Sensors and Actuators A-physical最新文献

Magnetoelectric (ME) composites are promising for the development of high-performance magnetometers due to their high sensitivity, low cost, low power consumption, and small size. Enhancing the ME coefficient while reducing the background noise is an effective method to improve the performance of ME sensors, which remains challenging. In this work, we propose a method to reduce the equivalent magnetic noise by optimizing the electrode design and the magnetic annealing process in magnetoelectric quartz/Metglas composites. Compared with the non-optimized ME composites, the ME coefficient increases by 1.38 times while the background noise decreases by about 0.78 times, resulting in a LoD of 10 fT at resonance. Due to the high ME coefficient and low background noise, the equivalent magnetic noise from 20 kHz to 50 kHz was less than 6.10 pT/Hz^1/2. The results show that proper annealing treatment of Metglas is beneficial for improving the soft magnetic properties. Meanwhile, the hollow electrode of quartz can reduce the equivalent capacitance and enhance the quality factor of the piezoelectric layer. This work demonstrates a feasible way to enhance the performance of ME magnetic field sensors.

This work aims to investigate the detection performance of WS₂ and its doped gas sensitive materials for carbon monoxide (CO), one of the most important characteristic gases of partial discharge in air switchgear.Its accurate monitoring can be an effective evaluation of the operating condition of air switchgear. Three gas-sensitive materials were synthesized using the hydrothermal method: WS₂, Pt-WS₂, and Au-WS₂. The materials were characterized through XRD, SEM, and XPS, followed by an evaluation of their sensing performance for CO gas. The findings revealed that the gas sensitivity of WS₂ was significantly enhanced through doping with Pt and Au. At a CO concentration of 10 ppm, the response sensitivity of the Pt-WS₂ sensor reached 4.03, while that of the Au-WS₂ sensor was measured at 2.68—both representing an increase by a factor of 3.52 compared to intrinsic WS₂ sensors. Moreover, the response recovery time for the Au-WS₂ sensor was found to be 20–30 s faster than that observed in Pt-WS₂ sensors. The mechanisms underlying the enhancement in CO adsorption on WS₂ due to Pt and Au doping were investigated based on density functional theory calculations encompassing band structure analysis, density of states assessment, adsorption distance measurement, and adsorption energy evaluation. This study posits that both Pt-WS₂ and Au-WS₂ can be used for the detection of partial discharge gas CO in air switchgear.

We report a non-destructive and in-situ measurement technique to infer the internal temperature inside a sealed cell of an atomic magnetometer, based on steady-state linewidth analysis. This approach exploits the relationship between the alkali vapor density and the steady-state linewidth of the magnetometer in the presence of an applied DC magnetic field, particularly when the spin polarization of the alkali metal is significantly low ($P\ll 1$). The atomic density inside the cell is a univariate nonlinear function of the cell temperature, enabling us to establish a model linking the magnetometer’s steady-state linewidth to the internal temperature of the cell. To validate the accuracy and feasibility of this method, we conducted a series of experiments over a wide temperature range, from 140 °C to 190 °C. Using the magnetometer’s steady-state linewidth as a key parameter, we successfully measured the actual temperature inside the cell. The test results were corrected to ensure precision and reliability, and comprehensive evaluations of measurement uncertainty were performed to quantify the confidence level in the temperature measurements. This novel determination method marks a significant advancement in atomic magnetometer temperature measurement, offering real-time and on-site monitoring capabilities within sealed cells.

In the field of health monitoring and electronic skin, flexible wearable sensors have attracted considerable research interest. However, preparing a flexible multifunctional sensor that simultaneously possesses a rapid response time, stability, reliability, high breathability, as well as high sensitivity remains a significant challenge. Herein, a flexible pressure-humidity dual-mode sensor based on nonwoven fabrics is developed in this study, using hydroentangled nonwoven fabric with graphene oxide/carbon nanotube composite as the sensing layer and polyester plain nonwoven fabric with carbon nanotube printed interdigitated electrodes as the electrode layer. The sensor exhibits high permeability (649.2 mm/s), high sensitivity (2.72 kPa⁻¹), wide sensing range (0–220 kPa), fast response/recovery time (24.4 /73.3 ms), and low detection limit (2.79 Pa). In addition, the sensor exhibits excellent cyclic stability (15,000 cycles) and can detect both weak body movements (pulses, swallowing) as well as large deformational movements (joint movements). Furthermore, the sensing layer of the sensor responds quickly to different humidity levels, which can be used to monitor humidity in real time, and human breathing and speech can be monitored by placing it inside a mask. This high-performance flexible pressure-humidity dual-mode sensor shows promising potential for applications in health monitoring and respiratory monitoring.

Hierarchically oriented plasmonic nanostructures have attracted an advanced molecular sensing platform for multifaceted applications. In the present work, we have attempted to fabricate ultrasensitive and cost-effective pyramidal/nanowire hetero arrays, hosted with silver nanoparticles for the effective surface-enhanced Raman spectroscopy (SERS) assisted detection of toxic water contaminants. Three-dimensionally oriented pyramidal/nanowire hetero arrays with enhanced surface area were fabricated by combining wet etching and metal-assisted chemical etching techniques. The regulation of structural features was achieved by controlling the process parameters during fabrication. Particularly, the evolution of morphological properties of the hybrid sensor was investigated in terms of nanowire aspect ratio and further analyzed in terms of SERS properties. The hetero arrays exhibited significant enhancement in Raman signal for sensing organic pollutants. Moreover, these hetero arrays with a nanowire length of ∼1 µm exhibited the highest signal enhancement. Further, the excellent reproducibility and reusability characteristics were also demonstrated for the fabricated sensors. Different cationic and anionic organic pollutants were employed for efficacy studies which showed detection limits ranging from femtomolar to picomolar levels. Finally, the real-time sensing of organic contaminants such as aniline was also investigated from seawater with an estimated enhancement factor of 8 × 10⁸, indicating that as-fabricated hetero arrays can perform as outstanding SERS sensors for environmental remediation applications.

An important aspect of controlling the properties of liquids relates to their use in modern engines powered by composite materials. In this context, controlling the properties of industrial fluids containing micro- and nanoscale particles is essential. Understanding the temperature-dependent behavior of fluid density and elasticity is crucial for proper engine operation. Seven physical parameters of pure paraffin oil, paraffin oil with varying concentrations of activated coal nanoparticles or sorbitane monooleate (SPAN 80) were simultaneously determined using only BAW time delay measurement in the single experimental run. This technique relies on propagating LBAW through the test fluid and measuring the time delay and amplitude of these waves at different temperatures. By calculating temperature coefficients for velocity, density, time delay, and expansion using well-established formulas the physical properties of fluids under study were determined. The frequency of the LBAW used in the experiment was 13 MHz. The length of the liquid sample in the propagation direction of LBAW was ∼ 5 mm. The experiments were carried out within a temperature range of −20 °C to +90 °C. The volume of the test sample was around 1 milliliter. The comparison of the physical properties of different suspensions under these conditions allows us to demonstrate the dependence of the measured properties on the type and composition of the medium tested.

The different phases of α-, β-, and γ-graphyne, which are new types of two-dimensional carbon allotropes, hold promise as potential candidates for designing substrate discs in piezoelectric nanogenerators. Accurate modeling of the bending rigidity and stretching properties as well as resonance frequencies of these materials is crucial for engineering applications like nano-resonator and nanogenerator systems. This step is imperative in designing and advancing future applications involving these structures. This study aims to create a hybrid atomistic-continuum model for modeling graphyne monolayers used as substrate discs in nanogenerators. The model integrates the benefits of both atomistic and continuum approaches. Based on the results, α-graphyne is the least mechanically stable, while γ-graphyne is the most stable. However, in terms of vibration frequency, α-graphyne has the highest frequency while γ-graphyne has the lowest. Therefore, β-graphyne, with moderate stability and resonance frequency, is recommended as the ideal choice for the substrate disc in piezoelectric nanogenerators. It can function within the Q-F frequency range (30–140 GHz) and induce deformation in the piezoelectric shim as well as generation voltage.

This work introduces an integrated fluxgate sensor fabricated using CMOS chip technology. The sensor uses a “racetrack” shape of the core. The material used for the core is VITROVAC 6025F, and the shape was laser-cut from 25 $\mu$m thick foil. The coils are solenoids fabricated using metal layers of the chip and bonding wires. Sensing and excitation coils have 60 and 40 turns respectively. TSMC D35 technology was used for fabrication. The size of the core is 8 mm $\times$ 1.75 mm. Dimensions of the chip are 8 mm $\times$ 2.7 mm (21.6 mm${}^2$).

The sensor was tested in open-loop operation using a sinewave excitation. Sensitivity increases with frequency up to 1.5 MHz, reaching 5000 V/T. This is a significantly higher value than what can be achieved using a flat pick-up coil (around 10 V/T). Fully saturating the core requires a 110 mA excitation current, leading to 300 mW power dissipation in the coil. The Core loss is 100 mW at 1 MHz excitation. The Noise at 1 Hz may be as low as $2nT/\sqrt{H}z$ depending on excitation signal parameters. The typical offset is below 1 $\mu$T.

A quasi-static multi-degree-of-freedom piezoelectric MEMS micromirror with large mirror plate and high fill factor based on AlScN is presented. It consists of two individual components, namely the mirror plate and the actuator. They are fabricated separately and vertically assembled together to form the final combination. In current case, a square mirror plate with side length of 5 mm is used. The actuator is designed into a gimbal-less structure, which involves a central connection platform with a mounting hole and four groups of piezoelectric actuators that are connected to the platform's corners via serpentine springs. This configuration provides multi-degree-of-freedom driving capabilities, allowing tip-tilt-piston mirror movement. The piezoelectric actuator is composed of three-stage cantilever-type actuation units that are connected in series, and they are intentionally arranged into S-shape so as to be completely hidden beneath the mirror plate. Moreover, the driving performance is further improved by optimizing the electrode coverage region on each actuation unit. As a result, not only large displacement but also nearly 100 % fill factor as well as high optical utilization efficiency can be achieved. From experimental results, the as-fabricated MEMS micromirror demonstrates static mechanical tilt angles of approximately ±2.2° about two orthogonal axes and piston vertical movement of ±54.9 μm within ±50 V_DC driving voltage range with excellent linearity. Given the large mirror size, high fill factor and multi-degree-of-freedom motion advantages, the proposed micromirror could be found application perspective in light field shaping, free space optical communication and projection lithography areas.

Understanding the mechanical and thermal properties of MoS₂ multilayers is of importance for applications ranging from nano-mechanical structures to high-performance flexible electronics. The conventional methods such as micro-Raman spectroscopy, are often constrained by factors like probing laser beam induced heating and substrate interactions. In the present work, we demonstrate a novel method to estimate the Young’s modulus, strain and thermal expansion co-efficient of MoS₂ multilayers using a bimaterial like micro-mechanical device made of MoS₂ and SiO₂. SiO₂ microcantilevers (MC) were fabricated using bulk micromachining technique and MoS₂ layers were grown on one side of the device by chemical vapor deposition method. Shift in resonance frequency due to the added MOS₂ layers on MCs was used to estimate the Young’s modulus of layered MoS₂. Similarly, growth induced curvature change of the bimaterial MCs was measured to estimate the interfacial stress between the MoS₂ multilayers and the substrate. From the measured temperature induced curvature changes, thermal expansion co-efficient of layered MoS₂ was estimated.