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An Ultrasensitive and Ultraselective Hydrogen Sensor Based on Defect-Dominated Electron Scattering in Pt Nanowire Arrays
摘要： The detection of hydrogen gas has attracted extensive attention due to its wide applications. Here, ultrathin Pt nanowires (3.5 nm) with abundant defects are fabricated by focused ion beam (FIB) for hydrogen detection. Different from the surface-dominated scattering in previous reports where the resistance of Pt decreases after hydrogenation, the Pt hydrogen sensor prepared by FIB is based on defect-dominated electron scattering owing to the abundant defects, i.e., the resistance is dominated by defect scattering, while H atoms will diffuse along the defects and thus enhance the electron scattering and resistance. Thanks to the small volume of H atoms (easy to diffuse along defects), the sensor is very sensitive and selective to hydrogen and exhibits fast response–recovery properties. Moreover, the sensitivity can be improved after the response–recovery loops, which may be ascribed to the generation of extra defects (further accelerating H atom diffusion). After response in pure H2 and recovery in air, the sensor has an ultralow limit of detection (for H2 in air) of 10 ppb. The results present a hydrogen sensor with superior sensitivity and selectivity, which would not only facilitate the development of metal hydrogen sensors, but also provide a feasible strategy for hydrogen detection.
关键词： platinum nanowires,hydrogen sensors,diffusion,defects,resistance
更新于2025-09-09 09:28:46
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A review of optical methods for continuous glucose monitoring
摘要： Frequent glucose monitoring is a fundamental part of diabetes management, and good glucose control is important for long-term health outcomes. New types of electrochemical sensors that allow for continuous glucose monitoring (CGM) have become an important tool for diabetes management, although they still have drawbacks such as short lifetime and a need for frequent calibration. Other technologies are still being researched for CGM, in an attempt to replace the electrochemical sensors. Optical methods have several advantages for CGM, including potentially long sensor lifetimes and short measurement times, and many developments have been made over the last decades. This paper will review optical measurement methods for CGM, their challenges, and the current research status. The different methods will be compared, and the future prospects for optical methods will be discussed.
关键词： Optical spectroscopy,glucose sensors,continuous glucose monitoring,quantitative optical methods,biomedical applications
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Portland, OR, USA (2018.11.13-2018.11.14)] 2018 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Micro-Structured Fiber as Temperature Sensor in a Loop Architecture
摘要： A temperature sensor built by a micro-structured fiber (MSF) into a Sagnac interferometer scheme is reported. The optical waveguide is provided by a two-hole fiber (THF) which are located asymmetrically from the core. A linear response to thermal effects is observed and the sensitivity 2.22 nm/°C was reached using a 2m-long of THF. The main advantage of the system proposed is a linear response, the use of a MSF with a simpler filled transverse geometry, non-use a special mechanism for the holes and a simple experimental array.
关键词： fiber optic,temperature sensor,micro-structured fiber,fiber sensors
更新于2025-09-09 09:28:46
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[Advances In Atomic, Molecular, and Optical Physics] Volume 66 || Efficient Description of Bose–Einstein Condensates in Time-Dependent Rotating Traps
摘要： Quantum sensors based on matter-wave interferometry are promising candidates for high-precision gravimetry and inertial sensing in space. The favorable sources for the coherent matter waves in these devices are Bose–Einstein condensates. A reliable prediction of their dynamics, which is governed by the Gross–Pitaevskii equation, requires suitable analytical and numerical methods, which take into account the center-of-mass motion of the condensate, its rotation, and its spatial expansion by many orders of magnitude. In this chapter, we present an efficient way to study their dynamics in time-dependent rotating traps that meet this objective. Both an approximate analytical solution for condensates in the Thomas–Fermi regime and dedicated numerical simulations on a variable adapted grid are discussed. We contrast and relate our approach to previous alternative methods and provide further results, such as analytical expressions for the one- and two-dimensional spatial density distributions and the momentum distribution in the long-time limit that are of immediate interest to experimentalists working in this field of research.
关键词： Bose–Einstein condensates,Thomas–Fermi approximation,matter-wave interferometry,Gross–Pitaevskii equation,quantum sensors
更新于2025-09-09 09:28:46
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Lorentz Reflect-Phase Detector for Moisture and Dielectric Sensing
摘要： We experimentally investigate a new class of resonant dielectric sensors that are based on reflectance phase measurement in the Lorentzian dispersion regime. The Lorentzian dispersion, also known as anomalous dispersion, is characterized by a strong wave absorption accompanied by a double reversal of the phase (flip-flop phase). Since the Kramer-Kronig relation holds, a phase-slope measurement is enough to completely characterize a dielectric material at in the narrowband microwave spectrum. Due to strong dispersion, the Lorentz sensors are noise immune and are less affected by external circuit changes. Therefore, they can be potentially applied in hostile environments such as high temperature furnaces. The proposed detection method is inspired from the optical measurement technique known as spectroscopic ellipsometry. We apply the anomalous phase detection to estimate dielectric and moisture changes.
关键词： dielectric sensing,microstrip resonators,anomalous dispersion,Lorentzian dispersion,resonant sensors,noise immunity
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE Photonics Conference (IPC) - Reston, VA, USA (2018.9.30-2018.10.4)] 2018 IEEE Photonics Conference (IPC) - Measuring Thermal Acoustic Radiation with an Optomechanical Antenna
摘要： We optically probe the SiN membrane nanomechanical resonator modes that are strongly coupled to acoustic radiation into the substrate. We use this optomechanical system for temperature metrology by detecting the ballistic transport of thermal excitations from a remote bath.
关键词： Metrology,Temperature Sensors,Optomechanics,Photonics,Thermal Noise,Nanophotonics
更新于2025-09-09 09:28:46
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Two-Pronged Motion Artifact Reduction for Wearable Photoplethysmographic Biosensors
摘要： Motion artifact poses a big challenge in photoplethysmography (PPG) for it greatly increases the difficulties of extracting the signal of interest accurately and reliably. Various techniques have been put forward in the past to tackle the issue. While these techniques have focused exclusively on artifact reduction, we attack the problem on two fronts. By integrating the auxiliary sensor and exploiting its correlations with the optical PPG sensor, not only do we cancel the artifacts but also, at the same time, enhance the signal of interest. Enhancing the signal of interest equivalently boosts the artifact reduction. The experiments have shown that the strategy performs rather effectively: The 95% limits of agreement (LOA) after the artifact reduction has been reduced down to less than one third of the LOA before the artifact reduction and is only three fourths as much as that of the artifact-free PPG.
关键词： biological sensors,Sensor systems,photoplethysmography (PPG),motion artifacts
更新于2025-09-09 09:28:46
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CuO Thin Films Functionalized with Gold Nanoparticles for Conductometric Carbon Dioxide Gas Sensing
摘要： Metal oxides (MOx) are a well-established material for gas sensing. MOx-based gas sensors are sensitive to a wide variety of gases. Furthermore, these materials can be applied for the fabrication of low-cost and -power consumption devices in mass production. The market of carbon dioxide (CO2) gas sensors is mainly dominated by infra-red (IR)-based gas sensors. Only a few MOx materials show a sensitivity to CO2 and so far, none of these materials have been integrated on CMOS platforms suitable for mass production. In this work, we report a cupric oxide (CuO) thin film-based gas sensor functionalized with gold (Au) nanoparticles, which exhibits exceptional sensitivity to CO2. The CuO-based gas sensors are fabricated by electron beam lithography, thermal evaporation and lift-off process to form patterned copper (Cu) structures. These structures are thermally oxidized to form a continuous CuO film. Gold nanoparticles are drop-coated on the CuO thin films to enhance their sensitivity towards CO2. The CuO thin films fabricated by this method are already sensitive to CO2; however, the functionalization of the CuO film strongly increases the sensitivity of the base material. Compared to the pristine CuO thin film the Au functionalized CuO film shows at equal operation temperatures (300 ?C) an increase of sensitivity towards the same gas concentration (e.g., 2000 ppm CO2) by a factor of 13. The process flow used to fabricate Au functionalized CuO gas sensors can be applied on CMOS platforms in specific post processing steps.
关键词： metal oxides,CMOS integration,CO2,gas sensors,CuO
更新于2025-09-09 09:28:46
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Planar Microstrip Ring Resonator Structure for Gas Sensing and Humidity Sensing Purposes
摘要： A planar microstrip ring resonator structure on alumina was developed. It was covered with a zeolite film. The device was successfully operated at around 8.5 GHz at room temperature as a humidity sensor. In the next step, an additional planar heater will be included on the reverse side of the resonator structure to allow for testing of gas sensitive materials under sensor conditions.
关键词： zeolite in operando spectroscopy,radio frequency gas sensing (RF),microwave sensors
更新于2025-09-09 09:28:46
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Metasurface-Based THz Dual-Band Absorber Sensor for the Measurement of Refractive Index Variations of Chemical and Biological Substances
摘要： In this paper we report on the results of the simulations of the electromagnetic properties of a metasurface composed of a 2D-array of plasmonic nanoantennas acting as polarisation insensitive dual band THz perfect absorber able to achieve absorption coefficients and quality factors up to 99.6% and 122, respectively. The 2D-array is designed on top of a polyimide flexible film separating it from an Ag ground layer. The plasmonic nanoantenna is composed of two Ag quadrangular rings and an Ag diamond-shape dot is placed at their geometrical centre. The absorption resonances show a linear frequency shift with respect to variations of the refractive index of transparent substances adsorbed on the metasurface. This allows the dual-band absorber to be employed as a sensor of the chemical/physical modifications taking place on the substance. In particular, in terms of the refractive index units, the sensor based on the dual-band absorber can achieve sensitivities up to 310 GHz/RIU.
关键词： THz perfect absorber,functionalised metasurfaces,plasmonic sensors
更新于2025-09-09 09:28:46