm (OH band) at microchannels was modeled experimentally and numerically. In this study, aqueous acids (HCl and HBr) and bases (NaOH and KOH) of the same molarity were injected simultaneously in a y-shaped microf...

It is necessary for diabetic patients to measure blood glucose levels with blood sampling several times a day. Thus, non-invasive blood glucose sensors have been required to avoid the patients’ psychological and physical stress and the risk of infection. However, for non-invasive techniques proposed so far such as near-infrared (NIR) spectroscopy,...

Quantitative understanding of the concentration profiles of liquid solutions in microfluidic chips is important for chemical reaction analysis. In this study, the concentration profiles of H2SO4, NaOH and Na2SO4 in the neutralization reaction were visualized simultaneously using the near-infrared (NIR) absorption imaging technique with three wavele...

Water vapor, which is universally present in the air, has various adverse effects on industrial products and food materials. Currently, moisture concentration is measured by a humidity sensor at a fixed point in a space; however, to measure and control the moisture distributions, streams, and sources, a water vapor visualization/imaging system is r...

The effect of an enclosure shape on natural convection from a point-like heat source in water is investigated using a near-infrared imaging technique. This method is based on the temperature dependence of the absorption coefficient of water at a wavelength of 1150 nm. In the experiment, a 1-mm-diameter steel sphere inside a water cuvette with a V-s...

To measure the glucose concentration in human skin using near-infrared (NIR) light, we investigated the NIR absorption spectrum of aqueous glucose solutions and selected two characteristic wavelengths: 945 nm and 1200 nm. The two-wavelength rays were incident on the skin and transmitted-reflected light was detected by a 16-channel photodiode (PD) a...

Heat transfer characteristics on natural convection from a heating plate in water are investigated using a near-infrared (NIR) imaging technique. The principle of this method is based on the temperature dependence of the absorption coefficient of water at the wavelength of 1150 nm. In the experiment, rectangular and circular heating plates with a c...

A three-dimensional model for additive manufacturing by selective laser melting (SLM) of powder bed with application to nickel-based alloy IN718 is presented. In this research, the thermal properties of the material and a moving Gaussian laser heat source based on an exponential decay of Beer-Lambert law are taken into account in the calculation. I...

Natural convection around a 1-mm-diameter heated sphere in water were investigated by using a two-directional near-infrared absorption imaging method that can measure simultaneously the temperature and flow fields. This method is based on the temperature dependence of the absorption coefficient of water at the wavelength of 1150 nm. The results ind...

This paper presents a method for measuring simultaneously three-dimensional (3D) temperature and flow fields in water formed by natural convection surrounding a small heating sphere. The main principle is based on the temperature dependence of the absorption coefficient of water at the wavelength of 1150 nm, which is the most temperature-sensitive...

A method to measure simultaneously non-axisymmetric three-dimensional temperature and flow fields in water surrounding a 1-mm-diameter heated sphere is presented. This method is based on the temperature dependence of the absorption coefficient of water at the wavelength of 1150 nm. The temperature profiles are determined by applying the non-axisymm...

This paper presents a method for measuring simultaneously non-axisymmetric three-dimensional (3D) temperature and flow fields in water formed by free convection surrounding a 1-mm-diameter heated sphere. This method is based on the temperature dependence of the absorption coefficient of water at a wavelength of 1150 nm. In the experiment, two-dimen...

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 corr...

We investigated the effect of plasma discharge and magnetic field on the near-infrared absorption spectrum of glucose aqueous solution. The experimental results for the plasma discharge showed a decrease in the absorbance at and near the wavelength of 1450 nm. The possible causes of the spectral change were a change in liquid properties or the brea...

The reaction-diffusion phenomenon between HCl and NaOH in the microchannel was visualized. The wavelength used for visualization was selected from the distribution of regression coefficients by principal component regression analysis, and a regression model was created for simultaneous imaging of three components, HCl, NaOH, and NaCl. For multiple...

In recent years, blood glucose patients are increasing year by year. However, the most widespread measurements are taken by blood sampling, which has struggled many people and the demand for a non-invasive blood glucose measurement device is increasing. Therefore, in this study, we aimed at non-invasive glucose measurement, and examined whether it...

As water vapor in air adversely affects the quality of industrial products and food, the water vapor distribution and generation in a specific spatial region is required to be measured and evaluated. However, it is impossible for conventional measuring instruments to display the water vapor distribution or to identify the source and flow of water v...

This paper presents an experimental method for measuring the water temperature near micro-magnetic particle (MMP) layers in a fluidic channel under induction heating. This method is based on the temperature dependence of the spectrum of the ν1 + ν3 absorption band of water in the near-infrared (NIR) region. The absorbance images at the wavelength o...

This paper presents a method for measuring simultaneously non-axisymmetric three-dimensional (3D) temperature and flow fields in water formed by free convection surrounding a 1-mm-diameter heated sphere. This method is based on the temperature dependence of the absorption coefficient of water at a wavelength of 1150 nm. In the experiment, two-dimen...

The reaction and diffusion phenomenon of HCl and NaOH in the microchannel was visualized.The wavelength to be used for visualization is narrowed down by the stepwise method, and the regression model for performing simultaneous three-component imaging of HCl, NaOH, and NaCl is created by selecting it based on the R-square with corrected degrees of f...

This paper introduces a new technique for temperature measurement of water dynamics fluid near magnetic particles in a microfluidics system. A magnetic fluid is driven to the microfluidic channel, and the magnetic particles form an aggregate on the channel wall by a strong external permanent magnet. Until achieving a certain thickness of particles,...

Near-infrared absorption spectra of H2SO4，NaOH，and Na2SO4 aqueous solutions were measured and analyzed to construct a linear regression model for the simultaneous measurement of their concentrations. Three characteristic wavelengths were selected by principal component analysis, and the absorbances at the wavelengths were used as explanatory variab...

Measurement of three-dimensional distributions of micro-particles is expected to be used for investigations of particle dispersion in media and fluid characteristics in microfluidic channels. This study proposes a near-infrared method to measure micro-particle distributions in water based on the absorption spectroscopic characteristics of water; i....

In order to measure glucose concentration in human skin using near-infrared (NIR) light, we investigated the NIR absorption spectrum of glucose aqueous solutions and selected three characteristic wavelengths: 1165, 1380, and 1600 nm. White optical phantoms made by mixing gelatin, intralipid, glucose, and water were used as measurements samples. The...

This paper presents a method based on the temperature dependence of the absorbance of water at the wavelength of 1150 nm to reconstruct the temperature distributions of water around a 1-mm-diameter heated sphere. Two-dimensional images of the absorbance, which is the transverse projection of the absorption coefficient of water, were acquired by a n...

We report a new experimental method for the temperature measurement of water near micro-magnetic particles (MMPs) in microfluidic channels under induction heating. This technique is based on the temperature dependence of the absorption coefficient of water at the wavelength of 1412 nm. We measured the absorbance distributions of water in a PDMS/gla...

This paper presents a method of reconstructing transient, three-dimensional axisymmetric temperature fields in water formed by laminar free convection from a small heating sphere. This method is based on the temperature dependence of the water absorption coefficient at a near-infrared wavelength of 1150 nm. The horizontal line profiles of the absor...

Prediction and measurement of temperature fields formed by a small heat source inside liquid are important for various thermal applications such as inductive heating of magnetic particles, crystal growth, laser heating, etc. However, as local temperature differences cause natural convection in many cases, the temperature field becomes complicated,...

Measurement of three-dimensional distributions of micro-particles is expected to be used for investigations of particle dispersion in media and fluid characteristics in microfluidic channels. This study proposes a near-infrared method to measure micro-particle distributions in water based on the absorption spectroscopic characteristics of water; i....

For design and evaluation of microfluidic applications, it is important and required to measure concentration distributions of molecules/ions during chemical reactions in microfluidic channels. This paper presents an imaging method of acid-base neutralization reactions, based on the spectral characteristics of the near-infrared absorption band of w...

This paper presents the near-infrared temperature measurement of water near nano-magnetic particle (NMP) clusters heated inductively in the microfluidic channel. This measurement technique is based on the temperature dependence of the absorption coefficient of water. To the bottom of a microfluidic channel in which water flowed, NMPs were aggregate...

In order to measure glucose concentration in human skin using near-infrared (NIR) light, we investigated the NIR absorption spectrum of glucose aqueous solutions and selected four characteristic wavelengths: 945, 1200, 1350, and 1600 nm. A supercontinuum light source with acousto-optic tunable filter and a light-emitting diode were used as the ligh...

Prediction and measurement of temperature fields formed by a small heat source inside liquid are important for various thermal applications such as inductive heating of magnetic particles, crystal growth, and laser heating. However, as local temperature differences cause natural convection in many cases, the temperature field becomes complicated, w...

This paper summarizes a principle and an imaging device for near-infrared (NIR) absorption imaging method developed for microfluidic chips. The NIR absorption imaging method provides temperature and concentration images using the correlation between temperature or solute concentration and the vibration mode of water molecule. By performing image ca...

This paper presents a determination method of heat production rates in a 1-mm-diameter magnetic sphere at different positions in a magnetic field. In this method, three-dimensional radial temperature distributions of water around the sphere were obtained by the inverse Abel transform of two-dimensional radial profiles in absorption images at a wave...

For the design and evaluation of microfluidic applications, it is important to measure concentration distributions of target substances in liquid and to quantify their generation or reduction during chemical reactions. We have thus developed a concentration imaging method for aqueous solutions, based on the near-infrared (NIR) absorption characteri...

Analyses of substances by plasma is one of the developing techniques. Analyses using plasma have problems that need a vacuum device and a large amount of samples. We invented an electrode construction which generates plasma combined corona discharge generating sustainable in the ambient air and barrier discharge to approach to a dielectric to solve...

This paper is indicated using of near-infrared temperature imaging technique to investigate several types of samples containing micro-magnetic particles for hyperthermia and medical purposes. A near-infrared temperature imaging technique based on the temperature dependence of the absorption coefficient of water at a wavelength of 1412 nm was used....

Since magnetic particles are remotely heated by an external alternating magnetic field, they have received a lot of interest to be used for local heating in various fields. For example, one of the promising applications is magnetic hyperthermia in the medical field. When a temperature difference is locally generated by a small heated sphere in liqu...

There have recently been a number of works on magnetic hyperthermia, which is a medical treatment for killing cancer cells by raising their temperatures. A promising heating method is electromagnetic induction of magnetic particles delivered or injected into cancer cells. For accomplishing this treatment, it is crucial to precisely measure and cont...

When a temperature difference is locally generated by a small heated sphere in liquid, natural convection occurs, and largely affects the temperature and velocity fields. However, a transient temperature field during natural convection in such a small region has never been directly measured. In this study, using the temperature imaging method based...

Natural convection occurring from a very small heat source affects temperature, flow, and concentration fields in liquid. Therefore, for the purpose of experimentally elucidating the natural convection, we have measured the transient temperature distributions in water and investigated the heat transfer using the near-infrared (NIR) imaging method....

Magnetic hyperthermia, which is a cancer treatment technique using ferromagnetic nanoparticles such as iron oxide ones heated by electromagnetic induction, has been intensively studied because the nanoparticles can be aggregated or adsorbed selectively on cancer cells. In these studies, the temperatures of liquid containing a large number of nanopa...

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This technique utilizes wavelengths of 1150 and 1412 nm, at which the absorption coefficient of water is dependent on temperature. Water or a non-turbid aqueous gel containing a 2.0-mm- or 0.5-mm-diameter...

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...

This paper presents a method of measuring the temperature of water near a 1-mm-diameter magnetic sphere under induction heating. The method is based on the temperature dependence of the absorption coefficient of water at a wavelength of 1150 nm. In this study, two-dimensional images of the absorbance, which is the transverse projection of the absor...

This study focuses on the decomposition reaction characteristics of micro-glow corona with solid materials. Micro-glow corona is a very small plasma, which is able to be generated on the tip of a needle electrode at atmospheric pressure. In this study, a hollow electrode with an inner dimeter of 4 mm was used as a counter electrode to generate the...

This paper is devoted to the measurement and analysis of temperature distributions around gel droplets containing micromagnetic particles heated inductively. For the measurement, a near-infrared temperature imaging technique based on the temperature dependence of the absorption coefficient of water at a wavelength of 1412 nm was used. By applying t...

This study investigated the interaction between micro-glow corona and organic materials. Micro-glow corona is very small plasma, which is generated on the tip of a needle electrode at atmospheric pressure. In this study, a hollow electrode with an inner dimeter of 4 mm was used as a counter electrode to generate the micro-glow corona. In addition,...

This paper proposes a novel imaging method using near infrared light of single wavelength to visualize the concentration distribution of salt generated by neutralization reaction of aqueous solutions of acid and alkali in a microfluidic channel. This method is based on the absorption characteristics of the aqueous solutions at the wavelength of 152...

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 d...

Temperature dependence of diffusion coefficient of ethanol in dilute ethanol aqueous solutions is investigated by using a simultaneous imaging method of temperature and concentration. The simultaneous imaging is achieved by absorption imaging with two wavelengths of 1905 nm and 1935 nm in the ν_2+ν_3 absorption band of water. The absorbance at 1905...

This paper shows heat generation rates of a 1-mm-diameter magnetic sphere at different positions in a magnetic field. To determine the heat generation rates, temperature distributions of water around the sphere were measured by the near-infrared absorbance imaging method based on the temperature dependence of absorbance of water at the wavelength o...

It is important and required for chemical analysis/synthesis using microfluidic channels to visualize diffusion phenomena and chemical reactions. We have thus developed a near-infrared (NIR) absorption imaging method to simultaneously measure the temperature and concentration distributions of aqueous solutions. This method is based on the fact that...

This paper focuses on the mixing phenomena at the neutralization reaction interface in a microchannel. Visualization of diffusion and chemical reaction of the aqueous solutions of hydrochloric acid and sodium hydroxide in microchannel is performed by using a novel imaging technique based on the near-infrared absorption spectroscopy of aqueous solut...

This paper presents a simultaneous imaging method of the temperature and concentration of ethanol aqueous solutions in a microchannel. Absorbance images at the two wavelengths in the ν_2 + ν_3 absorption band of water: 1905 nm and 1935 nm, are simultaneously acquired and converted to the temperature and concentration images. The absorbance at 1905...

Free convection generated in the fluid temperature difference by local heating, influences that can`t be ignored in heat transfer characteristics. Therefore, it is required to measure the amount of heat generated up to the free convection occurs. In previous studies, we've been estimated for the temperature distribution and the free convection arou...

We propose a novel method for estimating three-dimensional temperature distributions of water in a free convection field around a small heated sphere. This method consists of a near-infrared absorption imaging with a wavelength of 1150 nm and inverse Abel transform. Since temperature distributions formed by free convection above a heated sphere can...

This paper describes an emission spectroscopic method using micro-glow corona to analyze minute volume gases. Glow corona is stable and very small plasma generated at an apex of needle electrode at atmospheric pressure; however, it has never been applied to material decomposition and analysis. To investigate the discharge and spectroscopic characte...

This paper introduces a novel method for imaging the temperature fields in water with a small heated sphere. This method is based on the temperature dependence of the absorption coefficient of water at the wavelength of 1150 nm. When a 1 mm diameter steel sphere in water contained in a rectangular glass cell with a light path length of 10 mm was he...

This paper describes the onset of free convection around a 1 mm diameter steel sphere heated inductively in water using a light absorption imaging method with a wavelength of 1150 nm. Since the concentric absorbance distributions formed by pure thermal conduction are distorted by free convection, the onsets of free convection are determined by meas...

This paper presents a novel method for reconstructing the temperature distributions of water around a small heated sphere and predicting the heat generation rates of the sphere. This method is based on the temperature dependence of the absorbance of water at the wavelength of 1150 nm. Absorbance images at 1150 nm were obtained when a 1 mm diameter...

This paper presents the visualization of neutralization reactions of an acid (HCl) and a base (NaOH) in a microchannel. Increases in temperature and concentration of the products, caused by the neutralization reactions, are visualized by using the absorbance images at two wavelengths in a near-infrared region: 1412 nm and 1442 nm. Absorbance images...