Permittivity Measurements Research Articles

Scrutinizing the dielectric properties of dialysis fluid for health monitoring applications

The concept of permittivity properties of dialysate allows the use of electromagnetic sensing techniques in hemodialysis treatment. In this study, we have introduced a method for assessing the adequacy of dialysis, which is based on the dialysate approach. The dialysate-based method offers several advantages, including preventing blood contamination, the absence of the need for the patient’s blood, and convenient application within laboratory settings. The dielectric properties of the dialysis fluid were analyzed using the open-ended coaxial probe technique to investigate the impact of various urea levels. The findings revealed a direct correlation between fluctuations in complex permittivity measurement and urea concentration levels. The measured results can be used to design invasive and non-invasive microwave sensors. However, further practical trials on dialysis fluid are needed.

Spiropyran-based supramolecular elastomers with tuneable mechanical properties and switchable dielectric permittivity.

Silicone elastomers are widely used in various applications, each demanding different properties and functionalities. To be used in such a broad spectrum, silicones with easily tunable or switchable properties are needed. We showed this is achievable with novel metallo-supramolecular polysiloxanes. Poly(dimethylsiloxane-co-3-aminopropylmethylsiloxane) was reacted with an epoxy-modified spiropyran (SP) in the presence of ZnCl2 as a catalyst. We have found that the ZnCl2 allows the formation of metallo-supramolecular polymers with tuneable mechanical propertiers. The influence of the amount of ZnCl2 used on the thermal and mechanical properties of the synthesized materials was investigated by DSC, tensile test, and DMA. The ability of SP to act not only as a physical cross-linker, but also as a molecular switch was investigated by UV-Vis spectroscopy and dielectric permittivity measurements. It was found that depending on the amount of ZnCl2 used, the dielectric permittivity can either increase or decrease after exposure to UV or visible light, respectively. Additionally, the developed materials can be reprocessed similarly to thermoplastic elastomers. Furthermore, their solubility can be manipulated from insoluble in practically any solvent to highly soluble by simply adding ZnCl2.

Tapered CSRR-Based Sensor for Relative Permittivity Measurement With Application to Biomedical Microfluidic Sensing

Tapered CSRR-Based Sensor for Relative Permittivity Measurement With Application to Biomedical Microfluidic Sensing

Are conductivity sensors useless for irrigators? Exploring measurement consistency around soil moisture thresholds relevant to different applications

AbstractThe cheap conductivity‐based sensors favoured by farmers for soil moisture monitoring remain largely ignored by researchers because of their low accuracy, which results in high uncertainty regarding their utility for irrigators. In this work, conductivity measurements were compared with dielectric permittivity measurements in moisture ranges relevant to different applications. The results showed that the permittivity measurements captured moisture variability well (R2 > 0.8) throughout the full range tested (0%–35%), which is consistent with the literature. Conductivity measurements consistently distinguished dry from wet conditions (p < 0.0001) and reflected moisture variability in lower ranges (R2 > 0.5) but not in higher ranges (>20%). This is problematic because important monitoring thresholds such as field capacity and saturation are in the upper moisture ranges. Conductivity measurements were found to lack any meaningful utility in most applications except those relevant to distinguishing dry from wet conditions and indicating lower‐range moisture patterns, such as monitoring in arid environments. This gives some merit to conductivity sensors considering their very low cost if corrosion is minimised. The described evaluation approach is suggested as an example for developers, labs and extension services to better communicate potential sensor utilities and restrictions to practitioners to improve their accessibility to decision support technologies.

Effect of annealing on flexoelectricity in hafnium oxide (HfO2)

Flexoelectricity is universal in all dielectrics, effective at high temperatures, and a promising transduction technique for nanoelectromechanical systems (NEMS). However, as flexoelectricity is still in its early stages, many aspects require further investigation. Understanding how flexoelectricity depends on material parameters like crystallographic phase and how temperature might affect it is important for selecting and optimizing the right material for technological applications. This work studies the influence of high-temperature annealing (and the consequent crystallization) in the flexoelectricity of hafnium oxide (HfO2), a material with significant technological relevance. We measure the flexoelectric coefficient for amorphous (not annealed) and annealed (slightly crystalline) phases of HfO2, with samples annealed in nitrogen or oxygen atmospheres. Our results indicate that the amorphous phase of HfO2 exhibits the highest flexoelectric coefficient (105 ± 10 pC/m), while annealed samples show a significant decrease, with the lowest value in nitrogen-annealed samples (26 ± 4 pC/m). Samples annealed in an oxygen atmosphere improve flexoelectric properties (54 ± 6 pC/m) compared to those annealed in nitrogen. Using cross-sectional imaging, x-ray diffraction, resonance frequency characterization, and relative permittivity measurements, we find that annealing promotes crystallization into the tetragonal phase and increases internal stress within the HfO2 layer, while most other parameters remain constant. We attribute the differences in flexoelectricity from the annealed samples to the quantity of oxygen vacancies in hafnium oxide. These oxygen vacancies in hafnium oxide seem to negatively affect the flexoelectric coefficient. This finding can be applied to optimize materials to enhance their flexoelectric properties.

Microwave Sensors and Their Applications in Permittivity Measurement.

This paper reviews microwave sensors and their applications in permittivity measurement. The detection, diagnosis, classification, and monitoring without contact and invasion have been the subject of numerous studies based on permittivity characteristics tracking. This review illustrates many new types of research in recent years. Firstly, the application background is briefly introduced, and several main measurement methods are presented. An overview of measurement technology in various applications is compiled and summarized based on numerous typical examples. Exciting applications are compared and presented separately, combining resonator sensors with strong electric fields. Furthermore, differential signals represent trends for future applications with strong environmental immunity, an alternative option to expensive measuring equipment. With the alternation of metamaterials, microfluidics technologies, cross-technology, algorithms, and so on, sensors play an exceptionally prominent role in practical and low-cost applications.

In Vivo Measurements of Murine Melanoma's Complex Permittivity Between 500 MHz and 8.5 GHz

In Vivo Measurements of Murine Melanoma's Complex Permittivity Between 500 MHz and 8.5 GHz

Novel HPMC/PEDOT:PSS nanocomposite for optoelectronic and energy storage applications.

This study investigates a class of materials known as polymer nanodielectrics, which are formed by incorporating ceramic fillers into polymers. These materials offer the unique advantage of tunable electrical and optical properties. The research focuses on the incorporation of high-purity stannic oxide nanoparticles (SnO2 NPs) into a ternary blend matrix of hydroxypropyl methylcellulose (HPMC) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) using a solution casting method. Characterization techniques like X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) revealed alterations in the amorphous nature of the HPMC/PEDOT:PSS blend upon the introduction of SnO2 NPs. These analyses also suggest the formation of interactions between the polymer and nanoparticles. Scanning electron microscopy (SEM) images confirmed the successful dispersion of SnO2 NPs on the surface of the polymer blend, particularly at lower concentrations. The optical properties of the nanocomposite films were investigated using UV-vis spectrophotometry. This analysis allowed for the calculation of optical constants like the bandgap and refractive index. The results showed a dual-bandgap structure, with the direct and indirect bandgaps ranging from 4.92 eV to 4.26 eV and 3.52 eV to 1.68 eV, respectively. Electrical characterization using AC conductivity and dielectric permittivity measurements revealed a dependence on the SnO2 NPs concentration within the frequency range of 0.1 Hz to 10 MHz. The relaxation processes and interfacial polarization effects within these nanocomposites are further discussed in the study. At a frequency of 10 Hz, the AC conductivity exhibited a significant increase, rising from 1.85 × 10-12 S m-1 to 1.04 × 10-9 S m-1 upon the addition of 0.7 wt% SnO2 NPs. These findings highlight the multifunctional nature of the developed nanocomposites. They hold promise for various applications, including UV blockers, optical bandgap tuners, and optical coatings in advanced optoelectronic devices. Additionally, their tunable high permittivity suggests potential use as dielectric substrates for next-generation, high-performance energy storage devices.

Polarizing Magnetic Field Effect on Some Electrical Properties of a Ferrofluid in Microwave Field

The complex dielectric permittivity, ε (f, H) = ε′ (f, H) − i ε″ (f, H), in the microwave frequency range f, of (0.1–3) GHz and polarizing field values H, in the range of (0–135) kA/m, was measured for a kerosene-based ferrofluid with magnetite particles. A relaxation process attributed to interfacial type relaxation was highlighted, determining for the first time in the microwave field, the activation energy of the dielectric relaxation process in the presence of the magnetic field, EA(H), in relation to the activation energy in zero field, EA(H = 0). Based on the complex permittivity measurements and the Claussius–Mossotti equation, the dependencies on frequency (f), and magnetic field (H), of the polarizability (α) and electrical conductivity (σ), were determined. From the dependence of α(f,H), the electric dipolar moment, p, of the particles in the ferrofluid, was determined. The conductivity spectrum, σ(f,H), was found to be in agreement with Jonscher’s universal law and the electrical conduction mechanism in the ferrofluid was explained using both Mott’s VRH (variable range hopping) model and CBH (correlated barrier hopping) model. Based on these models and conductivity measurements, the hopping distance, Rh, of the charge carriers and the maximum barrier height, Wm, for the investigated ferrofluid was determined for the first time in the microwave field. Knowledge of these electrical properties of the ferrofluid in the microwave field is useful for explaining the mechanisms of polarization and control of electrical conductivity with an external magnetic field, in order to use ferrofluids in various technological applications in microwave field.

Reconstruction of flame permittivity distribution based on ECT and Lp regularized D-bar method

Abstract The measurement of flame permittivity is significant in obtaining the combustion state. A method of Lp regularized D-bar is proposed in this article, which is used to reconstruct flame permittivity distribution by electrical capacitance tomography (ECT). Firstly, the distribution characteristic of flame permittivity is analyzed using the electric probe method. The simulation model of ECT flame measurement is set up based on the result of flame permittivity distribution. Then, the relationship model between the truncation radius of the D-bar algorithm and noise level is fitted based on the simulation reconstruction results of flame permittivity. The truncation radius of the D-bar algorithm for flame permittivity reconstruction is obtained by the relationship model. The Lp regularization is introduced into the scattering transformation solving of the D-bar algorithm, and the simulation results of flame permittivity reconstruction under different p-values are compared. In the experiment, the reconstruction of flame permittivity by the D-bar algorithm with different truncation radii is compared. The experimental results verify the truncation radius strategy based on noise level. Moreover, compared with L 1 and L 2 regularization methods, Lp regularization combined with the D-bar algorithm is more accurate in the experiment results of flame permittivity reconstruction.

Measurement of Complex Permittivity in 0.11–0.27 THz With a Novel Multichannel-Coupled Open Resonator

Measurement of Complex Permittivity in 0.11–0.27 THz With a Novel Multichannel-Coupled Open Resonator

Enhancing SrBi₂Nb₂O₉ ceramics: The role of neodymium substitution in structural, dielectric, and ferroelectric properties

This study investigates the impact of neodymium substitution for bismuth in SrBi2Nb2O9 (SBN) ceramics, a potential lead-free alternative for ferroelectric applications. X-ray diffraction analysis reveals a decrease in lattice parameters and volume with increasing Nd content. Scanning electron microscopy examines the influence of neodymium on grain morphology, showing a transition from characteristic SBN plate-like grains to a mix of plates and micro-spheres. Dielectric properties are evaluated, showing an increase in room-temperature permittivity for Nd-doped samples compared to the undoped counterparts. Additionally, the influence of Nd doping on relaxor ferroelectric behavior is studied. The Curie temperature (Tc) increases with Nd concentration, while the temperature dependence of relaxation time weakens. Ferroelectric properties exhibit significant changes due to Nd doping. Inverse permittivity versus temperature (ϵr−1 vs. T) measurements suggest an unconventional response, potentially due to lattice strain induced by the larger ionic radius of Nd. The potential influence of doping concentration on the order of the ferroelectric transition is also explored. Overall, neodymium substitution in SBN ceramics enhances their ferroelectric properties, making them promising for advanced electronic applications.

In Situ Wide-Range Permittivity Measurement: Compact, Cost-Effective, and Highly Sensitive Sensor Using Reconfigurable Phase Shifter

In Situ Wide-Range Permittivity Measurement: Compact, Cost-Effective, and Highly Sensitive Sensor Using Reconfigurable Phase Shifter

Electric Response of a Negative Dielectric Anisotropy Nematic Liquid Crystal Doped with Ionic Dopant

The electrical properties measurements have been performed in a homogeneous alignment parallelepiped cell containing 4-methoxy benzylidene- 4-butylaniline (MBBA) liquid crystal doped with 0.02%wt tetrabutylammonium bromide (TBAB). The measurement of the complex permittivity was conducted in the nematic phase, covering a frequency range of 42 Hz to 5 MHz. A new relaxation mode was observed in the low-frequency region, which was not present in pure MBBA. The obtained dielectric dispersion could be fitted using the double Cole–Cole formula to determine the relaxation frequencies. The steady-state current exhibited a nonlinear dependence on the applied voltage, and hysteresis was observed in the transient current-voltage characteristic curve.

A microwave permittivity sensor on a Mach–Zehnder Interferometer of: Spoof surface plasmon polariton waveguides

A microwave Mach–Zehnder Interferometer (MZI) sensor for the permittivity characterization of liquids is presented in this paper. Two spoof surface plasmon polariton (SSPP) waveguide transmission lines (TLs) composed of compact spiral units is utilized in a differential architecture. Loading a dielectric material on the sensing arm induces a phase difference between the two arms, leading to periodic interference dips on the transmission curve. The spectral positions and magnitudes of these dips change with different dielectric materials. Due to the nonlinear dispersion characteristics of the SSPP TL, the proposed SSPP-based MZI sensor achieves improved sensitivity compared with microstrip-based MZI sensor. To validate the sensor’s performance, six different oil samples and a set of adulterated oils were measured, incorporating a polydimethylsiloxane (PDMS) channel on the sensing arm. The variations in the spectral position and magnitude of the interference dip centered at 3.2 GHz are employed to determine the dielectric constants and loss tangents of the tested oils. The sensitivity in measuring the dielectric constant is 3.61 %. The maximum errors for measuring the dielectric constant and the loss tangent are 4.3 % and 6.7 %, respectively. Compared to other sensors for liquid oil detection, the proposed sensor provides a relatively high sensitivity while maintaining a low liquid volume, making it a promising candidate for permittivity measurements of liquid analytes and solid materials with similar dielectric constants.

Influence of Salt Concentration and Type on Dielectric Permittivity of Rocks

Summary Ionic properties and concentration significantly influence the response of brine-saturated rocks to electromagnetic disturbance. However, the dielectric permittivity response of rocks under different ionic conditions is poorly described. This significantly limits the potential information that could be gained from dielectric permittivity measurements about the pore geometry and fluid content. The influence of salt concentration and type on broadband dielectric permittivity must be reliably quantified to enhance interpretation of dielectric permittivity measurements. The main objective of this paper is to quantify the influence of salt type and concentration on dielectric permittivity via experimental measurements and pore-scale simulations. We examine the impact of salt concentration and type on the dielectric permittivity of pore- and core-scale Berea sandstone (BS) samples. First, we perform frequency-domain dielectric permittivity simulations to quantify the response of the pore-scale models to electric field excitation. The frequency-domain dielectric permittivity simulator solves Maxwell’s equations under quasistatic conditions at discrete frequencies. We simulate the dielectric permittivity in the frequency range of 20 MHz to 3 GHz. We perform the simulations in samples saturated with NaCl, KCl, and MgCl2 brines. The salt concentration of the brine solutions ranges between 10 PPT and 100 PPT (parts per thousand). We fully saturate the samples with different brine solutions at varying salt concentrations for the core-scale analysis. In the core-scale domain, we use the brine solutions and salt concentrations assumed in the pore-scale analysis. The dielectric permittivity measurements were conducted using a network analyzer with a high-temperature coaxial probe setup in the frequency range of 300 MHz to 3 GHz. We observed that relative permittivity at 1 GHz increases with increasing salt concentration, irrespective of the brine type. However, the type of salt significantly controls the magnitude of the decrease in relative permittivity. After increasing the salt concentration from 10 PPT to 100 PPT, relative permittivity at 1 GHz increased by 11% and 7% when the samples were saturated with KCl and NaCl brine solutions, respectively; at 20 MHz, the same increase in salt concentration caused rock relative permittivity to increase by only 1% and 5% in the samples saturated with KCl and NaCl brines, respectively. The lower sensitivity of relative permittivity to salt concentration at 20 MHz compared to 1 GHz can be attributed to the combined influence of interfacial and orientational polarizations on rock dielectric permittivity. The impact of salt type on relative permittivity was negligible in samples saturated with 10 PPT brine solutions. Results demonstrated that taking the influence of salt concentration and type into account is critical for reliable interpretation of dielectric permittivity measurements. The novel contribution of this work is the documentation of how the saturating brine type influences the complex dielectric permittivity of the rocks. This work illuminates the extent to which the relative permittivity can be used for petrophysical analysis in cases where the formation brine salt concentration is uncertain. Additionally, the outcomes of this work will contribute to enhanced interpretation of dielectric permittivity measurements in formations with variable salt concentrations of formation water.

LOCAL DIELECTRIC SPECTROSCOPY AND ITS APPLICATION TO POLYMERS

ABSTRACT The advent of nanodielectrics, nanocomposite materials based on a polymeric matrix, and materials with physical properties ruled by interfacial effects in general demands techniques to characterize functional properties on a local scale with high spatial resolution. Scanning probe microscopies (SPMs), in their electrical modes, have emerged as indispensable tools to access physical quantities such as dielectric constant, surface potential, and static charge, with nanometer-scale lateral resolution and with surface selectivity, being influenced mainly by the outermost layer of the specimen. In this tribute, the development of various SPM electrical modes is illustrated, focusing on the measurement of dielectric permittivity and its spectroscopic extension to access the local, frequency-dependent dielectric function (local dielectric spectroscopy [LDS]). The application to nanostructured polymers in the form of ultrathin films, nanometer-scale–separated blends, and self-assembled block copolymer structures is described. LDS appears to be a promising technique for characterizing the electric properties of polymers and their composites as well as other glass formers and nanostructured systems.

Flow-through microfluidic relative permittivity sensor using highly-doped silicon sidewall electrodes

Abstract This paper reports a flow-through sensor for the real-time measurement of the relative permittivity of a flowing fluid. The proposed sensor contains multiple parallel microchannels. Each channel acts as a parallel plate capacitor in which the electrodes are isolated from the fluid. This approach results in a low pressure drop and high sensitivity while the internal volume is only 50 nl. The fabrication technology allows for controllable scaling of the channel geometry. Equally deep microchannels with widths varying between 5 µm and 50 μ m are fabricated. The fabrication technology is compatible with other flow-through sensors, enabling further on-chip integration. The sensor has been characterised using 10 different fluids with relative permittivity values ranging from 1 to 80—including water and water-containing mixtures—at a measurement frequency of 300 kHz. The results show an accuracy within 3% of full scale and the repeated measurements with nitrogen and water show standard deviations of 1.20 and 1.03, respectively.

Structural, Morphology and Electromagnetic Interference Shielding Studies of Multifunctional Hybrids of Low-Density Polyethene with Graphene, Carbon Nanotube and Magnetite

ABSTRACT In this study, we investigate the EMI SE (Electromagnetic interference shielding effectiveness) of novel multifunctional polymer hybrids in the X-band and Ku-band frequencies. Magnetite nanoparticles were synthesized via wet chemical reduction and nanographene was synthesized through chemical exfoliation combined with microwave treatment. Nine different composites were prepared with varying weight ratios of graphene and magnetite. X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed their structural and morphological properties. SEM analysis revealed magnetite particle sizes ranging from 10.05 nm to 29.8 nm. Vibrating Sample Magnetometer (VSM) analysis indicated that the magnetite nanoparticles exhibit super paramagnetic behavior with a magnetic anisotropy constant (K) of approximately 63.9375 × 106 J/m3. Impedance analysis, permittivity and permeability measurements showed frequency-dependent behaviors, with interfacial polarization effects due to magnetite agglomeration. The highest conductivity, observed in the 50:5:37.5:7.5 hybrid, peaked at 8 S/cm at lower frequencies. The 50:5:37.5:7.5 hybrid demonstrated the highest EMI SE of 50.08 dB (99.999019% suppression) in the X-band, which is suitable for advanced EMI-shielding applications.

Understanding error rejection of differential impedance spectroscopy for the in situ characterization of highly conductive fluids

Abstract Differential impedance spectroscopy (DIS) can offer distinct advantages over conventional impedance spectroscopy (IS), particularly for the in situ characterization of highly conductive, corrosive fluids. To enhance the understanding of DIS and determine the conditions under which this method is preferable over conventional IS with fixed electrode positions, error calculations were performed. Two scenarios were analyzed, one accounting solely for random instrument errors and the other including random errors as well as systematic errors from a serial offset impedance. Our analyses reveal that while permittivity measurements of highly conductive media remain challenging regardless of whether a conventional or differential impedance approach is used, DIS enables highly accurate conductivity measurements across a wide frequency and conductivity range. Studying different cell dimensions with equal cell constants revealed that despite the increased influence of systematic errors at small scales, conductivity can still be accurately measured, underscoring the applicability of DIS for microfluidic applications. Other potential parasitic effects, such as those arising from the electromagnetic skin effect, stray capacitances, electrode size, and temperature gradients, are discussed, providing a comprehensive framework for sample characterization with DIS.