Permittivity Of Solutions Research Articles

High density nanofluidic channels by self-sealing for metallic nanoparticles detection

High density nanofluidic channels were successfully fabricated by a novel process, nicknamed as self-sealing process, for the detection of metal nanoparticles dispersed in water using color changes excited by polarized electromagnetic waves. The permittivities of aqueous solutions with various concentrations of metal nanoparticles were calculated by a corrected plasma model. Systematic simulations using finite difference time domain method were carried out in investigating the detection capabilities of the nanofluidic channels for silver, beryllium and copper nanoparticles in water. The pronounced color shifts indicates that the channels possess high sensitivity in the metal nanoparticles detection. The designed nanofluidic channels were then fabricated by a direct flood deposition of a silica film on a pre-replicated hydrogen silsesquioxan (HSQ) grating using electron beam lithography (EBL). The self-sealing technique possesses advantages in simplified processing, encapsulation free and potential of multi-layer nanochannels.

Evaluation of a prototype variable frequency mode soil moisture and EC probe for its final development

AbstractA prototype dielectric probe developed by the Daiki Rika Kogyo Co., Ltd, Japan, was evaluated by controlled laboratory experiments. The probe simultaneously measures the real and imaginary parts of the dielectric permittivity, which are comparable to the measurements obtained with a vector network analyser (VNA) at frequencies ranging from 10 to 160 MHz. The probe accurately (±2% error) measures the real parts of the dielectric permittivity of oil–ethanol and ethanol–water mixtures over a wide range of real permittivities (3.26 ~ 79) at frequencies ranging from 70 to 90 MHz. The imaginary parts of the dielectric permittivity of aqueous solutions are related to the electrical conductivity (EC) through a unique rational model (±2.5% error) over 80–90 MHz. Dielectric measurements by probes at the desired frequencies can eliminate/reduce the limitations of fixed‐frequency measurements, such as the effects of EC, clay composition, porosity, and organic matter, of currently available probes.

Ac/dc conductivity and ML-based evaluation of electric characteristics of methylene blue solution

Utilizing a precision LCR meter, the complex permittivity ε*(f) of methylene blue (MB) solutions in distilled water (DW) was determined at various temperatures and concentrations in the lower frequency range from 20 Hz to 2 MHz. The complex ac conductivity σ*(f) of the liquid samples was calculated using ε*(f). DC conductivity, σdc of the samples was also calculated. The effect of changes in temperature and concentration on the σ*(f) and ε*(f) of solutions are examined. A solution of MB in DW, ranging from diluted to concentrated, greatly enhances the electrical conductivity σdc. The empirical Casteel-Amis (CA) formula was employed to fit the experimental σdc values at different concentrations. Accurate measurement of complex permittivity of liquid solutions over wide range of concentration at broad range of frequencies and temperature is laborious and uneconomical. Therefore, we performed the complex permittivity measurement of the aqueous solution of MB over a limited concentration and temperature range over 201 frequency point. Then we used this experimental data in CatBoost regression model to predict the dielectric properties at intermediate frequencies and various concentrations. This model was employed to assess the performance of material characteristics using R-squared score. The study demonstrated that the CatBoost regression model can predict material performance at intermediate frequencies and concentrations while decreasing measurement resource needs by 60 %.

Dielectric Characterization of Solutions of Galactomannan Extracted from Adenanthera pavonina L.: Effects of Purification and Ethanol Concentration.

Galactomannans are polysaccharides obtained from legume seed extraction. They present a chemical structure consisting of D-mannose chains linked by glycosidic bonds and galactose branches. The main focus lies in their use as thickeners in the food industry, aimed at improving the dielectric properties of food during heating processes within the radiofrequency and microwave ranges. In this work, the prepared galactomannan samples were electrically analyzed through impedance spectroscopy, which is a powerful physical technique. From the experimental measurements, the dielectric permittivity and loss tangent of the galactomannan solutions were analyzed and the electrical modulus formalism was used to study the dielectric relaxations. Crude galactomannans exhibited higher values of permittivity, conductivity, and losses compared to purified galactomannans. Increasing ethanol concentration in galactomannan purification causes an increase in the permittivity and conductivity of galactomannan solutions. In a 1% solution, at 1 kHz, the permittivity increased from 378.56 to 538.09, while in the 2% solution, this increase was from 656.22 to 1103.24. Regarding the conductivity, at the same frequency, the increase was from 1.6 × 10-3 to 3.3 × 10-3 Ω-1m-1 and from 2.9 × 10-3 to 5.5 × 10-3 Ω-1m-1, respectively. The rise of the ethanol concentration in galactomannan purification led to a decrease in the relaxation time, from 448.56 to 159.15 μs and from 224.81 to 89.50 μs in the solution with 1 and 2%, respectively. The results suggest that galactomannan from Adenanthera pavonina L. has potential for use in the food industry.

A Novel Microwave Sensor Based on Modified Rat-Race Coupler for Extracting Real Permittivity and Concentration of Binary Aqueous Solution

A Novel Microwave Sensor Based on Modified Rat-Race Coupler for Extracting Real Permittivity and Concentration of Binary Aqueous Solution

Ion-Solvent Interactions under Confinement Hold the Key to Tuning the DNA Translocation Speeds in Polyelectrolyte-Functionalized Nanopores.

DNA sequencing and sensing using nanopore technology delves critically into the alterations in the measurable electrical signal as single-stranded DNA is drawn through a tiny passage. To make such precise measurements, however, slowing down the DNA in the tightly confined passage is a key requirement, which may be achieved by grafting the nanopore walls with a polyelectrolyte layer (PEL). This soft functional layer at the wall, under an off-design condition, however, may block the DNA passage completely, leading to the complete loss of output signal from the nanobio sensor. Whereas theoretical postulates have previously been put forward to explain the essential physics of DNA translocation in nanopores, these have turned out to be somewhat inadequate when confronted with the experimental findings on functionalized nanopores, including the prediction of the events of complete signal losses. Circumventing these constraints, herein we bring out a possible decisive role of the interplay between the inevitable variabilities in the ionic distribution along the nanopore axis due to its finite length as opposed to its idealized "infinite" limit as well as the differential permittivity of PEL and bulk solution that cannot be captured by the commonly used one-dimensional variant of the electrical double layer theory. Our analysis, for the first time, captures variations in the ionic concentration distribution across multidimensional physical space and delineates its impact on the DNA translocation characteristics that have hitherto remained unaddressed. Our results reveal possible complete blockages of DNA translocation as influenced by less-than-threshold permittivity values or greater-than-threshold grafting densities of the PEL. In addition, electrohydrodynamic blocking is witnessed due to the ion-selective nature of the nanopore at low ionic concentrations. Hence, our study establishes a functionally active regime over which the PEL layer in a finite-length nanopore facilitates controllable DNA translocation, enabling successful sequencing and sensing through the explicit modulation of translocation speed.

Polarity of Aqueous Solutions

This short review describes the expansion of the solvatochromic approach utilizing water-soluble solvatochromic dyes to the analysis of solvent features of aqueous media in solutions of various compounds. These solvent features (polarity/dipolarity, hydrogen bond donor ability (HBD acidity), and hydrogen bond acceptor ability (HBA basicity)) vary depending on the nature and concentration of a solute. Furthermore, the solvent features of water (the solvent dipolarity/polarizability and hydrogen bond donor ability) in solutions of various compounds describe multiple physicochemical properties of these solutions (such as the solubility of various compounds in aqueous solutions, salting-out and salting-in constants for polar organic compounds in the presence of different inorganic salts, as well as water activity, osmotic coefficients, surface tension, viscosity, and the relative permittivity of aqueous solutions of different individual compounds) and are likely related to changes in the arrangement of hydrogen bonds of water in these solutions.

Microwave Frequency Dependent Dielectric Properties of Blood as a Potential Technique to Measure Hydration

Tissue dehydration is known to have adverse effects on health and is highly challenging to characterize in vitro due to the complexity of the cell/tissue organisation. There have been a large number of studies reporting the dielectric properties of animal and human tissue explants or bodily fluids such as urine or blood over a wide frequency range from 10 Hz to 100 GHz. However, variations in blood composition involving the cell type, haematocrit (HCT) protein levels, ionic conductivity, electrolyte or glucose concentration will affect the dielectric measurements. The present study examined the effects of physiological osmotic solutions with NaCl (280 mOsmol/kg to 300 mOsmol/kg), HCT (35% to 50%) and albumin (3.5 g/dl to 5.5 g/dl) isolated from bovine blood on the dielectric properties measured at frequencies spanning from 0.5 GHz to 20 GHz using an open-ended co-axial probe. Measurements demonstrated linear correlations between permittivity and loss factor of blood solutions with varying HCT levels, albumin or osmolality such that a high protein concentration reduced the dielectric response in a dose-dependent manner. Whilst the spectral trends for the permittivity response to HCT and albumin were similar in a concentration-dependent manner, the loss factor profile was influenced by osmolality of the solution. In summary, we characterized the dependence of the microwave dielectric properties of blood on HCT, albumin and osmolality. The dielectric measurement technique has the potential to determine hydration levels for future diagnostic and therapeutic devices.

Modeling of dilution enthalpies within implicit-solvent models for electrolytes

This work deals with the calculation of dilution enthalpies for strong aqueous electrolyte solutions when their thermodynamic properties are described within implicit-solvent models. The solution is modeled as a collection of charged hard spheres in a continuum solvent. A new general expression is obtained that accounts for the variation of the solution permittivity, of the size of the ions, and of the specific volume of the solution, with temperature and concentration. This expression is used to compute the enthalpies of LiCl aqueous solutions at temperatures in the range of 25∘C to 100∘C for concentrations up to 6 mol kg−1. The mean spherical approximation (MSA) model with implicit continuum solvent is employed to describe the thermodynamic properties of these solutions.

The effect of temperature on permittivity measurements of aqueous solutions of glucose for the development of non-invasive glucose sensors based on electromagnetic waves

This article presents for the first time an empirical study that shows the importance of considering temperature when analyzing the permittivity (dielectric constant) of aqueous glucose solutions of various concentrations. The permittivity is a parameter that is investigated by researchers as a biomarker for non-invasive measurement of glucose without drawing blood. The development of this technology will allow personalized healthcare diagnostics to monitor and prevent diabetes. Since human glucose levels in the blood vary in the range of a few milligrams per decilitre, estimating such small variations of glucose will require a highly accurate and repeatable sensing technology. Electromagnetic (EM) waves, specifically in the microwave and terahertz frequency ranges, have shown promise in detecting changes in the electrical properties of blood plasma as they relate to glucose concentration. However, it's important to note that while this technology shows promise, it is still in the research and development phase. It is shown here that the body temperature can affect the accuracy of the blood glucose measurements. Experiments were conducted with different glucose concentration solutions under various temperatures and the complex permittivity of the glucose was studied across a wide frequency range from 400 MHz to 11 GHz. The rise in thermal energy normally causes dipolar liquids like water to vibrate and rotate disrupting the alignment of the dipoles in response to an electric field thereby reducing its permittivity. Empirical results however show that for aqueous solution of glucose the permittivity increases with rise in temperature from 16 °C to 37 °C. This is attributed to the polar nature of the water and glucose molecules that becomes more pronounced with increased thermal energy. Based on the experimental results an accurate analytical expression is derived that considers the temperature of the aqueous glucose solution. The accuracy of the analytical expression is shown experimentally to be above 99%. The findings from the study should enable the design of accurate non-invasive glucose monitoring devices based on electromagnetic sensing techniques.

Design of a Microwave Heating and Permittivity Measurement System Based on Oblique Aperture Ridge Waveguide.

In this paper, an oblique aperture ridge waveguide operating at 2450 MHz is proposed, and, using the ridge waveguide, a permittivity measurement system is constructed which can measure the permittivity of materials during microwave heating. The system calculates the amplitudes of the scattering parameters by using the forward, reflected and transmitted powers of the power meters, and it reconstructs the permittivity of the material by combining the scattering parameters with an artificial neural network. The system is used to measure the complex permittivity of mixed solutions of methanol and ethanol with different ratios at room temperature, and the permittivity of methanol and ethanol with increasing temperature, from room temperature to 50 °C. The measured results are in good agreement with the reference data. The system allows simultaneous measurement of the permittivity with microwave heating and provides real-time, rapid changes in the permittivity during heating, avoiding thermal runaway and providing a reference for applications of microwave energy in the chemical industry.

ОПРЕДЕЛЕНИЕ ПЛОТНОСТИ И ДИЭЛЕКТРИЧЕСКОЙ ПРОНИЦАЕМОСТИ РАСТВОРОВ РЕДКОЗЕМЕЛЬНЫХ ЭЛЕМЕНТОВ СРЕДНЕТЯЖЕЛОЙ ГРУППЫ В ВОДНЫХ РАСТВОРАХ И В ЭКСТРАКТАХ КИСЛЫХ ФОСФОРОРГАНИЧЕСКИХ ЭКСТРАГЕНТОВ

Co-extraction of rare-earth elements from chloride solutions containing total rare-earth elements by a mixture of extractants mono-2-ethylhexyl ester of 2-ethylhexylphosphonic acid (P507) + di(2,2,4-trimethylpentyl)phosphinic acid (Cyanex 272) + 10 about. % TBP in isopar-l with a mass concentration of P507 + Cyanex 272 - 15%. The density and permittivity of solutions of rare-earth elements of the medium-heavy group in aqueous solutions and in extracts of acidic organophosphorus extractants have been determined. Initial concentrations in REE GH solutions ranged from 0.15 to 1.7 mol/dm3. The features of complex formation in a mixture of praseodymium metal and P507 extractant were studied. The initial concentrations in praseodymium solutions ranged from 0.014 to 0.149 mol/dm3.

Measurement of low‐loss aqueous solutions permittivity with high detection accuracy by a contact and free‐label resonance microwave sensor

SummaryIn this paper, a microwave sensor is designed and built to measure the permittivity of aqueous solutions. The samples used in this experiment are different purities of ethanol mixed with water. Ethanol solution with different purities is a widely used material in industry. Structures of meander, ladder, and T‐structure were used to design the sensor. Then the designed sensor is simulated in CST software in range of relative dielectric from 10 to 80. After obtaining the desired answer in the simulation, the proposed sensor is built on the Rogers 4003 substrate, the built‐in sensor measured ethanol solution with a purity of 5% to 35% (equivalent to permittivity of 76 to 58), and is showed a sensitivity of 4% and a Q‐factor of 3500. The results of simulation and measurement are consistent with each other, and they indicated that the proposed sensor beyond the fluids can be supported and determine their relative dielectrics.

3D Printed Platform for Impedimetric Sensing of Liquids and Microfluidic Channels.

Fused deposition modeling 3D printing (FDM-3DP) employing electrically conductive filaments has recently been recognized as an exceptionally attractive tool for the manufacture of sensing devices. However, capabilities of 3DP electrodes to measure electric properties of materials have not yet been explored. To bridge this gap, we employ bimaterial FDM-3DP combining electrically conductive and insulating filaments to build an integrated platform for sensing conductivity and permittivity of liquids by impedance measurements. The functionality of the device is demonstrated by measuring conductivity of aqueous potassium chloride solution and bottled water samples and permittivity of water, ethanol, and their mixtures. We further implement an original idea of applying impedance measurements to investigate dimensions of 3DP channels as base structures of microfluidic devices, complemented by their optical microscopic analysis. We demonstrate that FDM-3DP allows the manufacture of microchannels of width down to 80 μm.

Investigation Into Variation of Resistivity and Permittivity of Aqueous Solutions and Soils With Frequency and Current Density

Soil parameter characterization and the variation of permittivity and resistivity with frequency (dispersion) and current density have been the subject of many experimental studies but significant differences in measured values are found in the literature due to different testing approaches, apparatus, and test sample composition. This article first presents a comprehensive review of this previous body of work. Then, new experiments on soils and electrolytes with test frequencies in the range 1 Hz to 10 MHz and with current densities from 1 to 35 mA/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> are described. Such results help clarify the effects of frequency, soil moisture, electrolyte concentration, and electrode material on the measured test medium parameters. The contribution of the electrode-electrolyte interface (EEI) and the influence of current density are particularly highlighted. These findings indicate that some previous measurements may have overestimated the measured values of resistivity and permittivity due to the EEI effect. Finally, the test results are compared with soil parameter equations from CIGRE TB781.

The simulation of a green room-temperature ternary solution of water, methanol and 1-ethyl-3-methyl imidazolium chloride by all-atom Monte Carlo and DFT computational approaches

A highly dense ternary solution of water, methanol and 1-ethyl-3-methyl imidazolium chloride [emim][Cl] was investigated by a Monte Carlo (MC) program written in C language, Density Functional Theory (DFT) and Atoms-In-Molecules (AIM) theory. The all-atom approach in MC calculations of a ternary solution, the use of nonzero LJ parameters for all hydrogen atoms in simulation box and the creation of a new strategy for filling simulation box with many molecules were adopted in this research to yield a comprehensive, accurate and different work. The radial distribution function, the molar heat capacities in constant volume and pressure, the thermal expansivity, and the isothermal compressibility of the ternary system were calculated. The chemical potentials were calculated at different temperatures through Widom insertion method and the behaviors of both ideal and excess parts of chemical potentials were analyzed versus temperature. The value of electric permittivity of solution, the change of number of methanol and water molecules and the replacement of chloride anion with iodide in ionic liquid were also explored through separate simulations. The solvation structure and coordination number were investigated for various systems. The optimized sites for water and methanol around [emim]+ recognized by DFT and the HOMO and LUMO isosurfaces were discussed. Also, the hydrogen bonds between components of ternary solution were determined by AIM theory. It was shown that the results of quantum mechanics calculations confirm those of MC simulations.

ПЛОТНОСТЬ И ДИЭЛЕКТРИЧЕСКАЯ ПРОНИЦАЕМОСТЬ ВОДНЫХ РАСТВОРОВ ХЛОРИДОВ РЗЭ СРЕДНЕ-ТЯЖЕЛОЙ ГРУППЫ В ПРИСУТСТВИИ ХЛОРИДА НАТРИЯ

The densities of mixed solutions of rare-earth elements of the medium-heavy group with NaCl were determined by the pycnometric method. Aqueous solutions of NaCl with concentrations of 10,50,100,150,200, 220 g/dm3 containing lanthanide chlorides of the medium-heavy group with a concentration range from 0.05 mol/dm3 to 1.73 mol/dm3 at pH = 1.5 were studied. Dielectric permittivity of solutions with the concentration of the aggregate REE in the aqueous phase from 0.05 mol/dm3 to 0.75 mol/dm3 and NaCl concentration equal to 150 g/dm3 was measured in the frequency range from 0.5 to 110 MHz. Empirical equations were constructed that relate the density of the solution to the concentration of NaCl, to the concentration of the sum of rare-earth elements, and to the dielectric permittivity. These equations make it possible to calculate the concentration of sodium chloride from the density of solution and from the aggregate REE concentration. The empirical formula makes it possible to calculate the concentration of the sum of REE chlorides of the medium-heavy group at a known concentration of sodium chloride from the dielectric permittivity of the aqueous solution

Relationships between Molecular Structure of Carbohydrates and Their Dynamic Hydration Shells Revealed by Terahertz Time-Domain Spectroscopy.

Despite more than a century of research on the hydration of biomolecules, the hydration of carbohydrates is insufficiently studied. An approach to studying dynamic hydration shells of carbohydrates in aqueous solutions based on terahertz time-domain spectroscopy assay is developed in the current work. Monosaccharides (glucose, galactose, galacturonic acid) and polysaccharides (dextran, amylopectin, polygalacturonic acid) solutions were studied. The contribution of the dissolved carbohydrates was subtracted from the measured dielectric permittivities of aqueous solutions based on the corresponding effective medium models. The obtained dielectric permittivities of the water phase were used to calculate the parameters describing intermolecular relaxation and oscillatory processes in water. It is established that all of the analyzed carbohydrates lead to the increase of the binding degree of water. Hydration shells of monosaccharides are characterized by elevated numbers of hydrogen bonds and their mean energies compared to undisturbed water, as well as by elevated numbers and the lifetime of free water molecules. The axial orientation of the OH(4) group of sugar facilitates a wider distribution of hydrogen bond energies in hydration shells compared to equatorial orientation. The presence of the carboxylic group affects water structure significantly. The hydration of polysaccharides is less apparent than that of monosaccharides, and it depends on the type of glycosidic bonds.

Anomalous dielectric behaviors of electrolyte solutions confined in graphene oxide nanochannels

Dielectric behavior of salt aqueous solutions with various concentration in pristine and oxide graphene nanochannels has been investigated by means of molecular dynamic simulations. The motivation in performing this integrated set of simulations was to provide deep insight into the interaction between the size of the enclosure and the oxidation degree of the membrane sheets on the dielectric properties. It was shown that the dielectric permittivity of both aqueous and NaCl solution in confined phase exhibits an anisotropic behavior. The in-plane component decreases with the increase of the concentration of NaCl solution while an increase of the out-of-plane dielectric is observed and these out-of-plane components exhibit a non-monotonous trend and thus exist a critical concentration of NaCl solution with 0.2 mol/L and 0.4 mol/L for both pristine and oxide graphene nanochannels, respectively. This peculiar dielectric behavior results from the addition of ions that significantly perturb the hydrogen bonding network of the confined system, and hence leading to a fluctuation of dipolar of water molecules and dielectric permittivity.

Corrections to “Complex Permittivity of NaOH Solutions Used in Liquid-Metal Circuits”

In the above article [1] , Table 1 , Figs. 4 and 5, and Appendices A and B of the associated supplementary materials unfortunately contain minor errors. This article serves to correct those errors.