Change In Permittivity Research Articles

Energy Tunneling Behavior in Geometrically Separated Wave Guides

In this paper, characteristics of energy tunneling channel between the waveguides geometrically separated by a coaxial cable are studied. The novel aspect of design is use of coaxial channel to connect the waveguides while maintaining the energy tunneling phenomena. As anticipated the tunneling frequency depends upon the length of wire inside the waveguide and the length of the coaxial cable. The tunneling frequency also depends upon the dielectric constant of the material inside the waveguide and coaxial cable. At tunneling frequency the field strength (E and H) in the channel is extremely high, making the channel extremely sensitive to small change in permittivity of dielectric occupying the channel. The advantage of the proposed design is, its ability to tune to desired tunneling frequency just by changing the length of the coaxial cable without the need to redesign the waveguide height to accommodate the long tunneling wires. This structure can be used as dielectric sensor both for solid or liquid dielectrics just by placing the sample in coaxial cable cavity, contrary to previously report work where the sample has to be placed inside the waveguide.

Change in the Magnetocapacity in the Paramagnetic Region in a Cation-Substituted Manganese Selenide

The capacity and the dielectric loss tangent of a Gd x Mn1–xSe (x ≤ 0.2) solid solution have been measured in the frequency range 1–300 kHz without a magnetic field and in a magnetic field of 8 kOe in the temperature range 100–450 K, and the magnetic moment of the solid solution has been measured in a field of 8.6 kOe. The magnetocapacity effect and the change in the magnetocapacity sign have been observed in room temperature in the paramagnetic region. A correlation of the changes in the dielectric permittivity and the magnetic susceptibility with temperature has been revealed. The magnetocapacity is described using the model with orbital electron ordering and the Maxwell–Wagner model.

DIELECTRIC SENSITIZATION OF ZEOLITIC IMIDAZOLATE FRAMEWORK-8 (ZIF-8) NANOPOWDER

Metallo-organic complexes are a class of materials that are increasingly used in sensory applications. Zeolitic imidazolate frameworks (ZIFs) are their subclass that are topologically isomorphic with zeolites. The porosity of the crystals and their chemical structure, as well as their thermal and chemical stability, make some of these materials (ZIFs) very suitable for making sensors. The large specific area of micro and nano particles is an important parameter for sensor applications. Despite the fact that the dielectric characterization of powders in the RF domain was neglected in scientific works, this method can have great practical importance. This paper presents the results of the dielectric characterization of the ZIF-8 nanopowder in the frequency range of 24 Hz to 24 KHz. The results indicate that the presence of evaporation of water, ethanol and methanol leads to major changes in the dielectric permittivity of ZIF-8 nanopowder.

Characterization of an Interdigitated Capacitive Structure With Branches for Relative Humidity Sensing

An interdigitated capacitive structure whose fingers have branches across them is described in this article. By changing the traditional interdigitated electrodes (IDE), the area where the sensor is defined can be reduced by a third, while its capacitance and sensitivity are maintained. This enhancement with respect to the traditional one is obtained thanks to the contribution to the capacitance not only in the finger length direction (unidimensional) but also in the finger width dimension (2-D). In order to test the sensitivity enhancement of this device in comparison with the conventional IDE, two version of this structure and the classical IDE have been manufactured by inkjet printing on flexible foil and characterized as relative humidity (RH) sensor. For this purpose, a substrate whose electrical permittivity changes with moisture content has been selected. Their capacitances have been measured as a function of RH in a wide range of frequencies at different temperatures, obtaining comparable results as a function of the RH and temperature. However, in the case of the sensor with closer branches, the response changes above 50%RH, showing a significantly higher sensitivity due to the fact that electrodes are much closer than in the other structures. The accumulation of water molecules between consecutive fingers occurs at lower values of moisture content than in the other layouts, resulting in higher capacitance values due to the higher electrical permittivity of water.

Effect of Cyanide on Mitochondrial Membrane Depolarization Induced by Uncouplers.

In this work, it was found that the ability of common uncouplers - carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and 2,4-dinitrophenol (DNP) - to reduce membrane potential of isolated rat liver mitochondria was diminished in the presence of millimolar concentrations of the known cytochrome c oxidase inhibitor - cyanide. In the experiments, mitochondria were energized by addition of ATP in the presence of rotenone, inhibiting oxidation of endogenous substrates via respiratory complex I. Cyanide also reduced the uncoupling effect of FCCP and DNP on mitochondria energized by succinate in the presence of ferricyanide. Importantly, cyanide did not alter the protonophoric activity of FCCP and DNP in artificial bilayer lipid membranes. The causes of the effect of cyanide on the efficiency of protonophoric uncouplers in mitochondria are considered in the framework of the suggestion that conformational changes of membrane proteins could affect the state of lipids in their vicinity. In particular, changes in local microviscosity and vacuum permittivity could change the efficiency of protonophore-mediated translocation.

Fabrications of Nanocomposite Gold-Polymer Metamaterials Consisting of Periodic Microcavities with Tunable Optical Properties

Nanocomposite gold-polymer metamaterials (MMs) were developed in a series of steps. The colloidal gold nanoparticles (Au NPs) were prepared using seeding growth technique. The NPs were then electro-deposited into the micro-pattern structure of polymer thin film formed on the surface of indium tin oxide substrates (ITO). This micro-pattern structure made of positive photoresist (PR) polymer were present in the well-ordered square microcavities in the size range of 52–65μm (length), 1.3–1.6μm (depth) and 17–29μm (interspace length). Field emission scanning electron microscopy (FESEM), scanning transmission electron microscopy (STEM) and atomic-force microscopy (AFM) images confirmed the presence of Au NPs within the microcavities. This nanocomposite was named as patterned Au-PR/ITO and was compared with random-patterned Au-PR/ITO and the bare PR/ITO. The change of refractive index and complex permittivity in the UV–vis range revealed that the periodic arrangements of microcavities containing the Au NPs could result in new exploration in the optical and electromagnetic properties.

ClotChip: A Microfluidic Dielectric Sensor for Point-of-Care Assessment of Hemostasis.

This paper describes the design, fabrication, and testing of a microfluidic sensor for dielectric spectroscopy of human whole blood during coagulation. The sensor, termed ClotChip, employs a three-dimensional, parallel-plate, capacitive sensing structure with a floating electrode integrated into a microfluidic channel. Interfaced with an impedance analyzer, the ClotChip measures the complex relative dielectric permittivity, ϵr , of human whole blood in the frequency range of 40Hz to 100MHz. The temporal variation in the real part of the blood dielectric permittivity at 1MHz features a time to reach a permittivity peak, , as well as a maximum change in permittivity after the peak, , as two distinct parameters of ClotChip readout. The ClotChip performance was benchmarked against rotational thromboelastometry (ROTEM) to evaluate the clinical utility of its readout parameters in capturing the clotting dynamics arising from coagulation factors and platelet activity. exhibited a very strong positive correlation ( r = 0.99, p < 0.0001) with the ROTEM clotting time parameter, whereas exhibited a strong positive correlation (r = 0.85,p < 0.001) with the ROTEM maximum clot firmness parameter. This paper demonstrates the ClotChip potential as a point-of-care platform to assess the complete hemostatic process using <10μL of human whole blood.

Study of dielectric properties of leukocytes for the determination of malignancy by capacitive type MEMS sensor

The present work deals with a non-clinical scheme to develop a system-on-chip for the detection and identification of the malignant cells in a known volume of white blood cells (WBC) using MEMS capacitive sensor. In presence of cancerous cells, the sensor produces a change in the value of capacitance which reflects a significant variation of dielectric permittivity. For this purpose, a double shell electrical model of WBC is designed and analyzed in frequency range 20 kHz–10 MHz due to the polarization of cell membrane. The polarization is induced using electroporation process where the plasma membrane of the blood cell is polarized to a membrane potential of about 0.5–1 V with a supply of 1 V which makes cell membrane semi permeable for the exchange of ions, thus producing change in dielectric permittivity. In order to determine the change in dielectric permittivity, an electrostatic MEMS capacitive sensor is virtually fabricated with a pair of rectangular electrodes in which the second electrode is further divided into four sub-plates in same plane. This change in permittivity results in change of output capacitance, finally differentiate a malignant cell from a normal one.

Terahertz Plasmonic Switch Based on Periodic Array of Graphene/Silicon

We present a plasmonic switch based on anisotropic structure consisting of graphene and silicon layers, like one-dimensional photonic crystal. The plasmonic wave in this switch is propagated inside the MgF2 core surrounded by two periodic arrays of graphene / silicon. Changing the chemical potential of graphene leading to the change of permittivity of anisotropic array, we can adjust the propagation length of plasmonic wave. The obtained results show that, at the frequency of 30 THz with adjusting the chemical potential of graphene, the chemical potential of 0.4 eV and 0.2 eV can be obtained for the ON_state and OFF state, respectively. Also, the ON/OFF ratio is about 24.

Field-Deployable Wireless Sensor Networks for Mapping Inorganic N-Containing Species in Soil

Conventional practice of applying fertilizer and irrigation are empirical, often resulting in negative consequences to the environment and human welfare due to the insufficient or excess usage of fertilizer and water. Hence there is a persistent need for the knowledge to assist farmers in determining the quantity and timing of fertilizer and water application to maximize crop yield, minimize waste, and reduce cost. In this study, we aim to develop a highly sensitive radio frequency microfluidic coplanar waveguide array (MCWA) based sensor that can measure N-containing species down to the 3 picomolar by detecting small changes in permittivity of the sample solution upon analyte binding. Based on the single senor unit, we will develop an integrated MCWA sensor array by constructing a series of electrical and microfluidic circuits with each of the sensor units targeting specific analyte species for simultaneous measurement of different N-containing species simultaneously. The MCWA sensor array will be further integrated into a field-deployable soil probe and used to demonstrate the ability of mapping nitrate, ammonium, pH and soil moisture content on the farm using a network of sensor probes spread over a large area. The data from the sensor networks can be used to determine when and how much fertilizer and water should be applied, enabling just-in-time and just-enough geospatial applications of fertilizer and irrigation water, which would contribute to the food-energy-water nexus by increasing crop yield and, at the same time, reducing usage of water and fertilizer.

Investigation of tunable omnidirectional band gap in 1D magnetized full plasma photonic crystals

In this work, the creation of the omnidirectional band gap (OBG) in a tunable full plasma photonic crystal has been investigated theoretically. The full plasma photonic crystal is made of the bulk cold plasma which is embedded in the DC periodic magnetic field. The influence of the periodic external magnetic field leads to periodic changes of plasma permittivity and creation of unit cells. The formation of OBGs is limited by the Brewster's angle; here we have omitted this limitation by applying certain condition for permittivity layers of the unit cell. The results are investigated by means of the transfer matrix method. The numerical results show that the band width of OBG can be enlarged by increasing the thickness of the unit cell and density of plasma. Also it can be decreased by increasing the magnetic field strength.

External electric field effects on Schottky barrier at Gd3N@C80/Au interface

The effects of the external electric field on the height of the Schottky barrier at the Gd3N@C80/Au interface were studied by measuring current-voltage characteristics at various temperatures from 200 K to 450 K. The Gd3N@C80 sample with the conduction/forbidden/valence energy band structure had a face-centered cubic crystal structure with the average grain size of several nanometers. The height of the Gd3N@C80/Au Schottky barrier was confirmed to be 400 meV at a low electric field at room temperature. Moreover, the height decreases with the increasing external electric field through a change of permittivity in the Gd3N@C80 sample due to a polarization of the [Gd3]9+−[N3−+C806−] dipoles in the Gd3N@C80 molecule. The field-dependence of the barrier height can be described using a power math function of the electric field strength. The results of the field-dependent barrier height indicate that the reduction in the Schottky barrier is due to an image force effect of the transport charge carrier at the Gd3N@C80/Au interface.

Ultrafast photoionization and excitation of surface-plasmon-polaritons on diamond surfaces

Ultrafast plasmonics of novel materials has emerged as a promising field of nanophotonics bringing new concepts for advanced optical applications. Ultrafast electronic photoexcitation of a diamond surface and subsequent surface plasmon-polaritons (SPPs) excitation are studied both theoretically and experimentally. Following photoexcitation on the rising edge of the pulse, transient surface metallization was found to occur for laser intensity near 18TW/cm2 due to enhancement of the impact ionization rate. In this regime, the dielectric constant of the photoexcited diamond becomes negative in the trailing edge of the pulse thereby increasing the efficacy with which surface roughness leads to inhomogeneous energy absorption at the SPP wave-vector. These transient SPP waves imprint permanent fine and coarse surface ripples oriented perpendicularly to the laser polarization. The theoretical modeling is supported by the experiments on the generation of laser-induced periodic surface structure on diamond surface with normally incident 515-nm, 200-fs laser pulses. Sub-wavelength (Λ≈100nm) and near wavelength (Λ≈450nm) surface ripples oriented perpendicularly to the laser polarization emerged within the ablative craters with the increased number of laser shots. The spatial periods of the surface ripples decrease moderately with the increasing exposure. The comparison between experimental data and theoretical predictions demonstrates the role of transient changes of the dielectric permittivity of diamond during the initial stage of periodic surface ripple formation upon irradiation with ultrashort laser pulses.

A Glucose Sensing System Based on Transmission Measurements at Millimetre Waves using Micro strip Patch Antennas

We present a sensing system operating at millimetre (mm) waves in transmission mode that can measure glucose level changes based on the complex permittivity changes across the signal path. The permittivity of a sample can change significantly as the concentration of one of its substances varies: for example, blood permittivity depends on the blood glucose levels. The proposed sensing system uses two facing microstrip patch antennas operating at 60 GHz, which are placed across interrogated samples. The measured transmission coefficient depends on the permittivity change along the signal path, which can be correlated to the change in concentration of a substance. Along with theoretical estimations, we experimentally demonstrate the sensing performance of the system using controlled laboratory samples, such as water-based glucose-loaded liquid samples. We also present results of successful glucose spike detection in humans during an in-vivo Intravenous Glucose Tolerance Test (IVGTT). The system could eventually be developed into a non-invasive glucose monitor for continuous monitoring of glucose levels for people living with diabetes, as it can detect as small as 1.33 mmol/l (0.025 wt%) glucose concentrations in the controlled water-based samples satisfactorily, which is well below the typical human glucose levels of 4 mmol/l.

Structure ordered Ca3TaGa3Si2O14 crystal-based liquid phase sensors with enhanced stability and sensitivity

In this study, lateral-field-excitation (LFE) bulk acoustic wave sensors based on the structure ordered Ca3TaGa3Si2O14 (CTGS) crystal are investigated. It is found that LFE devices using (yxl)-6° CTGS crystal can operate with the pseudo-LFE mode. The impedance characteristics and sensitivities of the devices are measured and compared with the LFE devices based on structure disordered langasite (LGS) crystal. The experimental results show that the CTGS LFE sensor can achieve higher Q-factors than the LGS LFE sensor, which indicates that the former has higher frequency-stability. In addition, the CTGS LFE sensor is nearly 2 times more sensitive to both liquid conductivity and permittivity changes compared to the LGS LFE sensor. For liquid acoustic viscosity changes, the CTGS LFE sensor is approximately 1.3 times more sensitive than the latter. In some chemical and biological analysis process, mechanical and electrical property changes of analytes need to be measured simultaneously, therefore the LFE sensors based on the structure ordered CTGS crystal have a good potential for use in liquid-phase sensing of chemical and biological systems.

Studying the Influence of Temperatures, Used for Processing ABS, PA 6.6 and POM, on Certain Electrical Properties, when Injection Moulding Items for the Automotive Industry, by Methods Employed for Determining Relative Permittivity and the Dielectric Dissipation Factor

This paper analyses the influence of processing temperatures of acrylonitrile butadiene styrene (ABS), polyamide 6.6 (PA 6.6) and polyoxymethylene (POM) on some electrical properties when injecting items used in the automotive industry. The ABS specimens were made at the following injection temperatures: 220, 230, 240 and 250�C. The PA 6.6 specimens were made at the following injection temperatures: 280, 290, 300, 310 and 320�C. The POM specimens were made at the following injection temperatures: 180, 190, 200, and 210�C. The determination of electrical properties were carried out using the methods for determining the relative permittivity and the dielectric dissipation factor using zero method with Schering bridge. It was found in the three polymers analysed that the temperature rise processing by injection leads to insignificant changes in relative permittivity (er) and dielectric dissipation factor (tgd).

Surface Plasmons-Polaritons, Surface Waves, and Zenneck Waves: Clarification of the terms and a description of the concepts and their evolution

The first objective of this article is to explain what surface plasmons and surface plasmon polaritons are. The term surface plasmons (SPs) was first coined in the middle of the 20th century to study the response of thin metal foils at petahertz frequencies when subjected to fast electron bombardment. SPs are coherent electron oscillations that exist at the interface between two materials where the real part of the permittivity changes sign across the interface. When an SP couples with a photon, the resulting hybrid excitation is called a surface plasmon polariton (SPP). SP refers to the charge oscillations alone, while SPP refers to the entire excitation of the charge oscillations and the electromagnetic (EM) wave. Under the right conditions, the photon can excite a longitudinal wave of electrons in the metal. The second objective is to describe the evolution of these concepts over the years and illustrate their relation to a surface wave and not to a Zenneck wave. Both Zenneck and surface waves are transverse magnetic (TM) waves. The surface waves thus cannot be excited by transverse EM (TEM) waves but rather by an electron beam that can be effectively generated by a source of electrons or a quasiparticle such as an evanescent wave, which can tunnel through the medium and thus excite the electrons. This electron wave produces its own EM wave, and this plasmonic wave is confined to a very small region near the interface. Hence, SPP is a surface wave with a longitudinal field component that propagates at the interface between a metal and a dielectric at petahertz when the conditions are right and can propagate along the metal-dielectric interface at a wavelength that is shorter than that of incident light until its energy is lost either via absorption in the conductivity of the metal or through radiation in free space. The longitudinal surface wave of an SPP is sometimes wrongly associated with a Zenneck wave. Zenneck wave is produced at the zero of the reflection coefficient of a plane incident TM wave (at the Brewster angle of incidence) on an air-dielectric interface, whereas surface waves are produced when the TM reflection coefficient is infinite. Both the Zenneck wave and the surface wave are TM waves and are nonradiating, as they have, in general, exponentially decaying fields with distance. For the Zenneck wave, the evanescent transverse field components do not change appreciably with frequency (because the phenomenon of Brewster angle is independent of frequency), whereas for a surface wave, with an increase of the frequency the wave is more closely coupled to the surface. This property makes it possible to distinguish between these two evanescent waves. SPP is generally coupled with Raman scattering and not with Rayleigh scattering. These points are illustrated in the remainder of the article. Hence, surface plasmons/polaritrons are surface waves that are the solution of Maxwell's equations unless perhaps there is a resonant Raman scattering, which is equivalent to exciting the structure with an incident frequency corresponding to the electronic absorption bands, as illustrated in A Survey of the Various Natures of Light Scattering.

Разработка сверхвысокочастотной установки контейнерного типа для термообработки крови и жиросодержащего сырья

A microwave installation was created to boil waste products of poultry and animal slaughtering in a periodic mode. It consists of a horizontal cylindrical screening body. Inside it a perforated disc-rotor from non-ferromagnetic material, rotating the motor is installed. The cylindrical resonators are rigidly fixed on the periphery of the disc-rotor. Inside each resonator the removable dielectric heat resistant containers are mounted by clamps, which covers are perforated. The inner surface of the containers is covered with a silicone material. Microwave generator units are installed on the cover of shielded enclosure, opening with handles by hinges. At the base of the body there is a drain connection. To justify structurally and technological parameters of microwave installation we analyzed the changes in the electrical parameters of the muscle tissue, skin, bone, fat, depending on the frequency of electromagnetic fields exposure. The permittivity changes of raw materials, wavelength in the feed, penetration depth of electromagnetic radiation in the feedstock were also analyzed. The effect volume heating of inedible waste in the electromagnetic field is achieved due to penetration of the field into the feed to a considerable depth. At a certain depth of penetration it becomes possible to prove the form of processed raw material in resonator depending upon the requirements of the process and electromagnetic field parameters. The temperature and conductivity of the material greatly influence to the penetration depth.

Analytical modeling and sensitivity analysis of dielectric-modulated junctionless gate stack surrounding gate MOSFET (JLGSSRG) for application as biosensor

An analytical model of dielectric-modulated junctionless gate-stack surrounding gate MOSFET for application as a biosensor is presented. An expression for the channel-center potential is obtained by solving the 2-D Poisson's equation using a parabolic-potential approach. An analytical model for the threshold voltage is developed from the minimum channel-center potential to analyze the sensitivity of the biosensor. Moreover, the effects of the variation of the different device dimensional parameters on the sensitivity of the biosensor were investigated in order to study the dielectric modulation effects due to the permittivity changes by the biomolecules present within the nanogap cavity. The analytical model is verified and validated with the help of TCAD device simulations.

Effect of biased electric field on the properties of ferroelectric-dielectric composite ceramics with different phase-distribution patterns

Three series of composite ceramic systems including 85 vol% Ba0.5Sr0.5TiO3 - 15 vol% MgO, 78 vol% Ba0.45Sr0.55TiO3 - 22 vol% Mg2TiO4 and 48 vol% Ba0.4Sr0.6TiO3 - 52 vol% BaWO4 were synthesized by solid-state reaction. The diphase ceramics transformed from layer-like pattern and column-like one to final sphere-like one with prolonging the milling time of raw materials from 5 min to 24 h. The dielectric permittivity and tunability of diphase ceramics were improved significantly by the change of phase-distribution patterns. The dielectric permittivity of composite system shows a variation with the applied DC bias field. The Curie temperature was increased while the dielectric peaks were suppressed and broadened as increasing the DC bias field. The tunability presents a maximum value near the ferroelectric-paraelectric phase transition point. The trend of tunability slightly lags behind the change of dielectric permittivity. The comprehensive performance of the material is improved with the increase of the uniformity. However, the quality factor Q values were strongly deteriorated. This result is contrary to the ‘intuitive belief’―a prolonged milling time should improve the Q values due to the well uniformity of diphase distribution.