High-sensitivity Measurements Research Articles

Novel Series Elastic Actuator towards High Torque Capacity with High Sensitive Torque Measurement

Novel Series Elastic Actuator towards High Torque Capacity with High Sensitive Torque Measurement

A High-Sensitivity Magnetic Moment Measurement System for Large Samples Based on a Single-Axis Atomic Magnetometer

A High-Sensitivity Magnetic Moment Measurement System for Large Samples Based on a Single-Axis Atomic Magnetometer

Angularly Cascaded Long-Period Fiber Grating for Curvature and Temperature Detection.

A high-sensitivity curvature sensor with dual-parameter measurement ability based on angularly cascaded long-period fiber grating (AC-LPFG) is proposed and experimentally demonstrated, which consists of two titled LPFGs (TLPFGs) with different tilt angles and the same grating period. AC-LPFG was fabricated by using a deep ultraviolet laser and an amplitude-mask in our laboratory. The experimental results show that simultaneous measurement of curvature and temperature can be achieved by monitoring the wavelengths of two resonant peaks for different TLPFGs. The two peaks show opposite shifts with increasing curvature and has a maximum curvature sensitivity of 16.392 nm/m-1. With the advantages of low cost, high sensitivity, and dual-parameter measurements, our sensor has more potential for engineering applications.

High-sensitivity and directional-identification fiber magnetic field sensor via polarimetric fiber ring laser with a fiber Faraday rotator

A highly sensitive fiber magnetic field sensor with directional identification utilizing multi-longitudinal-mode fiber ring laser (FRL) based on polarization-mode beat frequency (PMBF) is experimentally demonstrated. A bismuth-doped iron garnet (BIG), as a kind of fiber Faraday rotator, is embedded in the FRL and serves as a fiber magnetic field probe, whose birefringence shows strong dependence on the external magnetic field due to magneto-optical Faraday effect, leading to the frequency drift of PMBF. Thus, the external magnetic field can be characterized by monitoring the change in a certain PMBF. Additionally, the drift direction of the tracked PMBF is closely related to the applied magnetic field direction, which is attributed to the non-reciprocity of Faraday magneto-optical rotation. Therefore, it shows the good ability to distinguish the applied forward (positive) and reverse (negative) magnetic field. The experimental results reveal that the tracked PMBF signal near 100 MHz has opposite frequency drift signs in the forward (positive) range of 0–20 mT and reverse (negative) range of 0 - −20 mT, which can be used to identify the axial orientation of the applied magnetic field. Additionally, it shows the maximum magnetic field sensitivities of −100.76 and −105.73 kHz/mT in the positive and negative magnetic field ranges, respectively. The designed device makes full use of the advantages of the fiber laser that rapidly demodulates the magnetic field with the help of high-speed digital processing technology, as well as fast response, high integration and low cost of fiber Faraday rotator, offering potentials in high-sensitivity magnetic field measurement in a confined space.

Analysis on bimodal complex permeability spectrum of a noise suppression sheet and single constituent flakes

In recent years, highly integrated active components inside small mobile communication devices have led to serious electromagnetic interference problems. The countermeasure to this problem is covering a noise source with a noise suppression sheet (NSS) which is composed of ferromagnetic flakes and polymers. The NSS absorbs effectively electromagnetic waves due to a large imaginary part of relative permeability μr″ at the specific frequency region. This function is attributed to the bimodal μr″ spectrum of NSS, but its physical origin has not been revealed so far. In this study, the bimodal μr″ spectrum of NSS has been analyzed and its physical mechanism has been discussed. The μr″ spectrum of a constituent single magnetic flake was measured by using a newly developed high-sensitivity permeability measurement system, which showed a bimodal spectrum quite similar to that of NSS. This fact indicates that the physical origin of the bimodal μr″ spectrum is attributed to the magnetization dynamics of each single constituent flake. After measuring the μr″ spectra of single flakes with various materials, such as Fe, Fe-Al, Fe-Co-V, and Fe-Si-Al alloys, these bimodal μr″ spectra were quantitatively explained by the magnetization dynamics of the flux closure states inside the flake. The magnetic domain structure of a single flake was observed by a micro-beam X-ray magnetic circular dichroism microscopy. The result confirmed that the segmented magnetic domains form the local flux closure states inside the flake.

A fibre Bragg grating accelerometer with temperature insensitivity for cable force monitoring of FAST

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) currently holds the distinction of being the largest single-aperture telescope worldwide. To ensure its secure functioning, it is crucial to monitor the cable force on its active reflecting surface cable network structure. In this paper, a fibre Bragg grating (FBG) accelerometer is developed to acquire low-frequency vibration signals of the cables. The sensor’s cantilever beam structure enables high sensitivity measurement of low-frequency signals, while the symmetrical double fibre grating structure effectively eliminates the impact of temperature. The sensor’s specific limiting structure ensures its survival during transportation and installation. A series of laboratory tests have been performed, and they demonstrate the excellent measurement performance, temperature insensitivity and practical usefulness of the accelerometer. Ninety FBG accelerometers are successfully installed on the site of the FAST project, where they are precisely measuring and documenting the magnitude of force exerted on the edge cables.

2-Dimensional Materials for Performance Enhancement of Surface Plasmon Resonance Biosensor: Review Paper

Surface plasmon resonance (SPR)--based biosensors compete and excel among optical biosensors because of exceptional features such as high sensitivity, label-free, and real-time measurement, allowing the observation of molecular binding kinetics. In SPR biosensors and other biosensor techniques, surface functionalization and bioreceptor attachment are effective strategies to improve sensor performance. The application of an appropriate immobilization matrix for the bioreceptor is an essential step in maximizing the absorption of the bioreceptor on the sensor surface, thereby improving a specific target-sensor interaction. Furthermore, the materials should provide excellent optical properties to enhance the response signal. The high surface-to-volume ratio and high optical absorption of 2D materials qualify these requirements, thus promising advancements for SPR biosensors. This article reviews the recent SPR biosensor study with the use of the 2D materials family to improve the sensor performance, including graphene, transition metal dichalcogenides (TMDCs), MXene, black phosphorus (BP), perovskite, and boron nitride (BN). The materials properties and enhancement mechanisms of different 2D materials are discussed comprehensively. This review was expected to provide a future perspective and design approach for 2D materials-based SPR biosensors.

An in-fiber sensor for simultaneous measurement of cholesterol concentration and temperature based on SPR and MMI

In this paper, we design an in-fiber two-parameter sensor with multimode fiber (MMF)-Au film coated hollow fiber (HCF)-MMF structure, which can simultaneously excite Surface Plasmon Resonance (SPR) effect and Multimode Interference (MMI) effect. A composite material of Au nanoparticles/β-cyclodextrin (AuNPs/β-CD) is deposited on the surface of the Au film coated HCF to realize highly-sensitive measurement of cholesterol concentration. Here, the AuNPs can not only enhance the measurement sensitivity of the SPR sensor, but also increase the numbers of combination sites of β-CD and cholesterol. Then, to solve the cross-sensitivity problem between temperature and cholesterol, the glycerin is selected as a temperature-sensitive material to fill into the inner channel of the HCF, making the MMI sensor sensitive to temperature, and finally realizing the simultaneous measurement of cholesterol concentration and temperature. The experimental results demonstrate that the wavelength shift of the SPR and the MMI are 12.7 nm and 7.9 nm, respectively, when the cholesterol concentration changes from 0 to 500 nM. The temperature sensitivity of the SPR and the MMI are −0.9 nm/°C and 2.64 nm/°C, respectively, in the temperature range of 30°C–46 °C. In addition, the sensor shows good recognition ability of cholesterol molecules in serum environment, with good stability, selectivity and repeatability, and has broad application prospects in the biomedical field.

Development and characterization of a highly sensitive magnetic electronic skin for intelligent manipulators

A magnetic electronic skin (e-skin) with high sensitivity, flexibility, and wide force measurement range was designed. The e-skin includes a top magnetic film layer, a middle polydimethylsiloxane (PDMS) layer and a bottom tunneling magnetoresistive sensor layer. The magnetic film layer is composed of neodymium-iron-boron particles (Nd2Fe14B) and PDMS. A test platform was established. The test results showed that the e-skin could measure forces in the range of 0.05–20 N, with a static sensitivity of 287 mV/N within 0–1 N, followed by a gradual decrease in sensitivity with an increase in static force. The resolution of the electronic skin was 0.05 N, and the change in sensitivity under dynamic force was less than 3.17 %. The response time and recovery time were 41 ms and 40 ms, respectively. This study provides a foundation for further research and development of advanced electronic skins for use in a variety of flexible electronic applications.

A neural network filter based high-sensitive MIR CO2 sensor

A low-power consumption, small-size and high measurement sensitivity mid-infrared (MIR) carbon dioxide (CO2) sensor was developed based on wavelength modulation spectroscopy (WMS) technology, utilizing a mid-infrared distributed feedback interband cascade laser (DFB-ICL) operating around 2682 nm. The sensor incorporated two key components, a home-made multi-pass gas cell with base length of 10 cm achieving 1.5 m optical path and a highly integrated FPGA board, which were used to reduce the size of the sensor. A novel second harmonic-neural network filter (SH-NNF) was also proposed and implemented in this sensor. The sensor’s performance was evaluated through a 20 mins continuous experiment using calibrated gas with 500 ppm concentration. The results, before and after SH-NNF, demonstrated an improvement in sensitivity and detection precision from 1.68 ppm (1 σ) to 1.17 ppm and from 2.14 ppm to 1.45 ppm, respectively. The optimum limit of detection of 0.392 ppm with integration time of 218 s was obtained. The ppm detection and compact characteristics of the developed MIR sensor show its potential for detecting CO2 in the ambient air.

Microscale, Electrochemical, Aptamer-Based Sensors for Enhanced Small-Molecule Detection at Millisecond Time Scales.

Microscale electrodes offer the advantages of increased mass transport rates, high sensitivity, and rapid measurement capabilities. Fabricating electrochemical aptamer-based (E-AB) sensors on these electrode platforms opens new applications to chemical and biological sensing but has remained challenging due to low signal-to-noise ratios and monolayer instability. In this article, we report the development and characterization of E-AB sensors on a gold microelectrode platform (∼500 nm radius). To overcome the small current response, we modified the electrodes by growing nanostructures via electrodeposition. We interrogated the sensors with two different electroanalytical techniques, square wave voltammetry (SWV) and intermittent pulse voltammetry (IPA), to measure the representative response of an ATP sensor and determine aptamer-target binding and dissociation time scales. We find robust and stable sensor performance with an increased response rate over sensors fabricated on macroscale electrodes. These results demonstrate that sensors developed on this microelectrode platform can be employed for enhanced spatiotemporal resolution measurements in chemical and biological environments.

Machine learning-based global air quality index development using remote sensing and ground-based stations

Air pollution refers to the presence of hazardous substances in the air that has adverse effects on health, causing millions premature deaths annually. Ground-based stations can provide accurate measurements for monitoring air pollution. However, the spatial coverage of air pollution measurements is limited by the number of measurement instruments available in specific hotspot areas. Satellite remote sensing can reduce spatial uncertainty; however, the measurement results are mostly limited to the upper atmosphere with high measurement sensitivity. To better represent surface conditions, this study aims to model the Air Quality Index for pollutants CO, NO2, SO2, PM2.5, and PM10 in the global region using remotely sensed data. To support this study, 425 data points from air pollution stations distributed globally are combined using Machine Learning Linear Regression methods. Furthermore, socioeconomic and environmental data are combined with air pollution satellite to form Multiple models. According to the results of this study, the Multiple Models are more accurate than the single models, showing that the addition of socioeconomic and environmental data can enhance accuracy. The results of this study are expected to help regions without air pollution monitoring stations to estimate the air quality index using satellite data, in turn, preventing air pollution disasters.

Design and analysis of surface-plasmon-resonance-based dual-cladding micro-structured fiber temperature and refractive index sensor

Combining the surface plasmon resonance(SPR) effect and the characteristics of dual-cladding micro-structured fiber(DC-MF), this study presents the design and analysis of a temperature and refractive index sensor. The performance of the sensor is analyzed by using the full-vector finite element method, and the structure parameters of the DC-MF and the thickness of the plasmonic material (ITO film), is optimized to achieve high sensitivity measurements of temperature and refractive index. Theoretical analysis results indicate that its maximal temperature and refractive index sensitivity can reach to 25.4 nm/°C and 46559.8 nm/RIU in −40 °C to −40 °C. Its average temperature and refractive index sensitivity is 22.53 nm/°C and 38292.3 nm/RIU in the temperature range from −40 °C to 0 °C, and the value is 7.03 nm/°C and 12591.7 nm/RIU in the temperature range from 0 °C to 40 °C. Besides, its operating wavelength shifts toward a long wavelength region (about 1.05 μm–2.25 μm) as the refractive index of analyte increases from 1.424 to 1.471.

High Sensitivity Singlet Oxygen Luminescence Sensor Using Computational Spectroscopy and Solid-State Detector.

This paper presents a technique for high sensitivity measurement of singlet oxygen luminescence generated during photodynamic therapy (PDT) and ultraviolet (UV) irradiation on skin. The high measurement sensitivity is achieved by using a computational spectroscopy (CS) approach that provides improved photon detection efficiency compared to spectral filtering methodology. A solid-state InGaAs photodiode is used as the CS detector, which significantly reduces system cost and improves robustness compared to photomultiplier tubes. The spectral resolution enables high-accuracy determination and subtraction of photosensitizer fluorescence baseline without the need for time-gating. This allows for high sensitivity detection of singlet oxygen luminescence emission generated by continuous wave light sources, such as solar simulator sources and those commonly used in PDT clinics. The value of the technology is demonstrated during in vivo and ex vivo experiments that show the correlation of measured singlet oxygen with PDT treatment efficacy and the illumination intensity on the skin. These results demonstrate the potential use of the technology as a dosimeter to guide PDT treatment and as an analytical tool supporting the development of improved sunscreen products for skin cancer prevention.

Self-calibrated defocused speckle imaging for remote surface motion measurements

Defocused Speckle Imaging (DSI) is a non-contact optical method that can measure multiaxial object motions at microscopic sensitivity using a simple and mechanically robust optical setup. The object surface is illuminated by a laser beam, and the scattered interference speckle pattern is tracked with a defocused camera. DSI measurement sensitivity increases with distance, and the sensitivity can be tuned by simple camera defocus adjustment. These characteristics make DSI an attractive choice for tracking remote objects in field conditions. However, the use of DSI for practical measurements is limited because the speckle signals due to linear and rotational surface motions mix together, and because the instrument calibration requires accurate object range and surface orientation parameters.To address these issues, the work described here combines two recently presented concepts: 1) a defocused camera pair, and 2) a diffraction-based self-calibration principle. The proposed approach was demonstrated by a series of self-calibrated multiaxial motion measurements performed at an extended (30.7-m) distance. The studied motions included in-plane displacements and out-of-plane rotations (tilts), whereas out-of-plane displacements and in-plane rotations were excluded. The experiments showed DSI's capability for high tilt sensitivity down to 0.0006°, standalone remote angle measurements, and suitability for retroreflective surfaces. The diffraction-based self-calibration approach could monitor sampling distances at a 6.4 % accuracy and the relative surface angles of 2.5–7.4° at a 0.2° accuracy. The defocused camera pair tracked microscopic in-plane displacements (400 µm) and very fine out-of-plane tilts (0.003°) at a high accuracy, with a maximum uncertainty of 6.0 %.The proposed DSI approach is particularly suited for monitoring large objects and for operating in hazardous environments. The findings pave a way for interesting new applications, like high-range remote angle measurements, high-sensitivity straightness measurements, and 3D-positioning utilizing retroreflective markers that already exist in the built infrastructure.

Polarization control and enhanced magnetic field sensitivity utilizing surface plasmon polaritons-assisted dual-V-type four-level system

We propose a kind of surface plasmon polaritons (SPPs)-assisted dual-V-type four-level composite system used for high-sensitivity weak magnetic field measurement. The SPPs are excited by a D-shaped photonic crystal fiber (PCF) deposited with gold nanowires, and are interacted with the above quantum emitter from the rubidium atomic vapor. In the presence of the external magnetic field, Faraday rotation symmetry is broken due to Zeeman effect, resulting in the polarization plane rotation when a linearly polarized probe field goes through the above quantum emitter. With the help of the coupled field and SPPs, Faraday magneto-optical rotation (MOR) are effectively regulated. The Rabi frequency of the coupled field (Ω c ), quantum interference degree (q), and phase difference (φ) between the applied fields show strong dependence on the MOR angle and magnetic field measurement sensitivity. The simulated results reveal that the maximum MOR angle and magnetic field sensitivity both damp with Ω c expanding and q reducing. The maximum dichroism-independent MOR angle of 89.97° is realized for φ = 0° (180°), and the magnetic field sensitivity of 10.88°/Oe is obtained in the sweeping range of −8.88–8.88 Oe for q = 0.99, being 2.66°/Oe higher than that in the absence of SPPs (q = 0). Most importantly, the output probe field with different polarization forms can be realized by adjusting the φ value. Hence, the proposed device exhibits the potential in the fields of weak magnetic field measurement and polarization control.

High-sensitivity optical fiber SPR sensor with cascaded biconical fiber and hetero-core structure for simultaneous measurement of seawater salinity and temperature

A novel dual-channel optical fiber surface plasmon resonance (SPR) sensor, which achieves high-sensitivity simultaneous measurement of seawater salinity and temperature, was designed and verified. The hetero-core structure based on no-core fiber (NCF) with 40 nm thick Au film and polydimethylsiloxane (PDMS) overlaying was utilized to excite the SPR effect and serve as the temperature sensing channel. In order to effectively separate from the temperature SPR dip, a silver/gold bimetallic film was deposited on the surface of the biconical fiber with a grinding angle of 14° to construct the salinity channel cascaded with the temperature channel, where the metal thickness was determined as Ag/Au: 30 nm/10 nm. The simulation and experimental results showed that the bimetallic film used in this article can significantly improve the figure of merit (FOM) of the sensor compared with the optical fiber SPR sensor deposited with a single kind of metal film. In addition, further experimental results on salinity and temperature indicated that the proposed sensor had a salinity sensitivity of 0.73 nm/‰ and a temperature sensitivity of −2.43 nm/℃, and demonstrated the advantages of ease of manufacturing, acceptable repeatability, and good stability. Therefore, the proposed dual-channel optical fiber SPR sensor has high research value and application prospects in the field of ocean measurement.

Minimum Detection Concentration of Hydrogen in Air Depending on Substrate Type and Design of the 3ω Sensor.

Hydrogen has emerged as a promising carbon-neutral fuel source, spurring research and development efforts to facilitate its widespread adoption. However, the safe handling of hydrogen requires precise leak detection sensors due to its low activation energy and explosive potential. Various detection methods exist, with thermal conductivity measurement being a prominent technique for quantifying hydrogen concentrations. However, challenges remain in achieving high measurement sensitivity at low hydrogen concentrations below 1% for thermal-conductivity-based hydrogen sensors. Recent research explores the 3ω method's application for measuring hydrogen concentrations in ambient air, offering high spatial and temporal resolutions. This study aims to enhance hydrogen leak detection sensitivity using the 3ω method by conducting thermal analyses on sensor design variables. Factors including substrate material, type, and sensor geometry significantly impact the measurement sensitivity. Comparative evaluations consider the minimum detectable hydrogen concentration while accounting for the uncertainty of the 3ω signal. The proposed suspended-type 3ω sensor is capable of detecting hydrogen leaks in ambient air and provides real-time measurements that are ideal for monitoring hydrogen diffusion. This research serves to bridge the gap between precision and real-time monitoring of hydrogen leak detection, promising significant advancements in the related safety applications.

Synthesis, characterization, and application of a polymeric capillary fiber derived from methacrylic acid in the determination of cocaine in blood by FSI-MS

The development of probes/substrates that enable in-situ and in-natura biological analysis, capable of adsorbing analytes and enabling effective ionization, can be an alternative for detecting illicit drugs present in these matrices. Particularly, fiber spray ionization mass spectrometry (FSI-MS) shows promise because it enables straightforward and direct analyses without prior sample treatment or processing. In this study, a polymeric capillary fiber was developed and applied as a probe/substrate in FSI-MS experiments for the sampling and ionization of blood samples. The fiber was directly immersed in a solution of whole blood doped with cocaine (COC) and deuterated cocaine (COC-d3) to optimize the experimental conditions. The developed analytical approach was evaluated using whole blood samples taken from individuals suspected of drug abuse. Additionally, paper spray ionization mass spectrometry (PSI-MS) analyses were performed for comparison with the FSI-MS technique. The FSI analysis in positive mode, FSI(+), was effective in detecting COC and its metabolites with high sensitivity and accurate mass measurements. Evaluation of the whole blood sample collected from a suspected user revealed higher sensitivity for COC detection by FSI than by PSI. The quantification of COC in whole blood by FSI(+) showed detection and quantification limits of 32.0 and 106.7 ng mL−1, respectively. In addition, linearity was observed, with a coefficient of determination above 0.99 and a relative standard deviation ranging from 0.47 % to 8.58 %.

In-plane ESPI with unlimited angle of view for multi-object rotation angle determination

The in-plane electronic speckle pattern interferometry (ESPI), implemented in a Michelson stellar interferometer-like configuration, offers high sensitivity and dynamic measurement. However, its limited angle of view (AOV) remains a major challenge for the rotation angle determination of multiple objects. In this Letter, we analyze the main factors that influence the AOV of the in-plane ESPI and propose an “image transmitting” approach to enlarge the AOV. With the aid of a folded dual-telescope imaging system, we develop an AOV-unlimited interferometer that can determine multi-object rotation angles in real time. The practicability of the interferometer is demonstrated by the application in real-time measuring of the rotation angles of the disks within a 2D granular system.