Resonance Sensor Research Articles

Sensitivity enhancement of guided mode resonance sensors under oblique incidence

The sensitivity of guided mode resonance (GMR) sensors is significantly enhanced under oblique incidence. Here in this work, we developed a simplified theoretical model to provide analytical solutions and reveal the mechanism of sensitivity enhancement. We found that the sensitivity under oblique incidence consists of two contributions, the grating sensitivity and waveguide sensitivity, while under normal incidence, only waveguide sensitivity exists. When the two contributions are constructively superposed, as in the case of positive first order diffraction of the grating, the total sensitivity is enhanced. On the other hand, when the two parts are destructively superposed, as in the case of negative first order diffraction, the total sensitivity decreases. The findings are further supported by FDTD numerical calculations and proof-of-concept experiments.

A Review on Resonant MEMS Electric Field Sensors

Electric field sensors (EFSs) are widely used in various fields, particularly in accurately assessing atmospheric electric fields and high-voltage power lines. Precisely detecting electric fields enhances the accuracy of weather forecasting and contributes to the safe operation of power grids. This paper comprehensively reviews the development of micro-electromechanical system (MEMS) resonant EFSs, including theoretical analysis, working principles, and applications. MEMS resonant EFSs have developed into various structures over the past decades. They have been reported to measure electric field strength by detecting changes in the induced charge on the electrodes. Significant advancements include diverse driving and sensing structures, along with improved dynamic range, sensitivity, and resolution. Recently, mode localization has gained attention and has been applied to electric field sensing. This paper reviews the performances and structures of MEMS resonant EFSs over recent decades and highlights recent advances in weakly coupled resonant EFSs, offering comprehensive guidance for researchers.

A microsystem for in vivo wireless monitoring of plastic biliary stents using magnetoelastic sensors.

With an interest in monitoring the patency of stents that are used to treat strictures in the bile duct, this paper reports the investigation of a wireless sensing system to interrogate a microsensor integrated into the stent. The microsensor is comprised of a 28-μm-thick magnetoelastic foil with 8.25-mm length and 1-mm width. Magnetic biasing is provided by permanent magnets attached to the foil. These elements are incorporated into a customized 3D polymeric package. The system electromagnetically excites the magnetoelastic resonant sensor and measures the resulting signal. Through shifts in resonant frequency and quality factor, the sensor is intended to provide an early indication of sludge accumulation in the stent. This work focuses on challenges associated with sensor miniaturization and placement, wireless range, drive signal feedthrough, and clinical use. A swine specimen in vivo experiment is described. Following endoscopic implantation of the sensor enabled plastic stent into the bile duct, at a range of approximately 17 cm, the signal-to-noise ratio of ~106 was observed with an interrogation time of 336 s. These are the first reported signals from a passive wireless magnetoelastic sensor implanted in a live animal.

Sensitivity enhancement of nonlinear micromechanical sensors using parametric symmetry breaking

The working mechanism of resonant sensors is based on tracking the frequency shift in the linear vibration range. Contrary to the conventional paradigm, in this paper, we show that by tracking the dramatic frequency shift of the saddle-node bifurcation on the nonlinear parametric isolated branches in response to external forces, we can dramatically boost the sensitivity of MEMS force sensors. Specifically, we first theoretically and experimentally investigate the double hysteresis phenomena of a parametrically driven micromechanical resonator under the interaction of intrinsic nonlinearities and direct external drive. We demonstrate that the double hysteresis is caused by symmetry breaking in the phase states. The frequency response undergoes an additional amplitude jump from the symmetry-breaking-induced parametric isolated branch to the main branch, resulting in double hysteresis in the frequency domain. We further demonstrate that significant force sensitivity enhancement can be achieved by monitoring the dramatic frequency shift of the saddle-node bifurcations on the parametric isolated branches before the bifurcations annihilate. Based on the sensitivity enhancement effect, we propose a new sensing scheme which employs the frequency of the top saddle-node bifurcation in the parametric isolated branches as an output metric to quantify external forces. The concept is verified on a resonant MEMS charge sensor. A sensitivity of up to 39.5 ppm/fC is achieved, significantly surpassing the state-of-the-art resonant charge sensors. This work provides a new mechanism for developing force sensors of high sensitivity.

Flexible Hair‐Like Piezoelectric Acoustic Particle Velocity Sensor with Enhanced Sensitivity for Speaker Recognition

AbstractFlexible resonant acoustic sensors exhibit enhanced sensitivity near their resonant frequencies and have attracted increasing interest as essential components for next‐generation human‐machine speech interactions. However, membrane‐based resonant acoustic sensors are bulky owing to the inherently high bending stiffness of the sensing membrane. Inspired by the tiny hair‐based sensitive acoustic receptors of spiders, this study reports a hair‐like piezoelectric resonant acoustic particle velocity sensor (HP‐APVS) that enables highly sensitive sound sensing with a significantly reduced size. The HP‐APVS device is essentially a polyimide cantilever array fabricated using Nb0.02‐Pb(Zr0.6Ti0.4)O3 (PZT) on polyimide and self‐bending processes. The experimental results demonstrate that the HP‐APVS shows a linear response to acoustic particle velocity instead of acoustic pressure, with enhanced sensitivity in the resonance mode. Additionally, the proposed HP‐APVS exhibits an outstanding speaker recognition rate of 95.3% with an error rate reduction of 75% compared with that of a reference commercial microphone, indicating many potential applications in the realms of biometric authentication, voice user interfaces, and other intelligent acoustic electronics.

Detection of Serratia marcescens and Mierococcus lysodeikticus Bacterial Cells Using Cerium Oxide/Transition Metal Dichalcogenides Heterostructure‐Based Surface Plasmon Resonance Sensor

This article explores a novel surface plasmon resonance sensor for detecting the Serratia marcescens and Mierococcus lysodeikticus bacteria cells employing the cerium oxide (CeO2) and transition metal dichalcogenides heterostructure. The proposed sensor is designed based on the Kretschmann configuration, where silver (Ag) is deposited over a prism's surface to excite the surface plasmons. The transfer matrix method and angular interrogation technique are exploited for analyzing the sensor's performance at a wavelength of 633 nm. Firstly, the optimization of the prism and metal film is analyzed by selecting the minimum reflectance, better sensitivity, and quality factor. Secondly, the influence of the proposed structure in the sensor is executed by the performances of different structures, which are made with defined layers. Thirdly, different sensing parameters are analyzed for the considered bacterial cells, resulting in the maximum attained parameters being a sensitivity of 369.40° RIU−1, QF of 151.35 RIU−1, and detection accuracy of 7.57. Finally, the comparative study also shows the noteworthy enhancement using the proposed sensor compared with existing work. Therefore, the proposed sensor can be used as a carrier for detecting the bacterial cells and establishing a new platform for biomolecular and biomedical applications.

Temperature and RI sensing based on micro-structured optical fiber surface plasmon resonance

In this paper, we propose a surface plasmon resonance sensor based on micro-structured optical fiber capable of simultaneous sensing of a liquid refractive index and temperature. The fiber structure comprises four large air holes, with side polishing and rectangular groove processing on one side without air holes. Ag film and α-Fe2O3 film are coated inside the rectangular groove for refractive index sensing. Au film is coated on the inner walls of the two side air holes and filled with polydimethylsiloxane (PDMS) for temperature sensing. The results show that the sensor can achieve sensing of two parameters in two polarization directions. With a refractive index ranging from 1.35 to 1.42 and temperature ranging from 10°C to 100°C, the maximum refractive index sensitivity reaches 28225.7 nm/RIU and the maximum temperature sensitivity reaches −3.64nm/∘C. The sensor features simple structure, easy implementation, and high sensitivity, making it applicable in fields such as biosensing, chemical sensing, and environmental monitoring.

Real‐Time Nuclear Magnetic Resonance Detection Using Maximum Likelihood Estimation with Single‐Shallow‐Nitrogen‐Vacancy Centers in Quantum Heterodyne Measurements

Single‐nitrogen‐vacancy (NV) centers in diamond are highly promising quantum nuclear magnetic resonance (NMR) sensors. However, their exposure to many sources of noise, such as surface impurities, shot noise from avalanche photodiode overlaps, and spin‐state projection errors inherent in quantum systems, limits their usefulness. Often, long measurement durations are required to accumulate sufficient data for NMR signal detection via fast Fourier transform spectrometry. For practical reasons, methods to shorten the necessary accumulation time for NMR signal detection are greatly desired. In this article, an on‐line formulation of maximum likelihood estimation (MLE) signal processing for quantum heterodyne NMR measurements is presented as a step toward this goal. This MLE method reduces the required data accumulation time by orders of magnitude and provides good estimates of target frequency locales in real time. These results are significant to practitioners of NMR detection with single‐NV centers in diamond who require a quick litmus test for potential signals when probing a wide area.

Designing of High-Sensitivity Optical Surface Plasmon Resonance Sensor (OSPRS) for Fast and Accurate Diagnosis of Dengue Virus (DeVs)

Designing of High-Sensitivity Optical Surface Plasmon Resonance Sensor (OSPRS) for Fast and Accurate Diagnosis of Dengue Virus (DeVs)

Blood Biomarker Detection Using Integrated Microfluidics with Optical Label-Free Biosensor.

In this study, we developed an optofluidic chip consisting of a guided-mode resonance (GMR) sensor incorporated into a microfluidic chip to achieve simultaneous blood plasma separation and label-free albumin detection. A sedimentation chamber is integrated into the microfluidic chip to achieve plasma separation through differences in density. After a blood sample is loaded into the optofluidic chip in two stages with controlled flow rates, the blood cells are kept in the sedimentation chamber, enabling only the plasma to reach the GMR sensor for albumin detection. This GMR sensor, fabricated using plastic replica molding, achieved a bulk sensitivity of 175.66 nm/RIU. With surface-bound antibodies, the GMR sensor exhibited a limit of detection of 0.16 μg/mL for recombinant albumin in buffer solution. Overall, our findings demonstrate the potential of our integrated chip for use in clinical samples for biomarker detection in point-of-care applications.

Ultrafast, Fano resonant colorimetric sensor with high chromaticity beyond standard RGB

Fast-responsive colorimetric sensors with a wide color gamut have garnered significant attention for real-time atmospheric monitoring observable to the naked eye. Although swelling medium-based Fabry–Perot cavities, which enable linear resonance shifts with high Q-factors, have been widely suggested, they face limitations such as a restricted color gamut within standard RGB due to subtractive colors and slow response times caused by the top layer blocking, delaying the swelling medium’s equilibrium time. Here, we present two-dimensionally nanostructured Fano resonant colorimetric sensors using a swelling medium with significantly improved responsiveness and color representation beyond standard RGB. The nanostructured Fano resonator is elaborately designed to transform the spectral line shape into a Lorentz state in terms of reflectance, resulting in additive color through controlled coupling parameters of the resonator systems. In addition, the nanostructuring of the surface provides direct channels to water vapors, ensuring fast and strong interaction with the swelling medium. Consequently, the fabricated sensor exhibits a wide color gamut, covering 141% of standard RGB and 105% of Adobe RGB, and demonstrates rapid responsiveness with response and recovery times of 287 ms and 87 ms, respectively.

Microwave planar resonator-based sensor for pharmaceutical tablet-moisture characterization based on complementary symmetric meander line-shaped structure

ABSTRACT This paper presents a microwave planar resonator-based sensor for moisture sensing application. The resonator sensor is designed utilising the Complementary Symmetric Meander Line-Shaped Resonator topology and operated in the S-band with the frequency range of 2.6–3.3 GHz. The main design criteria of this sensor are based on low manufacturing complexity and cost, ease of fabrication and integration with existing equipment, despite its high sensitivity and accuracy. When this sensor is loaded/unloaded with four different Material Under Tests with relative permittivity values varying from 2.3 to 4.3, the electromagnetic simulations were validated against experimental measurements according to the resonant notch frequency of transmission coefficient for the sensor’s material-characterisation performance. The simulated and experimental results show good agreements on the resonant frequencies and demonstrate the sensor’s high performance with a normalised sensitivity of 6%. Resonant frequencies are well correlated with material permittivity using a quadratic-polynomial regression with R 2 = 0.999. Moreover, moisture-content percentages of both dry and moist paracetamol tablets, measured by a loss-on-drying moisture analyser between 1.74% and 17.72%, have good correlation with the sensor’s resonant-frequency shift from on-line measurements. This resonator sensor has exhibited the potential for detecting moisture contents in small-sized materials in various industries.

A low-cost reflection mode operated microwave resonator sensor for angular displacement detection

A low-cost microwave resonator sensor for angular displacement detection is proposed. The sensor uses a strip-loaded dielectric resonator (SLDR) as the key element. The sensor operates in the reflection mode, i.e. by producing a variation in the reflection coefficient (S11) according to the angular position of the SLDR relative to a microstrip transmission line. The primary advantage of the proposed strategy is its fixed-frequency operation enabling the S11 measurement with a low-cost reflectometer, thereby avoiding the costly vector network analyzer (VNA). Design modelling and initial analysis of the sensor are performed with ANSYS HFSS software. To demonstrate proof of concept, a sensor prototype is fabricated and experimentally characterized with a custom-made reflectometer. Results are compared against VNA-based measurements to be in decent agreement. The proposed sensor exhibits 0.43 dB/0 sensitivity over the dynamic range of 00–900.

Two-dimensional valley photonic crystal resonant cavities

Introducing defects in photonic crystals is a common method for manipulating and controlling the propagation of electromagnetic waves. By introducing defects in photonic crystal waveguides, the periodicity of the waveguide structure can be disrupted, local modes can be formed, and resonant cavity functions can be achieved. In this study, we designed two groups of two-dimensional valley photonic crystal waveguides, each of which uses different methods to introduce defects and obtained different resonant cavity structures, and designed a resonant cavity sensor. We conducted a detailed theoretical analysis of the resonant cavity through simulation software. In addition, we fabricated the samples and conducted microwave experiments to demonstrate the accuracy of our theoretical research. Our research provides guidance for the application of photonic crystal devices.

Sensitivity-enhanced plasmonic sensor modified with ZIF-8

ZIF-8 is a typical metal–organic framework (MOF) material, which has great potential for sensor improvement. In this paper, we prepared a high sensitivity surface plasmon resonance (SPR) sensor based on ZIF-8/Au and described the preparation process of the sensor and characterized the samples in detail. The results showed that the synthesized ZIF-8 nanoparticles were uniform with an average diameter of about 50 nm. The performance of the sensor was related to the amount of ZIF-8, which could be controlled by adjusting the number of spin-coating cycles. When the refractive index ranged from 1.3335 to 1.3635, the maximum sensitivity of the sensor reached 3961.36nm/RIU with one cycle of spin-coating, which was 74.05% higher than that of pure Au single-layer film sensor. Furthermore, the feasibility of the proposed sensor for biological sensing was demonstrated by detecting bovine serum albumin (BSA).

High Responsive Microwave Resonator Sensor for Material Characterization

High Responsive Microwave Resonator Sensor for Material Characterization

Multi-parameter simultaneous extraction with a novel microwave sensor based on coupled resonators

This work presents a microwave resonant multi-parameter sensor devoted to the simultaneous extraction of three characteristics of a homogeneous solid sample: its dielectric permittivity, its loss tangent and its thickness. The device is composed of three coupled resonators in two different substrate boards, having the sample between the boards, in a sandwich configuration. Presence of the sample impacts the electrical response of the device, not only influencing resonators, but also by affecting inter-resonator couplings. A method to analyse the response of the device, allowing for the extraction of the desired characteristics of the sample is proposed, as well as an experimental calibration procedure. The model is built upon 990 simulations, calibrated with three reference-samples measurements and then tested over 18 experimental measurements, with good results, thereby validating the multi-parameter sensing approach.

An SPR-Based In Situ Methane Sensor for the Aqueous and Gas Phase.

This paper presents a fast, low-cost, precise methane sensor based on refractive index changes in a cryptophane A (CryptA)-doped polystyrene membrane. For the realization of this sensor, we built a surface plasmon resonance sensor with a refractive index resolution of 4.31 × 10-6 and investigated the optimal membrane thickness, i.e., a polymer layer of sufficient sensitivity with the lowest response time. For a membrane thickness of 760 nm, a limit of detection of 135 ppm and a response time constant of 45 s were found. Despite a comparable refractive index resolution and a higher CryptA content, the limit of detection is 3 orders of magnitude larger than that of a reported prototype. The sensor is capable of quantifying methane in the gas or aqueous phase. However, temperature, humidity, and ethanol vapor highly influence the signal. Although the principle of CryptA-based methane measurement is a promising, fast, and low-cost method, it will not be able to compete with state-of-the-art sensing in its current state.

Dual-parameter fiber optic surface plasmon resonance sensor with narrow FWHM based on an incidence angle adjusting method

We propose a dual-parameter surface plasmon resonance (SPR) sensor based on a simple, and effective incidence angle adjustment method. It is capable of simultaneously detecting the refractive index and temperature of a liquid. For conventional SPR fiber sensors, the resonance dip will be abnormally broadened in the near-infrared band, leading to difficulty in identifying the SPR dip by the spectrometer. The FWHM of the resonance dip depends on the SPR intensity. Therefore, we propose to utilize the bubble structure to change the incidence angle, which can enhance SPR intensity and thus reduce the FWHM of the resonance dip. During our experiments, we investigated the modulation effect of bubble size on the SPR effect. Subsequently, a two-parameter sensor with a narrow FWHM was prepared using PDMS, and the experimental results show that no crosstalk exists between the two sensing channels. This sensor is beneficial for improving the FWHM of SPR dip.

Experimental and numerical investigation of the sensor effect on the acoustic emission during Pencil-lead Break tests on PMMA plates

Pencil leads are broken on PMMA plates at various source-sensor distances to evaluate the influence of the propagation distance and the sensor type on AE signals. The resulting waves are detected using a broadband or a resonant sensor. The ability of five transducers, PKBBI sensor, MICRO80 sensor, MICRO200HF sensor, Nano30 sensor, and WD sensor, to recreate the characteristic forms of plate waves is evaluated. Because of the response spanning between 300 to 400 kHz frequency range, Nano30 and MICRO80 sensors have a bigger magnitude in the S0 mode than in the A0 mode, especially for small sensor-source distances. Their different responses demonstrate why similar test specimens and test settings can provide diverse findings due to the sensor effect, which is significant for the use of AE data in the classification of AE sources. Then, based on the normalization method, we suggest a procedure to acquire equivalent values for the selected descriptors using Laplacian Score and Principle Component Analysis. In order to gain a thorough understanding of the sensor effect through 3D finite element simulation, a comparative analysis is conducted between the perfect contact sensor and the resonant sensor with sensor effect. The sensor effect arises from the convolution of the Fourier Transform of the signal with the sensitivity curve in the frequency domain. By comparing the waveforms in the time and frequency domain, it is useful to determine how the different sensors differ from the AE signals.