Variation Of Resonant Frequency Research Articles

High sensitivity metasurface sensor for estimating the complex permittivity of ionic liquids

In this paper, a sensor based on a metasurface structure for the complex permittivity of ionic liquids is designed. The structure consists of an F4B substrate with a metal resonance pattern, and a polystyrene foam box is used to contain the ionic liquids to achieve non-contact measurements. The simulation results show that without the presence of the ionic liquids, the sensor can achieve a significant reflection spectrum depth of -37dB at 11.2GHz, after adding the ionic liquids, the sensor can generate different responses depending on the types of ionic liquids in the frequency range of 8-9.3GHz. Furthermore, by employing a characteristic matrix model inversion based on the relationships between the complex permittivity, resonance frequency, and quality factor variations, the standard deviations of the real and imaginary parts of the complex permittivity for seven ionic liquids are estimated to be 0.18 and 0.3, respectively. The estimated results show a good agreement with the standard values obtained from probe measurements. The sensor designed in this paper features a small size, simple structure, and low fabrication cost. With a volume of 0.216 milliliters of the sample, it achieves a high sensitivity of 462.87MHz/ԑʹand frequency detection resolution of 391.57MHz/ԑʹ. It demonstrates excellent discriminatory detection capability for ionic liquids, providing a new direction for the application research of metasurfaces.

Design and simulation of a novel THz patch antenna for early detection of malignant neoplasms

This research presents a novel patch antenna prototype that operates in the THz range for early detection of malignant cancerous cells. The antenna has dimensions of 100 µm × 100 µm and achieves −27.3 dB return loss at an operating frequency of 2.34 THz. The proposed sensor is optimized for a polyimide substrate with a dielectric constant of 3.5 and thickness of 15.7 µm. The prototype’s sensitivity and performance are evaluated by simulating different malignant neoplasms using High-Frequency Simulation Software (HFSS) for five types of breast cancer cells. The results indicate that the variation in resonant frequency and the S21 parameter between malignant cells and healthy breast cells are the primary factors that determine the sensitivity of the prototype. The proposed patch antenna’s high sensitivity and low profile make it a promising solution for the early detection and prognosis of cancerous cells.

Low-cost microstrip sensor based on coupled step line (CSL) resonator for blood plasma glucose determination

In this paper, a microstrip sensor structure was designed and implemented to detect blood glucose levels (BGL) based on changes in resonant frequencies, achieved by creating couplings at sensitive regions. A coupled step line was used to create a sensitive region on the sensor suitable for BGL testing. Transmission matrix theory was employed for the mathematical analysis to obtain the resonant frequency. Received blood samples from 50 different patients were centrifuged, and their serums were extracted to study the performance of the microchip sensor. By placing individual serum samples (50 µl) at the sensitive region of the sensor, the scattering parameters of the sensor were measured to investigate the resonant frequency variation. In addition, the effects of basic blood parameters were analyzed based on the amount of frequency shift. High sensitivity, suitable quality (Q) factor, compact size, and acceptable reproducibility of the measured results are important features of the developed sensor.

Anomalies in the magnetostrictive modulation of love surface acoustic waves

A magnetic surface acoustic wave (SAW) sensor is built by growing a 100 nm galfenol (Fe72Ga28) film by sputtering between the interdigitated transducers of a SAW delay line. Love waves are produced when the shear waves excited on the piezoelectric substrate are guided by a 3.1 μm layer of amorphous SiO2. Due to the magnetostrictive nature of galfenol deposited on top, the application of magnetic fields modulates the propagation of the mechanical excitations along the sensor by the strain coupling. By introducing the delay line in a feedback loop circuit, these changes are studied as resonant frequency variations. Magnetic field cycles of ±40 mT are applied to the sample and the resonant frequency shift is tracked simultaneously. The sensor exhibited hysteretic frequency behavior that depends on the orientation of the applied magnetic field relative to the direction of Love wave propagation. In the configuration in which the wave vector and the applied field form an angle of 45°, the resonant frequency seems to increase with the magnetization induced by the external field. When the wave vector propagation is parallel to the field, two positive peaks appear close to the coercive field of the film, which has not been reported before. This is probably due to a more complex relationship between the acoustic wave and the magnetic state of the film which could be exploited to give rise to new models of magnetic sensors.

Evaluation of electromagnetic characteristics of 3D-printed radar absorbing structures based on three-dimensional period pattern surface

This paper aims to assess the electromagnetic (EM) characteristics of 3D-printed radar absorbing structures (RASs) based on three-dimensional period pattern surface (3D PPS) within the X-band frequency range (8.2–12.4 GHz). The assessment is validated through HFSS software, a 3D printer (Markforged, X7), and a scanning free-space measurement (SFM) system. Firstly, the analysis indicates that the EM characteristics of RASs based on 3D PPS are impacted by impedance matching in the thickness direction and the scattering of EM waves at the edges. The utilization of Onyx (Chopped carbon fiber/Nylon) reveals variations in resonance frequencies and EM wave absorption performance contingent upon the surface shape. Furthermore, significant differences in the variations of EM characteristics are observed even for RASs with the same surface shape but different materials. Secondly, the measurement results of 3D-printed RAS specimens based on PPS using Onyx exhibit similar trends to the analysis results obtained with the SFM system. Ensuring precise measurement results requires specific measurement conditions tailored to each surface shape, along with an examination of the EM characteristic distribution across the entire specimen area. This is crucial due to variations in the size, number, and range of reflected EM waves in the time domain. The analysis and measurement techniques presented in this study hold applicability in designing 3D-printed RASs that demand high EM wave absorption performance, whether under normal or oblique incident EM waves.

Feasibility of Active Reactance Compensator for Autonomously Maximizing Repeater Coil Current of Wireless Power Transfer System Against Variations in Resonant Frequency and Magnetic Coupling Intensity

Feasibility of Active Reactance Compensator for Autonomously Maximizing Repeater Coil Current of Wireless Power Transfer System Against Variations in Resonant Frequency and Magnetic Coupling Intensity

Reconstructing Late Quaternary Paleovalley Systems of Italy Through mHVSR: A Tool for Seismic Hazard Assessment in Modern Coastal Lowlands

AbstractEffective site characterization in highly urbanized coastal lowlands requires accurate stratigraphic and geophysical investigations. In these regions, which typically host shallowly buried paleovalley systems formed in response to Quaternary glacio‐eustatic fluctuations, the marked lithologic contrast between soft sediment paleovalley fills and the adjacent, stiff substrate has the potential to modify earthquake motions, and assessment of critical parameters, such as shear wave velocities (VS) and resonance frequencies (f), should be coupled with detailed stratigraphic architecture. To evaluate the potential of the microtremor horizontal‐to‐vertical spectral ratio (mHVSR) for paleovalley recognition and mapping, we performed mHVSR measurements along the Adriatic coastal plain of Italy, where two paleovalley systems (Pescara and Manfredonia) have been recently identified. In both areas, we detected rapid lateral variations in resonance frequencies and highlighted laterally continuous impedance contrasts. Relying on a robust stratigraphic framework, we carefully evaluated the relation between geological and geophysical data and identified the stratigraphic surfaces responsible for the observed resonances. We derived VS models for the sediment fill, reconstructing the geometry of the two buried paleovalleys. We address the importance of evaluating the geological context when designing microzonation studies, for a reliable interpretation of changes in resonance frequencies.

Identification of microbes using single-layer graphene-based nano biosensors.

Graphene based nano sensors have huge potential in an era of sensor technology. The objective of this study is to create a sensor by investigating the vibration responses of cantilever and bridged boundary conditioned single layer graphene sheets (SLGS) with various attached microorganisms on the tip and at the centre of the sheet. The Parvoviridae, Flaviviridae, and Polyomaviridae biological substances have been comprehensively investigated here. For the Parvoviridae, Polyomaviridae, and Flaviviridae categories of targeted microbes, the sizes are 21nm, 40nm, and 45nm, respectively. The Parvoviridae family has a maximum frequency of 1.87x107 Hz with a cantilever condition and a mass of 4.2441 Zg, and for a bridged condition, it demonstrates a maximum frequency of 1.23x108 Hz with the same mass on armchair SLG (5 5). The data analysis shows that 3.0041 Zg mass of the Mimivirus has the lowest frequency. It demonstrates explicitly that the rate of frequency decreases as the value of mass increases. When compared to chiral SLG, the armchair single layer graphene sheet performs better. The research indicates that the dynamic properties are significantly influenced by the mass of various biological organisms. The application of this sensor will enable the detection of microorganisms or viruses that can be connected to SLG. In this research, the application of Single Layer Graphene (SLG) as a virus sensing device is explored. Atomistic finite element method (AFEM) has been used to carry out the dynamic analysis of SLG. Molecular dynamic analysis and simulations have been performed to see how SLG behaves when employed as sensors for biological entities and when they are exposed to bridged and cantilever boundary conditions. The frequency analysis was performed using ANSYS APDL software. SLG of various chirality has been utilised in the investigation. By altering the applied mass of a biological object, the difference in frequency observed. The idea behind mass detection employing nano biosensors is built on the concept that the stiffness of a biomolecule changes as its mass changes, making the resonant frequency extremely sensitive to that change. A shift in the resonance frequency results from a change in the associated mass on the graphene sheet. The main challenge in mass detection is estimating the variation in resonant frequency driven by the mass of the connected molecule. The SLG-based biosensor has a specific application in the early identification of diseases. The biosensor investigated in this article is novel, whereas the biosensors that are presently on the market operate using the ionization method. The simulations result shows SLG based biosensor's sensitivity considerably faster than an existing one.

Vocal tract shape variation contributes to individual vocal identity in African penguins.

Variation in formant frequencies has been shown to affect social interactions and sexual competition in a range of avian species. Yet, the anatomical bases of this variation are poorly understood. Here, we investigated the morphological correlates of formants production in the vocal apparatus of African penguins. We modelled the geometry of the supra-syringeal vocal tract of 20 specimens to generate a population of virtual vocal tracts with varying dimensions. We then estimated the acoustic response of these virtual vocal tracts and extracted the centre frequency of the first four predicted formants. We demonstrate that: (i) variation in length and cross-sectional area of vocal tracts strongly affects the formant pattern, (ii) the tracheal region determines most of this variation, and (iii) the skeletal size of penguins does not correlate with the trachea length and consequently has relatively little effect on formants. We conclude that in African penguins, while the variation in vocal tract geometry generates variation in resonant frequencies supporting the discrimination of conspecifics, such variation does not provide information on the emitter's body size. Overall, our findings advance our understanding of the role of formant frequencies in bird vocal communication.

All-knitted stretchable dipole antenna: design, fabrication, and effects of yarn alignments on antenna electromagnetic and tensile properties

With the evolution of the Internet of Things, stretchable antennas are playing an increasingly important role in wearable devices and flexible electronics. Typical drawbacks of current stretchable antennas are complex manufacturing processes, inadequate ventilation, and limited flexibility, which negatively impact their comfort and practicality. In this study, an all-knitted stretchable dipole antenna was designed and fabricated. This antenna was breathable and flexible like regular knitted fabric and had a simple manufacturing process. In addition, the effects of two yarn alignment types, namely antenna arms aligned in the course (AaC) and wale (AaW) directions, on antenna electromagnetic properties under tensile stress were investigated. Under unstretched conditions, both antenna AaC and AaW exhibited S11 of less than –10 dB at the operating frequency of 915 MHz, demonstrating good impedance matching performance and omnidirectional radiation characteristics. When stretched along the arm length direction, the frequency variations and strain of antenna AaC and AaW displayed strong linear relationships. Specifically, antenna AaC exhibited a higher sensitivity to the resonant frequency variation induced by strain when compared to antenna AaW. The results suggest that the antenna AaC are a more desirable option to be used as a sensor for human body movement monitoring. This study provides the theoretical basis and experimental foundation for the design and large-scale production of stretchable antennas utilizing textile materials.

Reconfigurable graphene-based multi-input multi-output antenna design for THz applications

This paper presents a compact graphene-based multi-input multi-output (MIMO) antenna for wireless communications operating in frequency band (0.1-10) THz. This work has been performed with four ports microstrip antennas based on 37×88 μm² a silicon dioxide (Sio₂) substrate and copper on the ground layer, with high isolation by a series of unit cells of graphene selected between adjacent patches to reduce the transmission coefficient and antenna size. Graphene's chemical potential will change by changing the connected DC voltage, leading to bandwidth and resonant frequency variation. The simulation has a reflection coefficient is less than -10 dB at (4.5-10) THz of the frequency scale, mutual coupling (-15 dB), and the gain from (4.7-9) THz is (1.6-6.7254) dB. This paper aims to provide wideband, efficient and reconfigurable with simple graphene-based MIMO antenna for THz applications.

Reconfigurable graphene-based multi-input multi-output antenna design for THz applications

This paper presents a compact graphene-based multi-input multi-output (MIMO) antenna for wireless communications operating in frequency band (0.1-10) THz. This work has been performed with four ports microstrip antennas based on 37×88 μm² a silicon dioxide (Sio₂) substrate and copper on the ground layer, with high isolation by a series of unit cells of graphene selected between adjacent patches to reduce the transmission coefficient and antenna size. Graphene's chemical potential will change by changing the connected DC voltage, leading to bandwidth and resonant frequency variation. The simulation has a reflection coefficient is less than -10 dB at (4.5-10) THz of the frequency scale, mutual coupling (-15 dB), and the gain from (4.7-9) THz is (1.6-6.7254) dB. This paper aims to provide wideband, efficient and reconfigurable with simple graphene-based MIMO antenna for THz applications.

Nonlinear dynamics of an artificial muscle with elastomer–electrode inertia: Modelling and analysis

Artificial muscles are dielectric elastomeric system that mimic the response of the natural muscle and are helpful in many bio-mimicking applications. The existing literature is based on the assumption that electrodes are compliant and are focused on materials with greater extensibility than biological matter. The present work deals with the modelling and nonlinear dynamic analysis of dielectric elastomers considering the elastomer–electrode inertia and damping effect for bio-mimicking. The distinguishing point of the proposed work is the appearance of terms related to the elastomer–electrode inertia effect in the governing equation. Further, the biological muscle’s nonlinear elastic behaviour is incorporated using the Fung material model. Equilibrium stretch variation with parameter exhibits cusp catastrophe. The effect of electrode inertia on the equilibria is examined. Single-well and double-well potential energy characteristics are obtained for constant voltage. The basin of attraction illustrates the sensitiveness of system dynamics on the initial state and damping. The system response, when subjected to time-varying voltage, is explored. Multi-frequency response exists due to harmonic, sub-harmonic, and super-harmonic resonance condition. The resonant frequency variation with geometry and inertia is presented. Time-varying voltage may lead to chaotic behaviour illustrated through the bifurcation diagram. The presence of a strange attractor and positive Lyapunov exponent in the chaotic region further justify the existence of chaos. Additionally, chaotic behaviour is obtained in the case of single-well and double-well potential. Also, the existence of similar attractors with same fractal dimension is shown. The inertia effect significantly changes the dynamic characteristic from chaotic to non-chaotic or vice-versa. The mechanical and electrical load may lead to chaotic or non-chaotic behaviour depending on the geometry of the elastomer. The chaotic region’s dependence on the damping value is also obtained. Our results show that electrode inertia significantly impacts the elastomer under quasi-static and dynamic conditions. The proposed work gives a foundation for precisely designing artificial muscle for practical applications like soft robotics, artificial arms, and different prosthetic implants.

A new method to exploit ultrasonic vibrations in deep drawing process

In the deep drawing process of sheet metals, lack of formability and the defects generated as a consequence of friction are two main limiting factors. Using ultrasonic vibration is an impressive way to decrease these limitations. In this paper, the ultrasonic – aided deep drawing process with a novel way of applying radial ultrasonic vibration is presented. The novelty of the presented method is using the bending mode of vibration in the sheet metal and the die using radial ultrasonic vibration. The presented method, contrary to the other techniques of applying ultrasonic vibration, has shown much fewer resonance frequency variations by changing the sheet metal geometry during the process and likewise with a variation of the clearance between the blank holder and the die. For this purpose, the finite element method was used in designing the equipment for the deep drawing process. The experimental test was done on St12 in the presence and absence of ultrasonic vibration. The effect of ultrasonic vibration in the presented method on the wrinkling and thinning defects and likewise the forming forces were experimentally studied. The results indicated the high efficiency of the presenting method in decreasing both the forming forces and the wrinkling and thinning defects. About a 42.3% decrease in the forming forces and a 4.4% decrease in the thinning effect were achieved by applying ultrasonic vibration.

Association of forced oscillation technique measurements with respiratory system compliance and resistance in a 2-compartment physical model

BackgroundThe forced oscillation technique (FOT) may be useful for diagnosis and follow-up of respiratory diseases. It is unclear how global or regional alterations in airway resistance (Raw) and lung compliance (CL) alter FOT measurements. MethodsA 2-compartment physical model of the respiratory system allowed to simulate variations in Raw, CL, and their heterogeneity during tidal breathing in an adult human. Five-Hz respiratory system resistance (Rrs5) and reactance (Xrs5), area of reactance (AX), resonance frequency (Fresp) and intrabreath variation in Rrs5 and Xrs5 were measured by FOT. Frequency dependance of resistance could not be studied in this model. Relationships between model characteristics (Raw, CL, and heterogeneity) and FOT measurements were explored by multiple regression. ResultsRrs5 and intrabreath variation in Rrs5 and Xrs5 strongly associated with model characteristics (R2=0.753, 0.5 and 0.658). Associations of Xrs5, AX, and Fresp with model characteristics were weak (R2=0.214, 0.349 and 0.076). Raw heterogeneity was the main determinant of Rrs5 (Coeff=0.594), AX (Coeff=0.566) and intrabreath variation in Rrs5 and Xrs5 (Coeff=0.586 and 0.732). Regional extremes in Raw strongly determined Rrs5 (Coeff=1.006). Xrs5 did not strongly associate with any model characteristic. ConclusionRaw heterogeneity and maximal regional Raw were the main determinants of FOT measurements, in particular Rrs5. Associations between CL and FOT measurements were weak.

Hybrid metasurface using graphene/graphitic carbon nitride heterojunctions for ultrasensitive terahertz biosensors with tunable energy band structure

Integrating novel materials is critical for the ultrasensitive, multi-dimensional detection of biomolecules in the terahertz (THz) range. Few studies on THz biosensors have used semiconductive active layers with tunable energy band structures. In this study, we demonstrate three THz biosensors for detecting casein molecules based on the hybridization of the metasurface with graphitic carbon nitride, graphene, and heterojunction. We achieved low-concentration detection of casein molecules with a 3.54 ng/mL limit and multi-dimensional sensing by observing three degrees of variations (frequency shift, transmission difference, and phase difference). The favorable effect of casein on the conductivity of the semiconductive active layer can be used to explain the internal sensing mechanism. The incorporation of protein molecules changes the carrier concentration on the surface of the semiconductor active layer via the electrostatic doping effect as the concentration of positively charged casein grows, which alters the energy band structure and the conductivity of the active layer. The measured results indicate that any casein concentration can be distinguished directly by observing variations in resonance frequency, transmission value, and phase difference. With the heterojunction, the biosensor showed the highest response to the protein among the three biosensors. The Silvaco Atlas package was used to simulate the three samples’ energy band structure and carrier transport to demonstrate the benefits of the heterojunction for the sensor. The simulation results validated our proposed theoretical mechanism model. Our proposed biosensors could provide a novel approach for THz metasurface-based ultrasensitive biosensing technologies.

Ultra-fast and high-sensitive tacrolimus solution detection based on microwave biosensor

A microwave biosensor based on a planar low-pass-split ring resonator is proposed for detecting tacrolimus concentrations in solution. The biosensor was used to detect tacrolimus in an aqueous solution and blood samples containing tacrolimus drug concentration. As the concentration of a sample changes, so do its dielectric properties, causing a shift in the resonant frequency and S parameter. The experimental results show that the resonant frequency and insertion loss are highly linearly related to sample concentration for tacrolimus aqueous solution detection (R2 = 0.99). The detection results of real blood samples were similar to those of tacrolimus aqueous solution, with a linear relationship using frequency (R2 = 0.99) and insertion loss (R2 = 0.91),to demonstrate its effectiveness. In addition, the sensor exhibits low limit of detection (LoD) of 0.032 ng/mL. Finally, the frequency detection resolution (FDR) for the concentration variation range of blood samples from tacrolimus is 32.37 MHz/(ng/mL). The higher the FDR value, the higher the sensor’s sensitivity to sample concentration detection and resonance frequency variation, demonstrating the feasibility of a label-free biosensing scheme. This study presents simple method for achieving a microwave biosensor that is both highly sensitive and fast response.

Nonlinear Resonance Characteristics Analysis of DBD Load Based on State Plane Trajectory

Dielectric barrier discharge (DBD) loads and driving converters are widely utilized in low-temperature plasma generation, but their resonant tanks have typical nonlinear characteristics with control issues. The state plane trajectory analysis is used in this article to investigate the resonant behavior of a DBD load. The converter's working principle and state plane modeling are first discussed. The impact of a high-ratio step-up transformer with parasitic capacitance is then explored, and the updated trajectory model is examined. The DBD platform is created to verify the suggested model, and the associated experimental data are provided. The results of the experiment demonstrate that the discharge trajectory is a zone with distinct borders. The trajectory equations can be utilized to calculate the load equivalent capacitance, and the difference in the boundary equivalent capacitance represents the discharge intensity. The pattern of resonant frequency variation with discharge power is given. The impact mechanism of discharge phenomena and resonance characteristics is discussed.

A mathematical approach to estimate micro-displacement of a dental implant using electromagnetic Frequency Response Analysis

The aim of this paper is to formulate a mathematical model of dental prosthetic using single degree of freedom (SDOF) to assess the micro-displacement under electromagnetic excitation. Using Finite Element Analysis (FEA) and values from literature, stiffness and damping values of the mathematical model were estimated. For ensuring the successful implantation of dental implant system, monitoring of primary stability in terms of micro-displacement is crucial. One of the most popular techniques for the measurement of stability is the Frequency Response Analysis (FRA). This technique assesses the resonant frequency of vibration corresponding to the maximum micro-displacement (micro-mobility) of the implant. Among the different FRA techniques, the most common method is the Electromagnetic FRA. The subsequent displacement of the implant in the bone is estimated by equations of vibration. A comparison has been made to observe the variation in resonance frequency and micro-displacement due to varying input frequency ranges of 1–40 Hz. The micro-displacement and corresponding resonance frequency were plotted using MATLAB and the variation in resonance frequency is found to be negligible. The present mathematical model is a preliminary approach to understand the variation of micro-displacement with reference to electromagnetic excitation force and to obtain the resonance frequency. The present study validated the use of input frequency ranges (1–30 Hz) with negligible variation in micro-displacement and corresponding resonance frequency. However, input frequency ranges beyond 31–40 Hz is not recommended due to large variation in micromotion and corresponding resonance frequency.

Magnetodielectric Material Characterization Using Stepped Impedance Resonators

Two resonance-based methods for magnetodielectric (MD) material characterization are presented in this article using stepped impedance resonators (SIRs). A single SIR (SSIR) is initially used to create two spatially separated sensing areas for permittivity and permeability measurements predicated on the resonance frequency variation. Next, a differential-based sensing method, based on resonance frequency splitting, is introduced for permittivity and permeability differential measurements. For this purpose, four spatially separated sensing areas are established on a single resonance structure using a double SIR (DSIR). The presented sensors provide a reliable sensing method for MD characterization and comparison. The proposed sensing methods are validated through numerical analysis based on electromagnetic (EM) simulation and experimental measurement of materials with different intrinsic EM properties.