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Polyimide (PI) has received great attention for high-temperature capacitive energy storage materials due to its remarkable thermal stability, relatively high breakdown strength, strong mechanical properties, and ease of synthesis and modification. In this review, several key parameters for evaluating capacitive energy storage performance are introduced. Subsequently, the properties of the commercially available PIs are presented. Then, the recent development of designing and tailoring all-organic PI-based polymers is discussed in detail, focusing on molecular composition and spatial configuration to enhance dielectric constant, breakdown strength, discharged energy density, and charge-discharge efficiency. Finally, we outline the current challenges and future development directions of PI-based high-temperature energy storage dielectric materials.

Abstract Transmission lines and outdoor substations are replete with various forms of micro energy such as wind energy, solar energy, and electromagnetic energy. There exists micro energy in the forms of mechanical vibrations, temperature differences, and humidity in power distribution equipment. Innovative sensor or monitoring methods are needed to maintain the stability and digitisation of the grid. Unfortunately, there is limited study on the power supply of these sensor systems. Triboelectric nanogenerators, which are environmentally friendly and use simple materials, show excellent performance in environmental nano‐energy collection and self‐powered online monitoring. Therefore, environmental energy collection systems based on triboelectric nanogenerators are one of the selected methods to convert magnetic energy in the magnetic field into electrical energy. A model structure was designed using the contact separation mode, which is one of the four working modes of triboelectric nanogenerators, based on the strength of the magnetic field in the environment. This structure mainly consists of the friction layer, electrodes for current conduction, and connected loads. The research includes a comparison of four inherent electrical outputs of the triboelectric nanogenerator: open‐circuit voltage, short‐circuit current, capacitance, and power. COMSOL Multiphysics software was used for all modelling and simulation of the TENG. This software was used for the design, material selection, and static study of the TENG. When the relative dielectric constant was fixed, the output voltage reached 2.75×103V and the energy reached 0.12μJ. Overall, ideal reference can be provided for researchers studying power supply issues for sensors in complex magnetic field situations and help them design high‐performance TENGs.

Abstract Toughening plays a key role in epoxy resins (EPs) and their composites for high voltage gas‐insulated switchgear (GIL) tri‐post insulators and receives a lot of attention. However, there are still limited research studies on strain and its distribution for the toughened EPs and composites under tension and especially under high electric fields. Herein, the intrinsically toughening mechanism of EPs (toughening ability: EP‐B > EP‐A) and their composites with Al2O3 (toughening ability: EP‐Bcom > EP‐Acom) was explored in terms of chemical characterisation by IR and molecular motion via differential scanning calorimetry and dielectric spectra. A low rigid segment content in EPs contributes to the excellent toughness. Two‐dimensional digital image correlation (2D‐DIC) and three‐dimensional DIC (3D‐DIC) were utilised to probe strain and its distribution in EPs and their composites under tension and electric fields, respectively. EP‐B with more toughness endows it with a larger strain εF under tensile fields and a greater strain amplitude |εE| under electric fields than EP‐A, such as 9278 με at 1 kN, 16.9% greater than EP‐A and 9767 με at 10 kV/mm, 19.3% higher than EP‐A. In addition, all samples show minus strain under electric fields due to compression. With the introduction of Al2O3, EP‐Bcom exhibits a εF of 2870 με at 1 kN, 69.1% lower than that of EP‐B and 49.4% greater than that of EP‐Acom, and it provides |εE| of 5351 με at 10 kV/mm, 45.2% lower than that of EP‐B and 13.2% greater than that of EP‐Acom. Further, samples with more toughness deliver more uniform strain distribution whether under tension or electric fields.

Abstract This research investigated the influence of temperature and humidity on the giant dielectric (GD) properties of 1% indium tin oxide and 1% Ta2O5 co‐doped TiO2 ceramics sintered at different temperatures. A single phase of rutile TiO2 was obtained in all sintered samples. The mean grain size increased with higher sintering temperatures, resulting in ceramics with a relative density exceeding 98%. A uniform dispersion of dopants and major elements was achieved. Remarkably, the dielectric constant increased significantly from 2 × 103 to 3.7 × 104 with a rising sintering temperature, primarily due to the enlarged grain size. Concurrently, the authors observed low loss tangents, ranging from tanδ≈0.016 to 0.024 at 1 kHz. Slight variations in the dielectric constant were observed with temperature from room temperature up to 210°C, while maintaining remarkably low tanδ. The GD properties were attributed to space charge polarisation at internal interfaces and defect dipoles. Further research explored the impact of environmental conditions on dielectric properties. Remarkably, the ceramics exhibited minimal capacitance variations of less than 10% within the relative humidity range of 30%–95% and temperatures from 15 to 85°C, indicating excellent dielectric stability.

This paper presents a comprehensive methodology for the precise calibration of high-voltage capacitance and dissipation factor (DF) bridges. The technique involves meticulous adjustments using a digital high-precision phase and ratio-measuring system to determine correction factors for DF and capacitance measurements. Unlike other methods that are limited to a narrow range, this approach allows calibration across the entire operational working spectrum of any bridge. While the method has been developed up to 1 kHz, its adaptability for future requirements is facilitated by the developed software. This method has been carried out by calibrating a highly accurate bridge for a capacitor ratio of up to 100, with DFs ranging from −0.01 to 0.01 and currents ranging from 0.1 mA to 1 A. Linear correction factors are established, with their accuracies being rigorously quantified. This methodology achieves expanded uncertainties as low as 3.5 µF/F (3.5 ppm) for capacitance and 2.2 × 10−⁶ for DFs, significantly enhancing measurement reliability across diverse high-voltage capacitor applications.

Abstract The authors propose a novel yet simple way of passive beamforming using a liquid antenna. A hemispherical dielectric resonator antenna filled with a dielectric liquid is considered to realise the fundamental TE111 mode, and a small, weighted metal ball is dropped inside the hemispherical container. This metal ball functions as a movable director and passively steers the realised fundamental mode of the DRA always towards the ground. The proposed design finds its applications in static‐subject‐based applications such as indoor base stations, and beam‐stabilisation/pattern‐correction works in case of dynamic‐subject‐based applications. The overall profile of the antenna is 0.60λ0 × 0.60λ0 × 0.19λ0 targeting the ISM band at 2.4 GHz with decent efficiency and far‐field characteristics. The working prototype is developed and experimentally verified.

Abstract Silicone rubber (SiR) is commonly used in reinforced insulation parts for high‐voltage direct current (HVDC) cable accessories due to its excellent insulation, elasticity, and high‐temperature resistance. HVDC cable accessories always suffer from the local electric field concentration due to the electrical conductivity mismatch between reinforced insulation and main insulation, which can ultimately lead to electric breakdown. The non‐linear conductive composites based on SiR have the ability to adaptively adjust the distribution of the electric field in cable accessories. This is expected to solve the problem of localised electric field concentration. The zinc oxide (ZnO) and glycidyl methacrylate (GMA) are used as fillers and grafted modifier respectively to improve the non‐linear electrical conductivity of ZnO/SiR‐GMA composites. The results indicate that grafting GMA can increase electrical conductivity of SiR, while doping ZnO filler enables SiR to have non‐linear conductivity characteristics. The combination of doping and grafting modification of the composites achieves excellent non‐linear conductive properties at lower ZnO filler content. Additionally, the mechanical properties of the modified composites are enhanced. The simulation results indicate that ZnO/SiR‐GMA is the most effective material for homogenising the electric field when used as reinforced insulation for cable intermediate joints.

Recent work studying dielectric materials has produced increases in dielectric permittivity and dielectric loss in dielectric elastomer materials, leading to increased material performance. However, little is known about the aging and breakdown of these materials within a marine environment, which could affect material performance. A basic study of the aging and breakdown of two different state-of-the-art dielectric materials, 3M's Very High Bond (VHB) 4910 and bi-axially oriented polypropylene (BOPP), in a marine environment is completed. To begin, accelerated life tests are conducted to obtain artificially aged samples, aged to a maximum duration of 12 months in distilled water. Cyclic and non-cyclic tensile loading testing are used to characterize the material fatigue of the unaged vs aged samples and to determine how the material properties change over time when exposed to a simulated marine environment. For VHB, aging seems to transition the hyperelastic (non-linear) behavior to purely elastic (linear) behavior. As aging level and stretch rate increase, the point of maximum elongation decreases and elastic modulus increases. Similar observations are noted for BOPP, although the effect of its bi-axial orientation must be considered. An increase in stretch rate causes an increase in elastic modulus, and the effect of aging looks to be dependent on orientation where for the orientation normal to the long axis, the elastic modulus increases as aging increases and for the orientation parallel to the long axes, the elastic modulus decreases as aging increases. For BOPP, orientation plays a greater effect on stress and elastic modulus than aging or stretch rate.

Abstract This article proposes a novel compact wideband dielectric resonator antenna design that incorporates inhomogeneous material distribution in a cubic structure. Specifically, in this design, the cubic dielectric resonator antenna is divided into multiple small blocks, and a continuous genetic algorithm is employed to optimize the material property of each block in order to maximize the radiation bandwidth. As a result, a cubic dielectric resonator antenna with inhomogeneous material distributions is designed and tested. In measurement, the proposed compact dielectric resonator antenna design exhibits 64.9% impedance bandwidth (4.08–8 GHz), considerably higher than the bandwidth of the initial homogeneous dielectric resonator antenna. The maximum system gain achieved over the frequency range is 9 dB at 7 GHz, with a peak measured system efficiency of 90.6%.

Abstract A novel numerical method is introduced for minimising the presence of scattering echoes in the frontal area of a dielectric ellipsoid through the application of the method of auxiliary sources (MAS) method. This approach utilises a Gaussian radio pulse that spans the frequency spectrum from 0 to 6 GHz. The approach involves determining the properties of an ellipsoid, such as its dimensions and a dielectric permittivity, using a specially developed MATLAB software package to make this ellipsoid invisible. This provides a valuable military and defence technology tool, particularly for stealth and invisibility technology applications. It is beneficial for avoiding detection by radar systems utilised for enemy surveillance and identifying concealed objects. This aims to eliminate the need for metamaterials for invisibility cloaking. The suggested methodology has been confirmed through a validation process, which involved a comparison of the outcomes derived from numerical experiments conducted during pulse echo observations using the FDTD method and an analytical solution. MAS offers a notable advantage over other methods and commercial software by significantly reducing computational time for simulating and analysing 3D dielectric objects. This allows for quicker consideration of various parameter scenarios and optimisation for desired outcomes.

Abstract The demand for innovative thermal management materials with superior thermal conductivity and electrical insulating properties has significantly increased with the development of portable and flexible electronic gadgets. Fluorinated graphene (FG) has recently attracted the attention of the scientific community because of its exceptional thermal conductivity and electrical insulating qualities. This work aims to provide a detailed analysis of the structure‐property relationships inherent in FG, including both chemical and physical properties, and to explain the FG manufacturing process. Special attention should be paid to a thorough analysis of the thermodynamic conduction mechanism exhibited by FG, including the effects of corrugation size, fluorine coverage, and fluorine atom distribution on its thermal conductivity. The essay also examines in‐depth the most current and cutting‐edge developments addressing the utilisation of FG as a functional filler in composite‐modified polyimide (PI) materials. Furthermore, it has been noted as a crucial component in answering the needs for possible applications by maximising thermal conductivity and mechanical qualities in FG/PI composites through particular FG structural engineering and increased FG‐PI interaction. As a result, these elements serve as the main focus of ongoing research projects, highlighting important directions for development and investigation.

Abstract Continuous three‐dimensional BaTiO3 (3DBT) ceramic network was prepared by the sol‐gel method using cleanroom wipers as the template. Subsequently, flexible 3DBT/polyvinyl alcohol‐boron nitride nanosheets (PVA‐BNNS) composite dielectric films were facilely fabricated by inversely introducing different BNNS concentrations of PVA‐BNNS solution into the 3DBT network. The results demonstrated that PVA solution effectively embedded into the 3DBT framework through an inverse infiltration process, thereby endowing the material with excellent flexibility. The content of 3DBT in the saturated 3DBT/PVA‐BNNS composite was ∼27 wt% (6.9 vol%). In addition, the 3DBT/PVA‐1.0%BNNS system exhibited an excellent dielectric constant of 17.4 (at 1 kHz), a high breakdown strength of 114.5 kV·mm−1 and an energy density of 2.51 J·cm−3 (at 110 kV·mm−1), being 1.67, 1.58 and 7.17 times higher than those of traditional fabricated 27 wt% nano‐BT/PVA (at 70 kV·mm−1) composite, respectively. What's more, the obtained 3DBT/PVA‐BNNS dielectric film exhibited superior thermal and mechanical stability, indicating potential applications in harsh environments.

Abstract Film capacitors are playing an increasingly important role in power‐related fields, driven by the continuous development of dielectric materials and practical needs. Long‐term accumulation has also led to an increasing wealth of data related to film capacitors. Sonification opens up a new way for people to make good use of data from film capacitors. A framework for sonifying film capacitors data based on TwoTone is presented. Based on the analysis and discussion, it is clear that the sonification results can easily represent the monotonic variation pattern of film capacitors data. What's more, the sonification results increase the possibility that people pay attention to the changing trend of film capacitors data when there is no significant difference in the visual perception of the data. In addition to providing a new way of music generation of electrical equipment, the method proposed is expected to contribute to theory reference in typical scenarios, such as factory calibration of film capacitors, monitoring of film capacitor operation status, and presentation of statistical data of film capacitors' dielectric materials, which will help us to better understand the distribution characteristics of polymer films.

Abstract A series of siloxane‐containing polyimide films (PIS) were prepared by copolymerising with rigid aromatic dianhydride, siloxane diamines and six different aromatic diamines. The effects of siloxane structures, fluorine and imide content, rigid or flexible segment on the heat resistance, moisture absorption, dielectric performance, mechanical and bonding properties were systematically studied. The results show that PIS films maintain good heat resistance with Tg between 292 and 420°C and 5% weight loss temperature higher than 500°C. The moisture absorption and dielectric constant can be significantly reduced due to the presence of siloxanes and fluorinated groups, with the absorption rate as low as 1.2% and dielectric constant of 2.85 at 1 MHz. When measured at 10 GHz, the dielectric constant ranges from 3.10 to 3.50, and dielectric loss varies from 0.0059 to 0.0098. The PIS‐6 film has the best comprehensive performance due to the low imide content, introduction of trifluoromethyl and ether bonds. The peeling strength of bonding PIS‐6 film with a copper foil can reach 9.2 N/cm. It is proven that siloxane‐containing PIS films with high heat resistance, low dielectric and outstanding adhesion are achieved, which can be applied for flexible integrated circuit boards, high‐frequency electronics and microelectronics fields.

In this work, Co0.5Zn0.5LaxFe2-xO4 (0.00 ≤ x ≤ 0.10) spinel ferrites were synthesized using the sol-gel auto-combustion method. X-ray diffraction (XRD) analysis and Rietveld refinement confirmed the presence of a cubic spinel structure. The crystallite size was estimated to be between 17.5 nm and 26.5 nm using Scherrer’s method and 31.27 nm–54.52 nm using the Williamson–Hall (W-H) method. Lattice constants determined from XRD and Rietveld refinement ranged from (8.440 to 8.433 Å and 8.442 to 8.431 Å), respectively. Scanning electron microscopy (SEM) revealed a non-uniform distribution of morphology with a decrease in particle size. The bandgap values decreased from 2.0 eV to 1.68 eV with increasing rare earth (La3+) doping concentration. Fourier-transform infrared (FT-IR) spectroscopy confirmed the presence of functional groups and M-O vibrations. The dielectric constant and dielectric loss exhibited similar behavior across all samples. The maximum tan δ value obtained at lower frequencies. Regarding magnetic behavior, there was a decrease in magnetization from 55.84 emu/g to 22.08 emu/g and an increase in coercivity from 25.63 Oe to 33.88 Oe with higher doping concentrations. Based on these results, these materials exhibit promising properties for applications in microwave and energy storage devices.

This research presents the synthesis of a glycine chlorzoxazone (GC) organic single crystal through a slow evaporation process using a mixed solvent of water and ethanol at room temperature. The crystal's functional group coordination is examined via fourier-transform infrared (FTIR) spectroscopy. The study delves into the linear optical properties through UV–visible spectroscopy, and thermal analyses provide insights into the material's thermal behavior. Optical nonlinearity is confirmed using the Kurtz-Perry powder technique. The investigation extends to the electrical properties of prepared crystals, incorporating a combination of AC and DC electrical studies. This comprehensive approach enhances our understanding of the multifaceted characteristics of synthesized crystal, positioning it as a promising candidate for different electronic and optical applications.

Abstract Ferroptosis is a predominant contributor to graft kidney ischemia‒reperfusion injury (IRI), resulting in delayed graft function (DGF). However, much less is known about the early predicting biomarkers and therapeutic targets of DGF, especially aiming at ferroptosis. Here, we propose a precise predicting model for DGF, relying on the Akirin1 level in extracellular vesicles (EVs) derived from recipient urine 48 h after kidney transplant. In addition, we decipher a new molecular mechanism whereby Akirin1 induces ferroptosis by strengthening TP53‐mediated suppression of SLC7A11 during the graft kidney IRI process, that is, Akirin1 activates the EGR1/TP53 axis and inhibits MDM2‐mediated TP53 ubiquitination, accordingly upregulating TP53 in two ways. Meanwhile, we present the first evidence that miR‐136‐5p enriched in EVs secreted by human umbilical cord mesenchymal stem cells (UM‐EVs) confers robust protection against ferroptosis and graft kidney IRI by targeted inhibition of Akirin1 but knockout of miR‐136‐5p in UM sharply mitigates the protection of UM‐EVs. The functional and mechanistic regulation of Akirin1 is further corroborated in an allograft kidney transplant model in wild‐type and Akirin1‐knockout mice. In summary, these findings suggest that Akirin1, which prominently induces ferroptosis, is a pivotal biomarker and target for early diagnosis and treatment of graft kidney IRI and DGF after kidney transplant.

This paper features an effective and novel method to characterize dielectric materials using the reflected group delay of an over-coupled partially-filled coaxial resonator. The method employs a simple and cost-effective approach by utilizing one-port measurements from a Vector Network Analyzer to determine the dielectric constant and loss tangent of a dielectric material filled inside a coaxial resonator. Simulations using Advanced Design System by PathWave and ANSYS Electronics Desktop are done to test the mathematical model under different scenarios. Based on the results obtained from simulations, the proposed method can determine the dielectric constant and loss tangent with an error of less than 2% and 30% respectively, when operated to have a coupling coefficient in the range of 2.5 to 10. A region of confidence is derived by taking into account the effect of systematic errors to determine the maximum expected error in the calculated values of dielectric constant and loss tangent. The region of confidence describes that the resonator when filled to more than 50% of its capacity to have coupling coefficient greater than 2.5 can determine the dielectric constant and loss tangent of a material with an error of less than 5% and 80% respectively. However, by limiting the value of coupling coefficient the error in the loss tangent can be restricted under 30%. A coaxial resonator is designed and fabricated, and Teflon is tested in order to validate the proposed method. A hollow Teflon rod is tested twice for different values of coupling capacitance to confirm the repeatability of the method. Soil samples with different moisture contents are tested to confirm the capacity of the method in testing different types of materials. Each of the soil sample is tested three times and standard deviation in the calculated values of the dielectric properties re-confirmed the repeatability of the method. The proposed method is considered appropriate to test the dielectric properties of solid materials which can be machined to fit inside the hollow cavity of the resonator and other materials like soils, fine particle solids, grains and liquids.

Polypropylene (PP)-based recyclable materials have attracted tremendous interest for HVDC cable insulation applications due to their superior electrical properties, e.g., high thermal stability and superior recyclability. Compared with crosslinked polyethylene (XLPE), PP-based materials exhibit the advantages of not only higher working temperatures but also facile and efficient cable manufacturing with reduced costs, which are highly desirable in HVDC cable manufacturing. Considering their promising advantages, PP-based materials have received significant attention from both academia and industry in the field of HVDC cable insulation. In order to adopt PP as a cable insulation material, the mechanical flexibility of PP should be improved. However, regulations of the mechanical properties inevitably influences the electrical properties of PP. So extensive research has been conducted on the regulation of the mechanical and electrical properties of PP. This review summarizes the research progress on recyclable PP-based materials for HVDC cable insulation applications. Particular attention is placed on the electrical property regulations and material structure-property relationships. The challenges that remain to be addressed and the opportunities for future studies on PP-based recyclable HVDC cable insulation materials are also presented.

Abstract Recently, demands for high‐performance polymer film capacitors at elevated temperatures have become more urgent. High dielectric constant is essential for dielectric materials to achieve substantial energy density at relatively low electric fields, which is of great significance to practical applications, while improving the permittivity of high‐temperature polymer dielectrics without a remarkable deterioration in other electrical properties still remains a challenge. Here, a polymer nanocomposite containing z‐aligned high‐k nanowires sandwiched by e‐beam evaporation deposited Al2O3 films was developed based on the optimal structure proposed by the phase‐field simulation. It is found that z‐aligned nanowires are more effective in promoting the dielectric constant than random‐aligned ones, and a large increase in dielectric constant is observed at relatively low content of nanofillers. Outer insulating layers effectively suppress the electric conduction and improve the breakdown strength. Consequently, the nanocomposite with only 1 volume fraction of z‐aligned nanowires exhibits a breakdown strength, electrical resistance, and charge–discharge efficiency as high as neat PEI, but more than twice the discharged energy density than it at 150 °C. This study realises the optimal structure predicted by simulation in experiment, obtaining high‐permittivity, high‐temperature nanocomposites at no expense of other electrical properties, and making it possible to achieve high discharged energy density at relatively low electric fields.

Abstract Heat dissipation has become an important challenge and technical bottleneck for the rapid development of high‐frequency microelectronic devices and high‐voltage electrical equipment. Thus, there is a great urgent need for high‐performance intrinsically thermally conductive polymer (ITCP) to realise effective heat dissipation. In recent year, the ITCP has received extensive attention due to excellent overall performances and clear advantages over conventional heat conductive polymer composites. The thermal transport physics and its relation with the multiscale chain conformations in polymers with diverse morphologies are reviewed. Then, the current understanding of how the chemistry of polymers, multiscale chain morphologies and conformations would affect phonon transport and the resulting thermal conductivity (TC) in both amorphous and crystalline polymers to unveil the important chemistry‐structure‐property relationships is discussed and anaysed. The latest advances in engineering ITCP from oriented fibre to bulk amorphous states for a high TC are summarised. Lastly, the challenges, prospects and outlook of ITCP have been proposed. The authors anticipate that the present paper will spire more fundamental and applied research in the intrinsic polymer dielectrics field to advance scientific understanding and industrial applications.

Abstract We have witnessed the flourish of bioelectronics, brain–computer interface, and brain science programme in recent decades. In this review, the up‐to‐date advances of dielectric, piezoelectric, and ferroelectric nanomaterials in the biomedical applications are summarised. Biomolecular detection methods have been developed, including dielectric‐gated field‐effect transistor, dielectrophoresis, non‐linear dielectric response, and optical tweezer. Endogenous bioelectricity is a crucial in cell proliferation, migration, differentiation, intracellular communication, neuronal activity, tissue growth. Piezoelectric and ferroelectric materials can be utilised as energy transducer to monitor physiological signal, such as blood pressure or respiration, and directly stimulate cell differentiation, neuronal regeneration, tissue repairment etc. They can also catalyse the electrochemical reaction of organisms through piezoelectricity. The intrinsic relevance between neuronal and ferroelectric polarisation signals inspires the application of the ferroelectrics in the modern intelligent bioelectronics like the artificial retina.

Abstract The concept of self‐healing dielectric polymers has been heatedly discussed, with the expectation of high damage resistance and longer service time. However, there is still a lack of analysis on the competitive relationship between electrical degradation and self‐healing. The authors discussed this relationship in two stages: the design of self‐healing strategies and the operation of self‐healing polymers. Since the requirements for excellent insulating or mechanical properties are not consistent with the demands for high self‐healing capability, trade‐offs are necessary during the design of self‐healing polymeric systems. In the operation stage of dielectric polymers, some key factors that affect the service lifetime of non‐autonomous self‐healing dielectric polymers are analysed, including the efficiency and repeatability of self‐healing, and the frequency of healing maintenance. For autonomous self‐healing dielectrics, the simultaneous processes of ageing and healing are investigated using a self‐healing epoxy resin based on microcapsules and in situ‐generated radicals. A quicker recovery of insulating properties, in terms of partial discharge magnitude, was observed under appropriate healing voltages. However, the self‐healing ability might vanish when the voltage was too high, verifying the competitive relationship between electrical degradation and self‐healing.

Abstract The flashover threshold (Vflsh) of polymer insulations such as epoxy (EP) in HVDC systems can be augmented by modifying their surface with an appropriate treatment technology. For such purpose, several surface treatment methods such as ion beam, sandpaper and a combination of the two is introduced. Firstly, insulation samples with pure epoxy (EPpure), different ion beam treatment periods (EPion;10, 15, 20 min) and different roughness (EPsand; R1 = 4.23 μm, R2 = 6.34 μm, R3 = 9.21 μm) are prepared on the laboratory scale. Afterward, based on several characterisations, such as surface conductivity, mean surface roughness and potential distribution of these insulations, multi‐modified insulation (EPmulti = EPion‐20 + EPsand‐R3) is prepared. In the end, the Vflsh of each insulation group is measured and compared to examine the effectiveness of the proposed modifications. It is obtained that the Vflsh of the modified insulations augmented dramatically irrespective of the treatment method. The Vflsh of the insulation group EPmulti augmented by 52.66 % which is the highest improvement among all insulation groups. In short, the proposed surface modifications are effective and could be used as references to enhance the insulation strength of polymer dielectrics in HVDC systems.

Abstract Bacterial biofilm is an important factor in bacterial drug resistance. Recently, it has been proved that electret films can inhibit the bacterial biofilm, while its mechanism of action on biofilms is under further investigation. In this work, taking Staphylococcus aureus as an example, the inhibition of positive electret on bacterial biofilm was verified and its mechanism was explained. Two factors have been found to explain the inhibition mechanism of electret on bacterial biofilms. One is probably due to its inhibition of the expression of key genes related to bacterial biofilms induced by the electric field of positive electret, and the other is to prevent the aggregation of bacteria rather than the direct bactericidal effect. The conclusions are expected to be extended to other types of bacteria and expand the application of electrostatic materials in the field of biomedicine.

Abstract The increasing global demand for food due to population expansion has led to the intensification of the agricultural sector. However, this escalation in agricultural production has brought together undesirable consequences as more waste is produced, leading to growing environmental concerns as proper disposal of these wastes is necessary. Valorization of these bio-wastes into dielectric materials offers a promising solution to conventional, non-renewable, yet costly materials. Comprehensive documentation on the development of these wastes into dielectric materials is then necessary to understand their dielectric properties and how these materials behave with the treatments during the fabrication process. This review focuses on the state-of-the-art development of dielectric materials derived from bio-wastes and agricultural waste, which are beneficial for waste management and materials engineering applications. The elemental composition of the waste materials is also discussed in this review to understand its relationship with the dielectric constant. Moreover, the fabrication process for several waste materials into dielectric materials has been provided and compared. This review provides comprehensive information on green materials in the materials engineering industries and can assist in novel studies. It is foreseen that bio-wastes and agricultural wastes can be renewable, sustainable, and low-cost resources for deriving dielectric materials in light of their ease of accessibility.

Abstract Epoxy‐impregnated paper transformer bushings are prone to water absorption due to the presence of water‐attracting moieties in the cellulose chemical structure and epoxy resin, leading to moisture‐induced insulation defects. To understand the mechanism of moisture's impact on epoxy‐impregnated paper, this study developed a testing platform that integrated moisture diffusion, adsorption, and dielectric properties of insulating materials. Insulation specimens made of epoxy resin and epoxy‐impregnated paper were prepared and their water diffusion characteristics were investigated using the Fick diffusion model and the Langmuir model, respectively. The Guggenheim–Anderson–de Boer equation was used to examine the vacuum vapour adsorption characteristics of the materials, providing a theoretical foundation for examining the form of water present within them. The dielectric response of materials with varying moisture levels was then tested to study the effect of water on the dielectric spectrum curve. Using the Extended Derivative Method, the characteristic frequency reflecting the water content of the epoxy‐impregnated paper was extracted. The results demonstrate that 0.01‐Hz characteristic frequency provides superior accuracy for moisture assessment in epoxy resins compared to 50 Hz, and extracting and fitting the relaxation peak characteristic frequency in epoxy‐impregnated paper moisture evaluation yields higher accuracy than using tan δ at the power frequency.

Abstract Polymer dielectrics with excellent thermal resistance and superior energy storage behaviour are extensively demanded with the increasing development of film capacitors applied in hostile environments. In this study, novel diamine with sulfonyl‐containing side chain was designed and synthesised. The corresponding polyimide (PI) dielectrics derived from the sulfonyl‐containing diamine were prepared, so were the polyimides possessing the same backbone but without side chains. Consequently, superior thermal resistance of glass transition temperature ranged from 162–208°C was obtained. Moreover, the polyimides presented permittivity of 3.34–5.89 at 1 kHz, Weibull breakdown strength of 377–538 MV/m and discharged energy density of 3.82–5.85 J/cm3. In particular, sulfonyl‐containing polyimide of SPI‐2 with flexible backbone and sulfonyl side chain indicates the highest discharged energy density and charge‐discharge efficiency simultaneously. The introduction of the strong polar sulfonyl group in the side chain enhances dielectric and energy storage properties effectively. In addition, it is found that the dipolar moment density (μ/Vvdw) calculated from molecular simulation is closely correlated to permittivity measured from experiments. The combined method of molecular simulation and experiments would offer an effective approach to assist in molecular design of high‐performance polymer dielectrics.

Abstract A series of high‐performance linear and cross‐linked polyimide (PI) aerogels with different molecular structures have been successfully synthesised using the freeze‐drying process. In this study, the comprehensive regulation of microstructure, thermodynamic, thermal insulation and dielectric properties of PI aerogels are achieved by controlling the rigid/flexible structure and composition of polymerised monomers. The increase in rigidity of PI molecular structure could promote the formation of denser pores, which is beneficial to improve the thermodynamic and thermal insulation properties of aerogels. Notably, the cross‐linked PI aerogel prepared by introducing cross‐linking agent (tris(4‐aminophenyl) amine, [TPA]) into linear PI exhibits high thermal stability (Td5% > 560°C), excellent ultralow permittivity (εr = 1.31, f = 106 Hz) and good thermal insulation property (k = 0.056 W/m · K). This innovative strategy promotes the wider application of the cross‐linked polyimide aerogel in the field of integrated circuits and aerospace exploration.

Abstract In many physics and engineering applications requiring exceptional precision, the presence of highly reflective coatings with low thermal noise is of utmost significance. These applications include high‐resolution spectroscopy, optical atomic clocks, and investigations into fundamental physics such as gravitational wave detection. Enhancing sensitivity in these experiments relies on effectively reducing the thermal noise originating from the coatings. While ion beam sputtering (IBS) is typically employed for fabricating such coatings, electron beam evaporation can also be utilized and offers certain advantages over IBS, such as versatility and speed. However, a significant challenge in the fabrication process has been the limitations of the quartz crystal monitor used to measure the thickness of the deposited layers. This paper showcases how, through hardware and software upgrades, it becomes achievable to create high‐density coatings with layers as thin as a few angstroms by using electron beam evaporation (OAC75F coater) with a deposition rate of 1 Å/s and ion‐assisted source with a gas mixture of oxygen and argon, using a pressure of about 4 × 10−4 mbar. Furthermore, these upgrades enable the attainment of high levels of precision and uniformity in the thickness of the coatings.

Abstract Bacterial biofilm formation is an important factor in bacterial resistance. The commonly used methods to inhibit bacterial biofilms are synthetic drugs such as antimicrobial peptides, but physical methods are often safe, non‐toxic and simple to prepare. This work proposes an environmentally friendly method to use electret films to provide a stable electric field during the formation of bacterial biofilms, inhibit the formation of bacterial biofilms through the action of the electric field and weaken the adhesion of bacterial biofilms. The total amount of Staphylococcus aureus biofilm decreased by 20% compared to the control group after the treatment of positive electret. The distribution of exopolysaccharides showed that the activity of biofilm also decreased. In addition, the negative electret can also inhibit the formation of bacterial biofilm. The result can be generalised to other Gram‐positive bacteria and could contribute to reduce the resistance of bacteria, improve the effect of related antibiotics, reduce the dosage of antibiotics and reduce the side effects of drugs.

This study presents the dielectric properties of a barium titanate–gadolinium ferrite composite material, obtained through a solid-state reaction method. The aim of this research was to create a composite material with enhanced dielectric properties compared to each individual component, and to investigate the electrical properties of the composites, using impedance spectroscopy. The structural and morphologic properties were analyzed using X-ray diffraction and scanning electron microscopy, respectively. Impedance spectroscopy measurements were performed over a wide frequency range (100–0.1 GHz) and temperature (45–170 °C) to evaluate the electrical behavior of the material. The dielectric relaxations were analyzed using the Havriliak–Negami function, and the key electrical parameters such as relaxation frequency, dielectric strength, and electrical conductivity were extracted. Several relaxation processes were identified, which depend on the mixture of the initial titanate and ferrite materials, and a correlation between structural, morphologic, and electrical properties was exposed. The sample with the highest dielectric constant was the 25 wt% gadolinium ferrite composite, with ε′ close to 240 and loss tangent values below 0.1, affording it the more appropriate composition for energy storage devices such as lead-free dielectric capacitors.

Abstract Here, the multibranch linear–linear basis function (MB‐LL) is applied to the Poggio–Miller–Chang–Harrington–Wu–Tsai equation for calculating the scattering problem of multi‐scale dielectric targets. The MB‐LL basis function replaces the positive and negative triangles of the traditional linear–linear basis function (LL) with multiple branches, so it can be used at the junction of the meshes of different size. By using the MB‐LL basis function, we can easily divide the calculation region into several non‐overlapping regions, which is very suitable for the simulation of multiscale targets. At the same time, the MB‐LL basis function inherits the properties of the LL basis function, which is more accurate than the multibranch Rao–Wilton–Glisson (MB‐RWG) basis function. Numerical examples demonstrate the advantages of the proposed method.

The goal of this study is to fabricate barium-doped strontium titanate nanomaterial utilizing the sol–gel technique and a range of barium nitrate concentrations. Electrical Structural properties, CV, FTIR, and SEM of all samples had been studied. The X-ray diffraction (XRD) results of the samples showed the cubic structure of strontium titanate. The Cyclic Voltammetry (CV) is performed on all the samples in light and dark conditions, the results showed enhanced current in the CV graph with the increase of Barium concentration from 5, 10, 15, and 20%. The increase in absorption characteristics were also observed when the doping of Ba increased. The bandgap was measured through resistivity and a decrease in bandgap was noted. Pure SrTiO3 morphology showed an oval/spherical crystalline phase when the dopant concentration was increased to 20%, the results show an asymmetrical shape. Keithley's source meter was used to measure all samples' dielectric characterization, which included the dielectric constant, dielectric loss, electrical susceptibility, and conductivity. The results revealed a decline in the dielectric characteristics. It was also observed that when the doping concentrations increase, the dependency of the samples on frequency as well as on temperature also increases.

Abstract High‐performance dielectric capacitors are essential components of advanced electronic and pulsed power systems for energy storage. Because of their high breakdown strength and excellent flexibility, polymer‐based capacitors are regarded as auspicious energy storage material. However, the energy storage capacity of polymer‐based capacitors is severely limited due to their low polarisation and low dielectric permittivity. The modified Stöber method was used to construct two types of CNT@SiO2 (CS) one‐dimensional core‐shell structured nanowires with different shell thicknesses. By integrating the procedures of solution mixing, melt blending, hot‐stretching orientation and hot pressing, sandwich‐structured poly (vinylidene fluoride) (PVDF)‐based composites were fabricated. The CS core‐shell nanowires dispersed in the inter‐layer serve as electron donors, leading to a high permittivity, while two PVDF outer layers provide the favourable overall breakdown strength. The insulating SiO2 shell can effectively limit the migration of carriers and keep the dielectric loss at a relatively low level in the composites. The CS/PVDF composite exhibited an enhanced discharged density (~6.1 J/cm3) and breakdown strength (~241 kV/mm) when the interlayer filled with as small as 1 wt% CS nanowires with the SiO2 shell thickness of 8 nm, which is 203% and 18.7 % higher than pure PVDF (~2.01 J/cm3 at 203 kV/mm), respectively. This research presents a practical strategy for designing and fabricating advanced polymer film capacitor energy storage devices.

Abstract Barium titanate (BaTiO3, BT) was co‐doped by solid‐state sintering with niobium pentoxide (Nb2O5) and cobalt trioxide (Co3O4) as dopants. The modified barium titanate containing Nb and Co (BTNC) with larger particle size (0.5–1 μm) and silver powder (Ag) with smaller particle size (25 nm) were co‐filled with polyvinylidene fluoride (PVDF) to prepare (BTNC‐Ag)/PVDF three‐phase composites. The morphology and crystal structure of composites were characterised by scanning electron microscope (SEM) and X‐ray diffraction (XRD), respectively. SEM shows that when the volume ratio of BTNC and Ag in the composite is 4:1, the two fillers have good dispersion in polymer matrix and could intersperse with each other to reduce voids. XRD patterns display that the filling of BTNC and Ag powders was conducive to promoting the enhancement of the diffraction peaks of β phase and γ phase in PVDF. The dielectric properties of the composites are effectively enhanced through the synergistic effect of the micro‐nano bicomponent ceramic BTNC and conductive particles Ag co‐filled polymer PVDF. When the volume ratio of filler (BTNC:Ag = 4:1) to matrix PVDF is 2/1, the dielectric properties of the composite are the best, the dielectric constant reaches 134.1 at 102 Hz and the dielectric loss is 0.04.

Abstract In this paper, a quasi‐optical resonator with new coupling method and parasitic‐mode‐suppressing in 110–170 GHz is proposed. The coupling of terahertz (THz) quasi‐optical resonator in this paper is realized by PCB substrate processing and pressurized flange. At the same time, the parasitic mode is effectively suppressed by slitting the plane mirror to reduce the influence on the main mode during the test. And the fused quartz sample was tested to verify the feasibility of the system for complex dielectric testing of materials in 110–170 GHz.

Abstract Focussing on the insulating material of power transformer—cellulose insulation paper, this paper first introduces the basic characteristics and engineering application background of insulation paper. Then, the research progress of improving the mechanical properties, thermal stability and electrical properties of insulation paper by nano modification in recent years is compared, and the promotion mechanism is analysed. In addition, in practical engineering application, the oil–paper composite insulation system composed of insulation paper and insulating oil is used for the internal insulation of oil immersed transformer. Therefore, the influence of modified insulation paper on the performance of oil–paper composite insulation system is analysed. Finally, the newly reported new insulation paper is introduced, and the future development trend of modification of traditional insulation paper is analysed.

Abstract The agglomeration causes a significant challenge to nanodielectrics. Identification of agglomerates in scanning electron microscopy (SEM) images is an important step of solving this issue. Motivated by the fast development of image recognition in computer vision, we propose a new approach for agglomerates identification in SEM images of nanodielectrics by semantic segmentation, which is more efficient and accurate than traditional methods. Three models based on convolutional neural networks are investigated in this work, namely pixel blocks classification network, full convolutional segmentation network employed with data augmentation and unsupervised self‐encoding network. All three networks can preliminarily identify agglomerates of spherical silica‐based blend polyethylene nanocomposites. The mean intersection over union (mIoU) of pixel blocks classification network is 0.843 and it takes 25 s to process an image. Full convolutional segmentation network only needs 0.059 s to process a sample, with a mIoU of 0.777. Unsupervised self‐encoding network can reach a mIoU of 0.747 at a speed of 5.806 s. According to the amount of data sets, and requirements for different speed and accuracy, three kinds of networks can be flexibly selected.

The main aim of the article is to demonstrate the effectiveness of the use of ground penetrating radars to assess various objects using the example of assessing the current state of highways. The article uses the software developed by the authors and the corresponding mathematical models. The analysis of the results obtained is based on mathematical models that have proven their effectiveness and is time-tested. It should be emphasised that the main problem in assessing roads with non-rigid pavement is associated with a change in the main parameters of the layers – thickness and dielectric constant. Previously, we proposed a scheme for the layer-by-layer determination of the values of the relative permittivity and then - the subsequent determination of the thickness of each layer, starting from the top layer and ending with the base. The paper presents the results of experiments actually carried out by the authors with various GPRs, which not only have different values of the central frequency, but also have significant design differences. In addition, the results of processing real data using the software developed by the authors are presented. As a result, an improved method of signal calibration has been proposed, which makes it possible to increase the reliability of assessing the thickness of road surfaces, as well as other objects.

In this study, elastomer composites, including silicone rubber and barium titanate, were fabricated by mechanical mixing, a low-cost, fast, and easy technique to produce highly dielectric materials. The resulting composites were investigated in terms of their dielectric and mechanical properties in terms of filler percentage in the mixture. Dielectric permittivity measurements were taken using the microwave regime, and uniaxial tensile tests were carried out for the study of the materials’ mechanical properties, while combined experiments were also carried out to investigate potential correlations between them. The experimental results show that barium titanate inclusions in silicone matrix significantly improve the dielectric constant while reducing the mechanical properties of composites. In addition, combined experiments show that the composites exhibit a nearly stable dielectric profile under mechanical deformations. Consequently, mechanically mixed barium titanate–silicone elastomer composites could potentially become a cost-effective alternative in the extensive market for insulating materials and flexible electronics.

This paper studies the feasibility of Microwave Imaging (MWI) for detection of fractures in superficial bones like the tibia, using a simple and practical setup. First-responders could use it for fast preliminary diagnosis in emergency locations, where X-Rays are not available. It may prove valuable also for cases where X-ray are not recommended, e.g., length pregnant women or children. The method is inspired on the synthetic aperture radar technique. A single Vivaldi antenna is used to linearly scan the bone in the 8.3-11.1 GHz frequency range and collect the scattered fields. The system is operated in air, without the need for impractical impedance-matching immersion liquids. The image is reconstructed using a Kirchhoff migration algorithm. A Singular Value Decomposition (SVD) strategy is used to remove skin and background artifacts. To test this technique, a set of full-wave simulations and experiments were conducted on a multilayer phantom and on an ex-vivo animal bone. Results show that the system can detect and locate bone transverse fractures as small as 1 mm width and 13 mm deep, even when the bone is wrapped by 2 mm thick skin.

Abstract Reducing the dielectric constant and loss of cellulose insulation can make the electric field distribution uniform in oil‐paper insulation systems and decrease the heat generation in dielectric materials, thus ensuring a reliable transformer operation. To guide the experimental design from the molecular level, the fluctuation method was introduced into the molecular dynamics simulation to evaluate the static permittivity of cellulose insulation, εs. The correlation between the dynamics parameter mean square displacement (MSD) and dielectric loss induced by orientational polarization, was investigated. The simulation results and experimental values of five types of cellulose insulation were compared to verify the rationality of the proposed method. The results indicated that the simulation values of εs for five models were agreed well with the experimental values in terms of both the magnitude and the variation trend. The simulation time and permittivity of the surrounding medium εRF are two key parameters, which determine the accuracy of the simulation results of εs. Considering the convergence, 15 ns was chosen as the lower limit of simulation time. The reaction field approximation was adopted to calculate the dipole‐dipole interaction instead of true interaction, that is, εRF→∞. The MSD results reproduced the experimental trend in dielectric loss, indicating that the method can qualitatively predict the dielectric loss of cellulose insulation. Hence, these methods are sufficient to guide design experiments and provide a route to understand the mechanism of the change in dielectric properties at the molecular level.

This paper presents the electrical behavior of the top contact/ bottom gate of an organic field-effect transistor (OFET) utilizing Pentacene as a semiconductor layer with two distinctive gate dielectric materials Polyvinylpyrrolidone (PVP) and Zirconium oxide (ZrO2) were chosen. The influence of the monolayer and bilayer gates insulator on OFET performance was investigated. MATLAB software was used to simulate and determine the electrical characteristics of a device. The output and transfer characteristics were studied for ZrO2, PVP and ZrO2/PVP as an organic gate insulator layer. Both characteristics show a high drain current at the gate dielectric ZrO2/PVP equal to -0.0031A and -0.0015A for output and transfer characteristics respectively, this can be attributed to an increase in the dielectric capacitance. Trans conductance characteristics also studied the gate dielectric materials and show the ZrO2/PVP gate dielectric having a higher value from the monolayer, indicating the effect of dielectric capacitance.

Abstract Graphene has attracted scientific interest as a substrate or additive for developing high‐performance stimuli‐responsive materials. Research on graphene‐based polymer dielectric composites has shown an enhanced electroresponsive electrorheological (ER) effect. However, the mechanism behind the enhanced electroresponse is still incompletely understood. Here, an investigation was performed into dielectric polarization and the ER effect of reduced graphene oxide‐supported polyaniline nanoplates by comparing them with pure granular polyaniline and graphene oxide‐supported polyaniline nanoplates based on dielectric spectroscopy and rheologic analysis. We discovered that both anisotropic morphology and electrical properties have dominant roles in the enhanced ER effect of reduced graphene oxide‐supported polyaniline nanoplates, whereas only anisotropic morphology has a dominant role in the enhanced ER effect of graphene oxide‐supported polyaniline nanoplates. The analysis also showed that reduced graphene oxide‐supported polyaniline nanoplates have a good ER response to both DC and AC electric field actions in the wide shear rate region. This is highly desirable for practical engineering applications. Therefore, the analysis reveals the reason for the enhanced ER effect of reduced graphene oxide‐supported polyaniline nanoplates and also may provide a guide for designing high‐performance ER materials for practical engineering applications by combining the advantages of conducting a reduced graphene oxide core and ER active shell.

Abstract Researchers are devoted to developing dielectric elastomers (DEs) with excellent electromechanical properties as an artificial muscle material. The authors report a new class of semi‐interpenetrating network (semi‐IPN) composites that contains siloxane‐modified linear polyurethane (PU) and silicone rubber through reasonable design of polymer structure. The organic‐filler copper phthalocyanine (CuPc) is chemically grafted into the semi‐interpenetrating network as a cross‐linking point and exhibits excellent dispersibility in the matrix. The various properties of the obtained composite films are also evaluated. The dielectric constant (8.65 at 1 kHz) and maximum actuation strain at 30 MV m−1 (5.32%) are significantly higher than those of semi‐IPN composites.

Abstract The dielectric‐coated impedance cylinder configuration is investigated thoroughly with respect to the space‐wave, leaky‐wave and creeping‐wave excitations for all source polarizations. A very high directivity is achieved for the space‐ and leaky‐wave radiation for the antenna structure compared to that from a dielectric cylindrical rod investigated earlier. It is also observed that such high directivity for the dominant‐mode leaky‐wave is accompanied by higher‐order azimuthal harmonics with low attenuation constant contributing to the leaky‐wave pole, instead of the n = 0 harmonic for the previous configuration. A large enhancement in the space‐wave directivity is also achieved, contributed by higher space‐wave harmonics compared to lower‐order azimuthal harmonics for the cylindrical dielectric rod antenna. The space‐wave and leaky‐wave directivities are examined with variation in the design parameters and azimuthal harmonics. The phase and attenuation characteristics of the leaky‐wave are used to evaluate the optimized leaky‐wave structure parameters and appropriate azimuthal harmonics that result in high directivity for the configuration. The creeping‐wave characteristics for the configuration are also investigated, with a relatively stronger creeping‐wave excitation observed for an inductive surface‐impedance.

In this work, we improved the performance of germanium (Ge) channel Charge Trapping MemTransistors (CTMTs) as synaptic device by using Ti-doped HfO2 as charge trapping layer (CTL). We manipulated the amount of Ti dopant within the HfO2 CTL to perform the band engineering by varying the Hf/Ti cycle ratio in atomic layer deposition (ALD). The content of Ti was quantified and the energy band structures of the gate stack was constructed with the aid of transmission electron microscope (TEM) images and X-ray photoelectron spectroscopy (XPS) analysis. We then fabricated the charge trapping capacitors and characterized their memory characteristics such as memory windows. By the implementation of amphoteric trap model, thermal activated electron retention model and advanced charge decay model, the trap distribution of the CTL was extracted. Finally, we fabricated the CTMTs with Ti-doped HfO2 as the CTL and characterized their performance as synaptic device such as nonlinearity of depression and potentiation and also conductance on/off ratio. We used NeuroSim simulator with multilayer perceptron and convolutional neural network models to evaluate the pattern recognition accuracy of neural network hardware accelerator using CTMTs as synaptic devices and benchmarked the performance of our CTMT with those of other types of synaptic devices.

A novel W-band sensor for complex permittivity measurements of rod shaped samples based on reflectometer method is described. Characterization of dielectric materials around 100 GHz is quite a challenge. The main limitation is the requirements for the accuracy of the dimensions of the test sample and ensuring good contact with conductive surfaces. From this point of view, it seems interesting to use a cylindrical waveguide with the TE01 mode. The four linearly-polarized H10 fields of rectangular waveguides with equal amplitude and phase circumnavigate the cylindrical waveguide to jointly excite its TEnm circular modes with four-fold symmetry. This precludes the excitation of lower-order modes of the metallic cylindrical waveguide. TE01 mode is unique in that its field leads to zero on the surface of the walls of a metallic cylindrical waveguide. The main field interaction takes place on the sample surface. The calibration method uses calibration curves obtained by simulation for known values of complex permittivity of the samples. This eliminates the requirement for a precision calibration standards, which is the problematic to realize at millimeter wavelengths. Moreover, the complex field structure in the sensor makes it impossible to apply a standard calibration method. Simulation and measurements using these method have been performed in W-band (70–114 GHz). Measurement results demonstrate the robustness of this new sensor for characterizing rod shaped dielectric samples.