Composite Dielectric Structures Research Articles

A highly sensitive flexible pressure sensor based on laser-induced graphene and a composite dielectric structure

Pressure sensors are widely used in aerospace, mechanics, and medical electronics. Among them, capacitive pressure sensors with diversified electrode materials and dielectric microstructures have been extensively investigated for better performance. However, current prevailing construction strategies for pressure sensors mainly involve expensive metal electrodes and the complicated fabrication process for the microstructured dielectric layer. Here, we propose a flexible capacitive pressure sensor based on laser-induced graphene (LIG) and a composite dielectric structure with a quick and straightforward fabrication method. Due to the multiple deformation properties of porous graphene and air chambers, the sensor exhibits a wide working range between 0 Pa to 10.4 kPa, high sensitivity up to 2.52 kPa-1, and a detection limit as low as 1.2 Pa. The simple but precise fabrication approach offers a reliable structure for the sensor, thereby resulting in a rapid response and excellent cycling stability. On the basis of the outstanding comprehensive performance, our pressure sensors display great potential in practical applications such as health monitoring and motion detection.

Broadband Cloaking Obtained Using HOBBIES Optimization [EM Progammer's Notebook

In this article, we describe the notion of a cloak achieved by employing the usual composite dielectrics surrounding a metal cube, a concept that was first presented by Hwang and Chin [1]. Here, we use an optimization procedure to improve on their results and obtain a three-dimensional composite dielectric structure that can achieve a better broadband match than that of [1]. The two structures of interest are an empty metallic waveguide and a metal cube placed inside the same waveguide but surrounded by different-sized dielectric slabs so that the effect of the metal cube in the transmitted fields inside the waveguide will not be much different from the fields that would exist in an empty waveguide. The dimensions and properties of the simple dielectrics making up the different slabs inside the waveguide are optimized using an electromagnetic simulator called Higher Order Basis Based Integral Equation Solver (HOBBIES) [2] so that the waveguide will appear empty by looking at the nature of the transmitted fields from the waveguide loaded with a metallic cube but surrounded by some dielectrics.

Numerical simulations of dielectric properties of composite material with periodic structure

Results of computer simulations and measurements of frequency-dependent dielectric properties of a binary composite material are presented. The studied composite had well-defined 3D periodic structure and was made of paraffin and paper laminate. In the considered frequency range (10 −3–10 3 Hz), both the constituents were characterized by significantly different dispersive properties of complex dielectric permittivities. These frequency-dependent parameters were measured and were used for 3D numerical simulations of the effective dielectric properties of the mixture. The simulations were performed using two methods, the finite-volume method and the finite-element method. Frequency variations of the computed effective complex permittivity of the composite are discussed and are compared with the experimental data. The results of the simulations show that the distributions of the micro-scale electric field and dielectric losses in the volume of the composite material are strongly frequency dependent. This effect is also analyzed using classical models for composite dielectric structures.

Frequency stability of dielectric loaded HTS microwave resonators

High Q dielectric loaded superconducting resonators have many potential microwave applications. A key issue for many of these is the stability with which the resonant frequencies of such resonators may be realised, for use as frequency references etc. We report experiments on a number of different resonator geometries using YBCO thick films as planar shields for composite dielectric structures. The experimental results are analysed and surface impedance data as a function of temperature and frequency is deduced for each superconductor specimen as well as real and imaginary components of the relative permittivity of each dielectric material involved in the resonators. Using these parameters predictions are made for the attainable stability in realistic resonator structures. We compare these predictions with stability requirements for a number of wide ranging and niche applications.

Process Integration and Manufacturasility Issues for High Performance Multilevel Interconnect

ABSTRACTInterconnect delay is shown to be a performance-limiting factor for ULSI circuits when feature size is scaled into the deep submicron region, due to a rapid increase in interconnect resistivity and capacitance. Dielectric materials with lower values of permittivity are needed to reduce the line-to-line capacitance as metal spacing decreases. However, the challenge is to successfully integrate these materials into on-chip interconnects. A new multilevel interconnect scheme has been developed that gives improved performance through insertion of a low-dielectric-constant material between metal leads. A novel polymer/Si02 composite dielectric structure provides lower line-to-line capacitance while alleviating many of the integration and reliability problems associated with polymers in standard interconnect processing.

Some steps toward the automation of the design of composite dielectric structures

Based on the physical mechanisms believed to underlie the ac electrical breakdown of liquid/solid structures, a volume theory of failure is used to justify the application of a semi-empirical cumulative stress criteria for the assessment of dielectric integrity. The method advocated is extended through the use of a complex Laplace equation to permit the analysis of structures having simultaneous capacitive and resistive stress distributions. Computer algorithms are described for automating dielectric design on this basis and case studies provided to illustrate the utility of the techniques advanced.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An assessment of the physical basis for the application of design criteria for dielectric structures

The use of design criteria for assessing the stresses to which composite dielectric structures are subjected implies careful and informed application. The convention required in the application of these criteria is examined in the light of the physical processes expected in an oil/cellulose transformer structure and related to an equivalent stressed-oil-volume theory of breakdown. The magnitude of the stresses implied by such criteria has been gauged from an examination of a number of case studies in which finite-element analysis has been used to determine the cumulative stress characteristic. >

Analysis of anomalous resonance effects in multilayer-overcoated, low-efficiency gratings

A Rayleigh–Fourier method is used in an analysis of anomalous resonance effects on multilayer-overcoated, low-efficiency gratings. The ratio of grating amplitude to wavelength, H/λ, is 0.016. For wavelength-to-grating-period values such that only the specular beam and the −1 diffracted order are reflected from the grating, such H/λ values yield a nominal −1-order efficiency on the order of 2%. However, for carefully selected parameters such that coupling of incident beam energy into guided waves is achieved, the −1-order efficiency may exceed 50% and is accompanied by a corresponding reduction in the specular beam intensity. The range over which this anomalous behavior occurs is quite narrow. Composite dielectric structures of one to ten layers are considered.

Dielectric housings for centimetre-wave antennae. Part 1: Theory of transmission and reflection

General equations are derived for the transmission and reflection of plane electromagnetic waves incident on two parallel semi-reflecting discontinuities. Application of the equations to various systems of dielectric sheets is considered, and a method of extending their validity to oblique incidence is given. A number of cases of particular interest in the design of single and composite dielectric structures for centimetric antenna housings are discussed in detail, and the relevant design data derived.