Metamaterial-based Sensor Research Articles

A triple plasmon-induced transparency terahertz sensor based on graphene metamaterials

A metamaterial-based terahertz sensor design is presented in this paper. The metamaterial unit structure comprises a graphene cross and three sets of graphene strips, which collectively achieve a triple plasmon-induced transparency (PIT) in both polarization directions. The theoretical results based on the Lorentz resonance theoretical model are in good agreement with finite difference time domain (FDTD) simulations. The sensor is polarization-independent and changes in the angle of incidence between 0° and 10° have a negligible impact on the sensing performance. Furthermore, the sensor exhibits a notable slow-light effect, with a maximum sensitivity of 1.65 THz/RIU and a FOM value of 4.74/RIU for the triple PIT, which is superior to that of comparable devices.

Metamaterial enhanced sensor for powder material classification

In this paper, a simple and efficient approach is presented to classify different power materials based on a one port microwave sensor in X-band. This classification focuses on powder materials, unlike prior studies that focused on liquids (castor oil, neem oil, sunflower oil, sesame oil, and mahua oil), this classification represents a shift towards powdered materials. The response of the proposed sensor is enhanced by adding a metamaterial (MTM) unit cell of F-shape to focus electromagnetic waves on the sample under test. This metamaterial-based sensor is designed to differentiate between different types of materials based on the corresponding reflection coefficient. The sample under test is included inside a dielectric box inserted inside a rectangular waveguide. The MTM unit cell is added on the front face of this box towards the direction of the incident wave. The resonance frequency depends on the characteristics of the powder material inside the box. The MTM unit cell enhances this resonance to simplify the process of classification of different materials. The measured results show that the proposed sensor can detect a wide range of powder materials, including clay, cement, sand, and mixtures: cement & sand, and clay & sand. The designed sensor can be used in various applications, including detection and classification of different powder materials in industrial applications.

Design and experimental validation of a metamaterial-based sensor for microwave imaging in breast, lung, and brain cancer detection

This study proposes an innovative geometry of a microstrip sensor for high-resolution microwave imaging (MWI). The main intended application of the sensor is early detection of breast, lung, and brain cancer. The proposed design consists of a microstrip patch antenna fed by a coplanar waveguide with a metamaterial (MTM) layer-based lens implemented on the back side, and an artificial magnetic conductor (AMC) realized on as a separate layer. The analysis of the AMC’s permeability and permittivity demonstrate that the structure exhibits negative epsilon (ENG) qualities near the antenna resonance point. In addition, reflectivity, transmittance, and absorption are also studied. The sensor prototype has been manufactures using the FR4 laminate. Excellent electrical and field characteristics of the structure are confirmed through experimental validation. At the resonance frequency of 4.56 GHz, the realized gain reaches 8.5 dBi, with 3.8 dBi gain enhancement contributed by the AMC. The suitability of the presented sensor for detecting brain tumors, lung cancer, and breast cancer has been corroborated through extensive simulation-based experiments performed using the MWI system model, which employs four copies of the proposed sensor, as well as the breast, lung, and brain phantoms. As demonstrated, the directional radiation pattern and enhanced gain of the sensor enable precise tumor size discrimination. The proposed sensor offers competitive performance in comparison the state-of-the-art sensors described in the recent literature, especially with respect to as gain, pattern directivity, and impedance matching, all being critical for MWI.

A highly sensitive modified triple split ring metamaterial-based sensor for blood sample detection based on dielectric property alteration

This research paper demonstrates a metamaterial (MTM) based sensing technique to detect various blood samples by analyzing their dielectric properties. The performance of this MTM-based sensor is evaluated with the help of mimicked human blood samples that closely resemble the dielectric properties of actual human blood samples. Moreover, the ISM band frequency of 2.4 GHz is chosen as one of the reference resonance frequencies due to its various industrial and medical applications. The resonating patch is developed on the FR-4 substrate with a dimension of 10 × 20 mm2 that provides sharp reference resonances of 2.4 and 4.72 GHz for the spectra of the transmission coefficient with a good quality factor (Q-factor). The MTM sensor can detect the mimicked blood samples with a maximum frequency deviation of up to 650 MHz at 2.4 GHz and up to 850 MHz at 4.72 GHz, with maximum sensitivity of 0.917 and 0.707, respectively. The measured results using the prototype of the sensor support the simulation result with good agreement, indicating high sensing capability. Due to its high sensitivity, figure of merit (FoM), and frequency shifting with dielectric property changes in blood samples, the developed MTM-based sensor can be implemented effectively for quick sensing of infected blood samples and biomedical applications.

A Very Compact Metamaterial-Based Triple-Band Sensor in Terahertz Spectrum as a Perfect Absorber for Human Blood Cancer Diagnostics

A Very Compact Metamaterial-Based Triple-Band Sensor in Terahertz Spectrum as a Perfect Absorber for Human Blood Cancer Diagnostics

Millimeter-Wave Metamaterial-Based Strain Sensor Concept

Millimeter-Wave Metamaterial-Based Strain Sensor Concept

Evaluation of microwave square ring metamaterial-based resonator for glucose detection

This study presents a biosensor working at a frequency of 3.5 GHz, which is designed as a square ring metamaterial resonator. This study aimed to evaluate the impact of blood amount on the metamaterial-based resonator sensor’s sensitivity. The structure was constructed using Rogers-RT5880 material, with an overall area of 85.71 mm × 85.71 mm2. The simulation of the design involved modelling the blood samples using Debye 1st-order equations. The empirical results observed a noticeable shift towards a lower frequency range in the response and changes in the magnitude, corresponding to an increase in the blood sample’s glucose concentration and thickness. Following this, the experiment was designed to corroborate the simulated results. The sensor achieved the highest sensitivity of 0.23 dB per 100 mg/dl change in glucose level when the thickness of blood was 0.1 mm. It was concluded from the results that the increase in the volume of blood increases the sensor’s sensitivity. However, a trade-off mark is necessary in which an optimum sensitivity is achieved with blood volume as minimum as possible so that a noninvasive biosensor can be designed.

Detection of Toxic Gases Using Flexible Metamaterial Absorber at Terahertz Frequencies

The development of technology implies the release of several gases to the environment. These gases, especially toxic ones, have many negative effects on human life and cause many diseases that will adversely affect human health. In this respect, effective and accurate identification of these gases are important in terms of preventing possible damages. In this study, a sensor design that can detect toxic gases using a metamaterial structure operating in the gigahertz frequency range is presented. Metamaterials not found in nature are defined as artificial or synthetic structures and can be used in many applications, including sensors, thanks to their negative index of refraction. Here a metamaterial-based sensor application for the detection of the carbon monoxide, a toxic gas, is investigated. The sensor performance was analyzed by adding 50% and 100% toxic gas to the suggested metamaterial design, and 0.010 and 0.013 THz shifts were obtained in the resonance frequency, respectively. This shift indicates that this structure is a viable candidate in sensor applications for the carbon monoxide.

Unorthodox technique in sensing with the metamaterial-based resonator sensor at millimetre frequencies

A metamaterial-based resonator is presented in this paper for liquid-sensing applications. The designed sensor operates at millimetre-wave (mm-w) frequencies, and it can characterise the samples that may possess identical characteristics. This paper relies on the extracted permittivity of the structure in the characterisation of the samples, mainly liquids. The sensor requires a very small amount of samples for sensing and it is used in distinguishing oil, ethanol, methanol, glycerol and water. A shift in the resonance frequency of about 200 MHz per unit increase in the epsilon value of samples was achieved. The oil sample showed the lowest value in the extracted permittivity value, while water showed the nearest to zero extracted permittivity. This relationship of variation in extracted permittivity parameter with the change in the sample’s epsilon value is found to be linear and reliable regardless of the change in thickness of the sample.

Ultrathin metamaterial-based refractive index sensor for biomedical applications

Abstract This work presented an ultrathin terahertz metamaterial-based sensor in the terahertz region. The suggested design comprised of gold metasurface atop on layer of dielectric spacer and a layer of gold at the bottom. The simulation results display dual frequencies found at 1.04 THz and 2.655 THz with absorptance rate closed to 100%. The suggested design displays sharp peaks and a maximum Q value of 132.75 in the dual-band absorptance profile. Moreover, the suggested sensor displays polarization independence which will eradicate the polarization demand of the device. The dual peaks of the suggested sensor are extremely sensitive to the refractive index variation of surrounding medium. Furthermore, the suggested sensor sensitivity increases up to 0.76 THz RIU−1 and figure of merit (FOM) reaches up to 38 RIU−1 lies between 1 to 2 RI range at 50 μm analyte thickness selected. Additionally, the sensor device has the ability of detection of glucose and malaria infection with high sensitivity and FOM.

A metamaterial-based dielectric sensor for characterization of ethanol/1-pentanol binary liquid mixtures at dual bands

A metamaterial-based dielectric sensor for characterization of ethanol/1-pentanol binary liquid mixtures at dual bands

Metamaterial-Based Sensor Integrating Microwave Dielectric and Near-Infrared Spectroscopy Techniques for Substance Evaluation

A novel era of “smart” sensors is emerging, in which they are being used in combination with artificial intelligence (AI) to achieve a better understanding of the world. Such sensors need to be ubiquitous. Accordingly, they should have miniaturized dimensions and low costs. However, there is a tradeoff between cost and accuracy of the sensors, which should be overcome with the use of new types of sensors and techniques. In this article, a metamaterial-based sensor that performs simultaneous microwave dielectric spectroscopy and near-infrared (NIR) spectroscopy measurements is presented. It uses a planar circular complementary split-ring resonator for dielectric measurement with an optical path, and NIR spectroscopy is performed in the same physical structure. A greater diversity of data can be achieved from the electromagnetic spectrum using the data from microwave dielectric spectroscopy and NIR spectroscopy; thus, it becomes possible to enhance the accuracy of substance identification with fewer samples. The proposed sensor was evaluated for the identification of olive oil adulteration and achieved an accuracy of 100% using only 14 training samples. To achieve this same accuracy, other techniques used for the detection of adulteration in olive oil need more than 50 training samples. Therefore, the proposed sensor needs 72% fewer samples for training classifier algorithms used in olive oil adulteration identification. This implies the reduction of computing requirements and wall clock time. The proposed sensor opens new avenues to perform material characterization and identification using a combination of microwave dielectric and NIR spectroscopies in the same structure.

Body-Centered Double-Square Split-Ring Enclosed Nested Meander-Line-Shaped Metamaterial-Loaded Microstrip-Based Resonator for Sensing Applications.

The strong localization of the electric and magnetic fields in metamaterial-based structures has attracted a new era of radiation fields in the microwave range. In this research work, we represent a double split ring enclosed nested meander-line-shaped metamaterial resonator with a high effective medium ratio layered on a dielectric substrate to enhance the sensitivity for the material characterization. Tailoring a metallic design and periodical arrangement of the split ring resonator in a subwavelength range introduced field enhancement and strong localization of the electromagnetic field. The design methodology is carried out through the optimization technique with different geometric configurations to increase the compactness of the design. The CST microwave studio is utilized for the extraction of the scattering computational value within the defined boundary condition. The effective parameters from the reflection and transmission coefficient are taken into account to observe the radiation characteristics for the interaction with the applied electromagnetic spectrum. The proposed metamaterial-based sensor exhibits high sensitivity for different dielectric materials with low permittivity values. The numerical data of the frequency deviation for the different dielectric constants have shown good agreement using the linear regression analysis where the sensitivity is R2 = 0.9894 and the figure of merit is R2 = 0.9978.

Miniaturized triple notch metamaterial sensor for solid dielectric characterization with improved sensitivity

PurposeThe purpose of this paper is to retrieve the dielectric constant of the material under test (MUT) by using an empirical relationship, which relates the dielectric properties with all three resonant frequencies of the proposed sensor. Each notch of the sensor is analyzed for sensitivity by using 15 different MUTs with relative permittivity ranging from 1.006 to 16.5 with a fixed dimension of 12 mm × 12 mm × 1.2 mm.Design/methodology/approachIn this paper, we present a triple-notch metamaterial-based sensor for the solid dielectric characterization based on a microstrip transmission line and a direct coupled-double split ring resonator (DC-DSRR). The proposed sensor is designed, and its response is measured using a vector network analyzer to verify the concept. The shift in the resonant frequencies of the proposed sensor owing to contact with MUT is depicted as a function of permittivity using the curve fitting tool.FindingsThe proposed sensors have three notches, with the third notch being more sensitive than the first and second notch because of the high resonance frequency. For the first, second and third resonances, the proposed sensor has sensitivity ranges from 4.9% to 14.68%, 8.97% to 23.95% and 15.48% to 29.36%, respectively. The findings of the simulations, measurements and formulations are all in good accord.Originality/valueIn comparison to previous solid dielectric metamaterial sensors, the proposed triple-notch sensor based on a microstrip transmission line and DC-DSRR has the following advantages: it has a simple unit-cell structure and meets the needs of miniaturization, compact size, low cost and improved sensitivity. It determines the relative permittivity using all three notches so that the accuracy of the measurement is enhanced as compared with single- and double-notch sensors.

Highly sensitive metamaterial-based microwave sensor for the application of milk and dairy products.

In this work, a novel, to the best of our knowledge, metamaterial-based microwave sensor is designed, numerically simulated, and experimentally tested for milk and dairy products in the frequency range of 8 to 9 GHz. The proposed structure is composed of copper split-ring resonators printed on Arlon Diclad 527 dielectric substrate. Reflection coefficient S11 was determined by using numerical simulation, and the structure was experimentally tested to validate the sensor at the X band frequency. The material under the test was placed in the sensor layer just behind the proposed structure, and the design was optimized to sense the change in the dielectric constant via resonance frequency shifts. The proposed study was not only used for fat contents and freshness checking of milk, it was also applied to other dairy products such as cheese, ayran, and yogurt. The maximum resonance frequency shift was observed in yogurt to be 140 MHz, and the minimum frequency shift was observed in fresh and spoiled ayran to be around 40 MHz. This work provides a new approach to the current metamaterial sensor studies existing in literature by having novel material applications with new microwave metamaterial sensors.

Dual-band measurement of complex permittivity in a microwave waveguide with a flexible, thin and sensitive metamaterial-based sensor

A dual-band metamaterial-based sensor is proposed to determine the complex dielectric constant of ethanol-methanol mixtures. The original sensor structure incorporates one connected dual H-shaped slot resonators at the center and one H-shaped slot resonator at the left and right sides of a rectangular copper patch to provide two distinct resonance frequencies. Polycarbonate is chosen as the substrate material due to its lightness, flexibility, robustness and transparency. Full-wave simulations of electric field distributions reveal that the dual resonances at 3.7 GHz and 4.6 GHz stem from different parts of the metamaterial. Measurements are carried out with a WR-229 microwave waveguide and the electromagnetic simulation results are confirmed with good agreement. A first-order equation that relates the complex dielectric constant to the shift of resonance frequency and peak attenuation is used to determine the complex dielectric constant of ethanol-methanol mixtures in the vicinity of 3.3 GHz and 4.4 GHz frequencies. A good agreement with the literature values is obtained validating the accuracy of the used model. Experimental results revealed that the frequency detection resolution and sensitivity parameter values of the proposed sensor are 25.3 MHz and 0.73% for the lower-frequency band and 9.6 MHz and 0.22% for the higher-frequency band, respectively. In addition to being able to operate at dual frequencies, the proposed metamaterial-based sensor has high sensitivities for the two resonance frequencies. Moreover, the advantages of the proposed sensor, as being electrically-small, flexible, noncontact and reusable, provide a good option for discrimination of binary liquid mixtures at multiple frequencies.

Liquid metal-based metamaterial with high-temperature sensitivity: Design and computational study

Abstract This article proposes a metamaterial-based temperature sensor with high sensitivity using the thermally tunable liquid metal of mercury. The response of the metamaterial at different temperatures is theoretically investigated. In the merit of the temperature-sensitive thermal expanding of the embedded mercury resonant structure, different absorption peak frequencies can be observed at different temperatures, which enables the proposed metamaterial capability of temperature sensing. The numerical simulations show that the temperature sensitivity of the proposed sensor can reach up to 27.64 MHz/°C within the range of 0–21.8°C. The calculated electric field and surface current distributions illustrate that the high sensitivity is originated from the dual-dipole mode of the resonant structure. Meanwhile, the dependence of the structural dimensions on temperature sensitivity is discussed to optimize the sensor design. The proposed strategy paves a new way for developing temperature sensors with high sensitivity.

Impact of metasurface deformation on the graphene-SrTiO3 pixelated metamaterial-based sensor

Investigation was made of metamaterial configuration having the metasurface comprising pixelated graphene-strontium titanate squared pattern. Apart from the constitutive properties of metasurface, the transmission characteristics of the proposed structure were obtained under different angular deformations (which would happen due to strain) in metasurface as well as the graphene chemical potentials and ambient temperatures. It was found that the configurations yield sharp transmission minima corresponding to various parametric and operating conditions, which undergo red- and/or blue-shifts under varying temperature as well as tuning condition. Apart from this, the metamaterial yields polarization-insensitive transmission characteristic. These features can be exploited in tunable temperature and/or strain sensing devices.

Millimetre-Wave Metamaterial-Based Sensor for Characterisation of Cooking Oils

The characterisation of the cooking oils presents a significant challenge due to minor changes in their dielectric behaviour. In this paper, a new metamaterial-based sensor incorporating a split-ring resonator (SRR) with a microstrip transmission line is presented to characterise cooking oils. The design demonstrates metamaterial characteristics of negative permittivity and permeability simultaneously at the resonance frequency. Furthermore, its operation in the range of millimetre-wave frequencies can further enhance its sensitivity, especially for liquid materials. The sensor’s novelty is the operation at millimetre-wave frequencies that offers a high shift in the transmission coefficient while operating at 30 GHz. The sensor’s performance analysis is undertaken by using six MUTs with dielectric constants ranging from 0.126 to 4.47. The presented structure designed on 12 × 8 mm2 Rogers substrate offers a sensitivity of 1.12 GHz per unit change in dielectric constant. The phase's shift demonstrates a lower percentage error than the amplitude and linearly moves towards higher frequencies with the increase in dielectric constant and tangent loss of MUT. The designed sensor can be prominently useful for detecting liquids' chemical characteristics in chemistry and medicine fields.

Metamaterial-based sensor design using split ring resonator and Hilbert fractal for biomedical application

In this work, a novel approach is presented to design a metamaterial-based sensitive sensor for biomedical applications. The metamaterial-based sensor objective is to differentiate between different types of cancer cell lines (biological cells) based on their electrical properties. The sensor is designed by incorporating a single circular split ring resonator (SRR) and a Hilbert fractal curve. The SRR is designed based on its capacitive and inductive resonance properties, thereby making the SRR a favorable candidate for sensing applications. Moreover, the Hilbert fractal curve is introduced as a defected ground structure to move the resonance frequency of the SSR to lower band, and to increase sensor sensitivity. Different Hilbert curve orders are investigated. The fourth-order Hilbert curve is used in the final design as it showed the optimal performance among other orders. To verify the sensor functionality and selectivity, the proposed sensor is tested on three types of breast cancer cell lines, these are MCF7, MCF-7, and HS578T. Measurement results of the fabricated sensor compared well with simulated results obtained using high-frequency structure simulator (HFSS18).