Resonance Sensor Research Articles

Improving surface plasmon resonance sensors with speckle image processing

This paper investigates digital image correlation approaches for assessing speckle patterns produced by surface plasmon resonance (SPR) imaging. An SPR sensor based on the Kretschmann setup comprising a gold-coated prism in a fixed angular position performs refractive index assessments in ethanol solutions. Subsequently, the acquisition system collects the reflected light and processes the speckle field images to evaluate the sensor's sensitivity, noise, and limit of detection. Based on three repetitions under similar conditions, the maximum resolution for the average intensity, zero-mean normalized cross-correlation, and the relative sum of square differences metrics are 4.90×10−4, 2.31×10−5, and 7.45×10−6 RIU, respectively, leading to an improved limit of detection without modifying the optical setup.

A surface plasmon resonance sensor based on photonic crystal fiber composed of magnesium fluoride and graphene layers to detect aqueous solutions

A surface plasmon resonance sensor based on photonic crystal fiber composed of magnesium fluoride and graphene layers to detect aqueous solutions

Design and Analysis of Surface Plasmon Resonance Sensor with Open-Loop Side-Polished Photonic Crystal Fiber

Design and Analysis of Surface Plasmon Resonance Sensor with Open-Loop Side-Polished Photonic Crystal Fiber

Design and Development of a Split Ring Resonator and Circular Disc Metasurface Based Graphene/Gold Surface Plasmon Resonance Sensor for Illicit Drugs Detection

Design and Development of a Split Ring Resonator and Circular Disc Metasurface Based Graphene/Gold Surface Plasmon Resonance Sensor for Illicit Drugs Detection

Sodium-based no-core fiber surface plasmon resonance sensor with high sensitivity and narrow FWHM

Since fiber-optic sensors using noble metal-excited surface plasmon resonance (SPR) effects have encountered bottlenecks in improving performance, we propose a fiber-optic sensor using sodium in combination with a no-core fiber (NCF) to measure both refractive index (RI) and temperature. We deposited sodium thin films on the surface of NCF optical fibers and protected them with polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS) for RI sensing or temperature sensing. We performed computational simulations and performance analyses of the sensors using the finite element method, and the results show that the sodium-based SPR sensors have higher sensitivity, wider detection range, and narrower full width at half-maximum (FWHM) than the noble metal SPR sensors. SPR sensors with different sodium film thicknesses have different sensing characteristics, so we can get optical fiber sensors with more flexible transmission characteristics, which helps us arrange sensors more conveniently in practical applications. The simulation and numerical results show that when the sensor is used to measure RI, the average sensitivity of the sensor can reach 7977 nm RIU−1, the maximum sensitivity can reach 23100 nm RIU−1, the narrowest FWHM is 14.23 nm, and the maximum figure of merit (FOM) is 719.42 RIU−1 under different thicknesses of sodium film. The corresponding RI ranges from 1.32 to 1.41. When the temperature measurement range is 0 °C ∼ 100 °C, the average sensitivity can reach 7.86 nm °C−1, the maximum temperature sensitivity can reach 21.1 nm °C−1, and the narrowest FWHM is 17.84 nm. In summary, the proposed sodium-based SPR sensor has flexible and high-performance sensing characteristics, and our research work provides more powerful theoretical support for the application of sodium-based plasma devices.

A Self-Temperature Compensation Barometer Based on All-Quartz Resonant Pressure Sensor.

This paper reports a self-temperature compensation barometer based on a quartz resonant pressure sensor. A novel sensor chip that contains a double-ended tuning fork (DETF) resonator and a single-ended tuning fork (SETF) resonator is designed and fabricated. The two resonators are designed on the same diaphragm. The DETF resonator works as a pressure sensor. To reduce the influence of the temperature drift, the SETF resonator works as a temperature compensation sensor, which senses the instantaneous temperature of the DETF resonator. The temperature compensation method based on polynomial fitting is studied. The experimental results show that the accuracy is 0.019% F.S. in a pressure range of 200~1200 hPa over a temperature range of -20 °C~+60 °C. The absolute errors of the barometer are within ±23 Pa. To verify its actual performance, a drone flight test was conducted. The test results are consistent with the actual flight trajectory.

Design and Optimization of MEMS Resonant Pressure Sensors with Wide Range and High Sensitivity Based on BP and NSGA-II.

With the continuous progress of aerospace, military technology, and marine development, the MEMS resonance pressure sensor puts forward the requirements of not only a wide range but also high sensitivity. However, traditional resonators are hardly compatible with both. In response, we propose a new sensor structure. By arranging the resonant beam and the sensitive diaphragm vertically in space, the new structure improves the rigidity of the diaphragm without changing the thickness of the diaphragm and achieves the purpose of increasing the range without affecting the sensitivity. To find the optimal structural parameters for the sensor sensitivity and range, and to prevent the effects of modal disturbances, we propose a multi-objective optimization design scheme based on the BP and NSGA-II algorithms. The optimization of the structure parameters not only improved the sensitivity but also increased the interference frequency to solve the issue of mode interference. The optimized structure achieves a sensitivity and range of 4.23 Hz/kPa and 1-10 MPa, respectively. Its linear influence factor is 38.07, significantly higher than that of most resonant pressure sensors. The structural and algorithmic optimizations proposed in this paper provide a new method for designing resonant pressure sensors compatible with a wide range and high sensitivity.

Noise Tolerant Photonic Bowtie Grating Environmental Sensor.

Resonant photonic refractive index sensors have made major advances based on their high sensitivity and contact-less readout capability, which is advantageous in many areas of science and technology. A major issue for the technological implementation of such sensors is their response to external influences, such as vibrations and temperature variations; the more sensitive a sensor, the more susceptible it also becomes to external influences. Here, we introduce a novel bowtie-shaped sensor that is highly responsive to refractive index variations while compensating for temperature changes and mechanical (linear and angular) vibrations. We exemplify its capability by demonstrating the detection of salinity to a precision of 0.1%, corresponding to 2.3 × 10-4 refractive index units in the presence of temperature fluctuations and mechanical vibrations. As a second exemplar, we detected bacteria growth in a pilot industrial environment. Our results demonstrate that it is possible to translate high sensitivity resonant photonic refractive index sensors into real-world environments.

Harnessing quantum plexcitons for enhanced sensitivity and selectivity of creatinine sensor

Despite their widespread usage, surface plasmon resonance (SPR) sensors have several drawbacks, including limited sensitivity and the requirement for sophisticated functionalization chemistry to enhance their performance. In contrast, using quantum states for sensing may result in an enormous increase in sensor performance. These states, however, often need a rigorously controlled environment, which limits their adoption. Recently, there has been a surge of interest in employing quantum plexcitons to solve this conundrum, which has recently been proven to be resilient and robust even in ambient conditions. Here, we report the utilization of plexcitons induced through hybridization of surface plasmon and excitons in a SPR-Otto configuration for sensing creatinine molecules. Using an organic pentamer, BOBzBT2, the ultra-strong coupling regime with a Rabi splitting of 22 % of the uncoupled energy was observed and exploited to monitor the creatinine concentrations. This demonstration proposes a way to combine the benefits of an SPR-based design with the sensitivity offered by quantum plexcitons, which is beneficial for future practical quantum sensing.

Recent Technologies for Transcutaneous Oxygen and Carbon Dioxide Monitoring.

The measurement of partial pressures of oxygen (O2) and carbon dioxide (CO2) is fundamental for evaluating a patient's conditions in clinical practice. There are many ways to retrieve O2/CO2 partial pressures and concentrations. Arterial blood gas (ABG) analysis is the gold standard technique for such a purpose, but it is invasive, intermittent, and potentially painful. Among all the alternative methods for gas monitoring, non-invasive transcutaneous O2 and CO2 monitoring has been emerging since the 1970s, being able to overcome the main drawbacks of ABG analysis. Clark and Severinghaus electrodes enabled the breakthrough for transcutaneous O2 and CO2 monitoring, respectively, and in the last twenty years, many innovations have been introduced as alternatives to overcome their limitations. This review reports the most recent solutions for transcutaneous O2 and CO2 monitoring, with a particular consideration for wearable measurement systems. Luminescence-based electronic paramagnetic resonance and photoacoustic sensors are investigated. Optical sensors appear to be the most promising, giving fast and accurate measurements without the need for frequent calibrations and being suitable for integration into wearable measurement systems.

A portable surface plasmon resonance (SPR) sensor for the detection of immunoglobulin A in plasma.

A life-threatening anaphylactic shock can occur if a patient with undiagnosed immunoglobulin A (IgA) deficiency (i.e., IgA levels <500 ng/mL) receives IgA-containing blood, hence the need for a rapid, point-of-care (POC) method for IgA deficiency screening. Enzyme-linked immunosorbent assay (ELISA) is routinely used to detect IgA, but this method requires trained specialists and ≥24 h to obtain a result. We developed a surface plasmon resonance (SPR)-based protocol to identify IgA-deficient patients or donors within 1 h. The SPR sensor relies on the detection of IgAs captured by primary antibodies adsorbed on the SPR chip and quantified with secondary antibodies. The sensor was calibrated from 0 to 2000 ng/mL in buffer, IgA-depleted human serum, and plasma samples from IgA-deficient individuals. A critical concentration of 500 ng/mL was set for IgA deficiency. The optimized sensor was then tested on eight plasma samples with known IgA status (determined by ELISA), including five with IgA deficiency and three with normal IgA levels. The limit of detection was estimated at 30 ng/mL in buffer and 400 ng/mL in diluted plasma. The results obtained fully agreed with ELISA among the eight plasma samples tested. The protocol distinguished IgA-deficient from normal samples, even for samples with an IgA concentration closer to critical concentration. In conclusion, we developed a reliable POC assay for the quantification of IgA in plasma. This test may permit POC testing at blood drives and centralized centers to maintain reserves of IgA-deficient blood and in-hospital testing of blood recipients.

Fano resonance and enhanced sensing in the excitation of the surface phonon polariton

The surface phonon polariton is a collective oscillation mode of phonons and incident electromagnetic waves in polar dielectric materials. Compared with the surface plasmon polariton, it has low loss and can be applied to the mid-infrared band. A surface phonon resonance sensor based on waveguide-coupling is proposed. The sensor structure is a typical Kretschmann configuration consisting of a germanium (Ge) prism, a silicon carbide (SiC) layer, an indium selenide (In2Se3) film, a titanium dioxide (TiO2) film, and the surrounding dielectric. The reflectivity possesses significant asymmetric Fano resonance dips. In sensing applications, the waveguide-coupling structure yields a sensitivity by intensity of 11278RIU−1 and a figure of merit of 10344RIU−1. Our investigation provides an alternative method for refractive index sensing, thus opening up opportunities for the design of various phonon devices based on Fano resonance.

Ultra-high sensitivity weak magnetic field detecting magnetic fluid surface plasmon resonance sensor based on a single-hole fiber

An ultra-high sensitivity weak magnetic field detecting magnetic fluid surface plasmon resonance (SPR) sensor based on a single-hole fiber (SHF) is proposed for detecting weak magnetic fields. The sensor is constructed with a single-hole fiber in which an exclusive air hole in the cladding is embedded with a metal wire and filled with a magnetic fluid (MF) to enhance the magnetic field sensitivity. The effects of the structural parameters, embedded metals, and refractive index difference between the core and cladding on the magnetic field sensitivity and peak loss are investigated and optimized. The sensitivity, resolution, figure of merit (FOM), and other characteristics of the sensor are analyzed systematically. The numerical results reveal a maximum magnetic field sensitivity of 451,000 pm/mT and FOM of 15.03 mT-1. The ultra-high magnetic field sensitivity renders the sensor capable of detecting weak magnetic fields at the pT level for the first time, in addition to a detection range from 3.5 mT to 17 mT. The SHF-SPR magnetic field sensor featuring high accuracy, simple structure, and ease of filling has immense potential in applications such as mineral resource exploration as well as geological and environmental assessment.

Cold and ultra-cold chain integrity monitoring via embedded resonant sensor indicators

An increasing number of products require transport at cold and ultra-cold temperatures, < 5 and −60°C respectively. Time-temperature indicators (TTIs) are used to monitor the integrity of the cold chain, however, they are frequently based on colorimetric changes that can be inaccurate for quantification and not possible to read through closed shipment materials. Here, TTIs were prototyped using microfluidic channels containing fluids (oils) that are tuned to melt above target temperatures. By coupling these TTIs to resonant sensors, the time-temperature information can be transmitted wirelessly and quantitatively by observing shifts in resonant frequency. Multiplexed TTIs containing fluids that melt at 9, 13.5, and 19.5°C are demonstrated. When coupled to the resonant sensor, the fluid flows as the temperature increases incrementally and generates a frequency shift of 3.5, 4.5, and 6 MHz at each threshold. TTI for ultra-cold environments were also designed using microfluidic channels with melt responsive fluids (ethanol). The resonant sensor coupled TTI was placed in a Styrofoam container containing dry ice, and over 1 MHz frequency shift is observed when read external to the container as the dry ice evaporates and the temperature exceeds −35°C. This augurs potential uses in inexpensive monitoring of food and pharmaceutical shipments that must remain cold for adequate quality.

A polarization independent highly sensitive metasurface-based biosensor for lab-on-chip applications

Metasurface-based sensors have emerged as an innovative technology in biosensing, offering enhanced sensitivity and versatility across a wide range of applications. In this study, we have proposed an asymmetric double T-shaped metasurface-based novel lab-on-chip and polarization-independent biosensor. Utilizing plasmonic metasurfaces for enhanced light-biomolecule interaction through near-field confinement effects, they enable streamlined processes, repeatability and reliability. Unlike surface plasmon resonance (SPR) sensors, metasurface-based sensors provide a comprehensive evaluation of plasmon parameters, significantly enhancing their analytical capabilities, which demonstrate exceptional stability, ensuring consistent and reliable results over time. The recorded sensitivity of the sensor is 1289.8 nm/RIU with a resolution of 7.753×10−7 RIU, which is capable of detecting minuscule changes in the refractive index of biomarkers. Our proposed novel sensor offers chemically stable and oxidization-free biosensing while ensuring rapid and selective diagnosis.

Replicating Spectral Baseline for Unambiguous Frequency Locking in Resonant Sensors.

Electrothermal piezoresistive resonant cantilever sensors have been fabricated with embedded actuating (heating resistor) and sensing (piezo resistors) parts, with the latter configured in a Wheatstone bridge circuit. Due to the close spacing between these two elements, a direct thermal parasitic effect on the resonant sensor during the actuating-sensing process leads to asymmetric amplitude and reversing phase spectral responses. Such a condition affects the precise determination of the cantilever's resonant frequency, f0. Moreover, in the context of phase-locked loop-based (PLL) resonance tracking, a reversing phase spectral response hinders the resonance locking due to its ambiguity. In this work, a replica of the baseline spectral was applied to remove the thermal parasitic effect on the resonance spectra of the cantilever sensor, and its capability was simulated through mathematical analysis. This replica spectral was subtracted from the parasitized spectral using a particular calculation, resulting in optimized spectral responses. An assessment using cigarette smoke particles performed a desired spectral shifting into symmetrical amplitude shapes and monotonic phase transitions, subsequently allowing for real-time PLL-based frequency tracking.

Enhancing Sensitivity of Double-Walled Carbon Nanotubes with Longitudinal Magnetic Field

In this study, the behavior of double-walled carbon nanotubes (DWCNTs) used as mass sensors is explored under various boundary conditions; particular attention is paid to the crucial topic of resonant nanomechanical mass sensors. In the presented approach, nanotubes are subjected to a distributed transverse magnetic force and supported by an elastic foundation. The impacts of the longitudinal magnetic field, elastic medium, and diverse physical parameters on the responsiveness of the sensors are assessed. Using the energy method, governing equations are formulated to determine the frequency shifts of the mass nanosensors. Our findings reveal significant variations in the frequency shifts due to a longitudinal magnetic field, which depends on the applied boundary conditions. This research holds significance in the design of resonant nanomechanical mass sensors and provides valuable insights into the interplay of factors affecting their performance. Through exploring the intricate dynamics of DWCNTs used as mass sensors and thus contributing to the broader understanding of nanoscale systems, the implications for advancements in sensor design are offered and applications are introduced.

Optimizing PCF-SPR sensor design through Taguchi approach, machine learning, and genetic algorithms

Designing Photonic Crystal Fibers incorporating the Surface Plasmon Resonance Phenomenon (PCF-SPR) has led to numerous interesting applications. This investigation presents an exceptionally responsive surface plasmon resonance sensor, seamlessly integrated into a dual-core photonic crystal fiber, specifically designed for low refractive index (RI) detection. The integration of a plasmonic material, namely silver (Ag), externally deposited on the fiber structure, facilitates real-time monitoring of variations in the refractive index of the surrounding medium. To ensure long-term functionality and prevent oxidation, a thin layer of titanium dioxide (TiO2) covers the silver coating. To optimize the sensor, five key design parameters, including pitch, air hole diameter, and silver thickness, are fine-tuned using the Taguchi L8(25) orthogonal array. The optimal results obtained present spectral and amplitude sensitivities that reach remarkable values of 10,000 nm/RIU and 235,882 RIU-1, respectively. In addition, Artificial Neural Network (ANN) optimization techniques, specifically Multi-Layer Perceptron (MLP) and Particle Swarm Optimization (PSO), are used to predict a critical optical property of the sensor confinement loss (αloss). These predictions are derived from the same input structure parameters that are present in the full L32(25) design experiment. A genetic algorithm (GA) is then applied for optimization with the goal of maximizing the confinement loss. Our results highlight the effectiveness of training PSO artificial neural networks and demonstrate their ability to quickly and accurately predict results for unknown geometric dimensions, demonstrating their significant potential in this innovative context. The proposed sensor design can be used for various applications including pharmaceutical inspection and detection of low refractive index analytes.

Chemical additive effect on asphaltenes destabilization and deposition studied using quartz crystal resonator (QCR) sensor: From atmospheric pressure titration to isothermal depressurization of non-diluted crude oil

In this study, the destabilization of asphaltenes in a crude oil sample was analyzed under various pressure conditions using a fully immersed Quartz Crystal Resonator (QCR) sensor. Firstly, oil samples with and without a chemical additive were tested at atmospheric pressure through titration with different liquid n-alkanes (C7, C9, and C12) as antisolvents. Then, high-pressure experiments (HP) were conducted on a recombined crude oil + gas system, involving constant mass expansions from 1000 bar to the saturation pressure point at various fixed temperatures. From these high-pressure experiments, the phase diagrams, including the asphaltene pressure envelope (APE), were constructed and compared for the recombined oil with and without the chemical additive in both P vs T and P vs composition diagrams. The results regarding the impact of the chemical additive under HP conditions were compared with those obtained under atmospheric pressure conditions. The comparison shows an strong agreement between the two sets of experiments, confirming that the test conducted to evaluate the effectiveness of asphaltene inhibitors can be extrapolated to high-pressure applications.

A silicon resonant pressure sensor based on thermal stresses matched structures

This paper introduced a silicon resonant pressure sensor based on thermal stress-matched structures to extend the operating temperature range. The sensor designed this time consists of an SOI wafer with a pressure-sensitive diaphragm for pressure sensing and two integrated resonators, a silicon wafer for vacuum packaging, and a glass wafer for additional stress isolation. The multilayer structures were bonded together to form a thermal stress-matched part to address the problem of temperature inflection points of conventional resonant pressure sensors within broad temperature zones. Finite element analyses optimized the sensor’s pressure- and temperature-sensitive characteristics. Micromachining based on eutectic and anodic bonding to fabricate sensor chips. Characterization results indicated the developed pressure sensor can work stably in a wide temperature range of -55∼125°C and has excellent fitting accuracy exceeding ±0.01% FS., which showed a better performance than previously reported counterparts.