An oscillation-based active humidity sensing system with high sensitivity and wide range measurement

Enhancement of SPR effect and sensing characteristics in D-shaped polished grapefruit microstructured optical fiber with silver film

This paper presents a novel fiber liquid pressure sensor that uses photopolymer glue to generate Fabry-Perot (F-P) interference, resulting in high sensitivity (5.70 nm/kPa) and wide measurement range (0−500 kPa).

Fiber optic-based cryogenic temperature sensing has vital applications in aerospace, biomedicines, food, and energy storage. However, the current fiber optic-based cryogenic temperature sensors have the problems of low sensitivity and narrow sensing range. In this study, we experimentally investigated the cryogenic temperature sensing based on an all-fiber Sagnac loop using a panda polarization maintaining fiber (PPMF) and a fiber Bragg grating (FBG). Modeling simulation of PPMF under cryogenic temperature proved that it could be used for cryogenic temperature sensing in Sagnac loop. FBG, which showed a low but linear temperature response, was used to mark the dip wavelength in Sagnac loop as the movement of dip wavelength exceeding a free spectrum range (FSR). The proposed sensor showed a temperature measurement sensitivity of 0.943 nm/℃ and a wide measurement range of -103.15-46.85 ℃. Furthermore, the proposed sensor also depicted good hysteresis and stability. The study in this paper, which provides an idea to detect cryogenic temperature with high sensitivity and wide measurement range, offers a choice for remote and precise monitoring of cryogenic temperature.

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

Optical thermometry, due to its properties such as rapid response, usability, high sensitivity, and remote measurements, is gaining increasing interest among researchers. Particularly promising materials for low-temperature thermometry applications are metal-organic frameworks (MOFs) containing chromium(III) ions. In this work, we present a method for optimising data for the development of a temperature sensor, with particular focus on the relative sensitivity parameter (Sr). As part of the optimisation process, we distinguish two approaches using different data analysis techniques and observe the impact of individual parameters on the temperature characteristics of the materials. Additionally, we present the structural and spectroscopic properties of a series of [EA]MgxCr1-x(HCOO)3, where EA = ethylammonium cation, and x = 0, 0.01, 0.03, and 0.05. These materials are characterised by a perovskite structure and exhibit a strong dependence of spectroscopic properties on the concentration of the dopant and temperature. The luminescence properties of chromium(III) ions change due to variations in the crystal field strength (Dq/B), which is measured using diffuse reflectance spectroscopy and photoluminescence techniques. The investigated materials exhibit particular temperature-dependent luminescence, which can be implemented as a basis for the thermometric model determination. Moreover, the influence of temperature on luminescence lifetime provides a secondary thermometric pathway, which has not been reported for hybrid formate perovskites before. The obtained optical ratiometric sensors are characterized by high relative sensitivity (up to 3.07% K-1 at 130 K) and a wide operating range (up to 80-170 K interval). The thermometric analysis of the lifetime-based model shows high relative sensitivity up to 2.97% K-1 (140 K). In this work, we investigated the influence of the chemical composition on the observed thermometric performance within a series of EA-based hybrid compounds and compared two thermometric approaches - ratiometric and lifetime-based. What is more, we provide a comprehensive comparison of the spectroscopic properties, especially concerning the thermometric potential, with those of other reported hybrid formates, differing in the type of organic cation. The presented results show a particular potential of hybrid formate perovskites doped with Cr3+ ions, especially within the context of highly sensitive luminescence thermometry.

A Mach-Zehnder interferometer-coupled microring is experimentally demonstrated for optical sensing with a high sensitivity (~111 nm /RIU), a high extinction ratio (>26dB), and a very large quasi free-spectral-range (>100 nm), which helps to obtain a large measurement range. The MZI-coupled microring sensor still has good performance when the reflective index of the ambient materials largely changes (1<n<1.538).

High-sensitivity gas pressure sensor with low temperature cross-talk based on Vernier effect of cascaded Fabry-Perot interferometers

A Mach–Zehnder interferometer-coupled microring is experimentally demonstrated for optical sensing with a high sensitivity (~111 nm /RIU), a high extinction ratio (>26dB), and a very large quasi free-spectral-range (>100 nm), which helps to obtain a large measurement range. The MZI-coupled microring sensor still has good performance when the reflective index of the ambient materials largely changes (1<n<1.538).

Here novel chromogenic photonic crystal sensors based on smart shape memory polymers (SMPs) comprising polyester/polyether-based urethane acrylates blended with tripropylene glycol diacrylate are reported, which exhibit nontraditional all-room-temperature shape memory (SM) effects. Stepwise recovery of the collapsed macropores with 350 nm diameter created by a "cold" programming process leads to easily perceived color changes that can be correlated with the concentrations of swelling analytes in complex, multicomponent nonswelling mixtures. High sensitivity (as low as 10 ppm) and unprecedented measurement range (from 10 ppm to 30 vol%) for analyzing ethanol in octane and gasoline have been demonstrated by leveraging colorimetric sensing in both liquid and gas phases. Proof-of-concept tests for specifically detecting ethanol in consumer medical and healthcare products have also been demonstrated. These sensors are inexpensive, reusable, durable, and readily deployable with mobile platforms for quantitative analysis. Additionally, theoretical modeling of solvent diffusion in macroporous SMPs provides fundamental insights into the mechanisms of nanoscopic SM recovery, which is a topic that has received little examination. These novel sensors are of great technological importance in a wide spectrum of applications ranging from environmental monitoring and workplace hazard identification to threat detection and process/product control in chemical, petroleum, and pharmaceutical industries.

A practical optical fiber sensor is proposed for hydraulic pressure measurement. A thin-walled cylinder is used as the sensing device, which will be deformed with the applied pressure. Two fiber Bragg gratings (FBGs) are used in the sensor probe. One is stuck on the outer wall of thin-walled cylinder along the circumferential direction to measure the deformation of the cylinder. The other FBG is stuck in the groove which is on the top of the thin-walled cylinder and acts as a temperature measurement device. The accurate pressure can be obtained by monitoring the difference of the two shifted Bragg wavelengths. Theoretical relation between the wavelength shift difference and pressure has been established by the theoretical analysis. Meanwhile, the experiments have been carried out to verify the feasibility. Experiment results show that the sensitivity of the proposed pressure sensor is 69.4 pm/MPa in the region of $0\sim 16$ MPa. Compared with other references, the proposed pressure sensor in this letter is more compact with good sensitivity and wide measurement range.

Many areas of biological research demand the combined use of different imaging modalities to cover a wide range of magnifications and measurements or to place fluorescent patterns into an ultrastructural context. A technically difficult problem is the efficient specimen transfer between different imaging modalities without losing the coordinates of the regions-of-interest (ROI). Here, we report a new and highly sensitive integrated system that combines a custom designed microscope with an ultramicrotome for in-resin-fluorescence detection in blocks, ribbons and sections on EM-grids. Although operating with long-distance lenses, this system achieves a very high light sensitivity. Our instrumental set-up and operating workflow are designed to investigate rare events in large tissue volumes. Applications range from studies of individual immune, stem and cancer cells to the investigation of non-uniform subcellular processes. As a use case, we present the ultrastructure of a single membrane repair patch on a muscle fiber in intact muscle in a whole animal context.

A load sensor with high sensitivity, a wide measurement range, and a small size was developed by using an AT-cut quartz crystal resonator (QCR). The quartz crystal generates a charge that is proportional to the external force. Because it has high sensitivity and excellent temperature stability, it has been used for various sensors. In particular, a QCR has an inherently superior static-load-sensing characteristic. However, a QCR is fragile and easily broken by a stress concentration. Moreover, a retention mechanism is required to efficiently transmit the load, and it is necessary to fix the QCR firmly to avoid a horizontal force. Moreover, it is very difficult to miniaturize the retention mechanism because the fabrication and assembly process is complicated. We previously proposed a miniaturized sensor element that was developed using microfabrication. The QCR load sensor had an enormously wide force-sensing range of greater than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> N. However, the output was easily affected by a change in the parasitic capacitance around the QCR. The objective of this study was to improve the load-measurement resolution and stabilize the sensor output for application to biological signal detection. We fabricated a QCR sensor with a sensitivity of 973 Hz/N and succeeded in detecting multiple biological signals (respiration, heartbeat, and posture) with using proposed QCR load sensor.

In this paper, a high-sensitivity distributed optical fiber salinity sensor based on frequency-scanning phase-sensitive optical time-domain reflectometry (φ-OTDR) and polyimide-coated single-mode fiber is proposed. Distributed salinity sensing over an 1100 m polyimide-coated fiber with a 1 m spatial resolution was demonstrated, and a sensitivity of 782.4 MHz/(mol/L) was achieved with the salinity changing from 0 mol/L to 1.61 mol/L. Then the measurement accuracies of frequency shift and salinity were evaluated theoretically and experimentally. Both theoretical and experimental results show that the measurement accuracy deteriorates as the pulse width decreases, resulting in a trade-off between the spatial resolution and measurement accuracy. The measurement uncertainty of salinity is 0.022 mol/L in the case of 30 cm spatial resolution. And when the spatial resolution is set to be 2 m, the measurement uncertainty of salinity decreases to 0.005 mol/L. The response time of the fiber to external salinity change has also been investigated, and it takes about 8 minutes for the fiber to reach a stable state. The proposed salinity sensor exhibits high sensitivity and long measurement range, which may be used for distributed marine environmental monitoring.

A novel, ultrahigh-sensitivity wide-range resonant micro-accelerometer using two differential double-clamped monolayer graphene beams is designed and investigated by steady-state simulation via COMSOL Multiphysics software in this paper. Along with stiffness-enhanced optimized folded support beams, two symmetrical 3-GPa prestressed graphene nano-beams serve as resonant sensitive elements with a size of 10 μm × 1 μm (length × width) to increase the acceleration sensitivity while extending the measurement range. The simulation results show that the accelerometer with cascade-connected graphene and proof-mass assembly exhibits the ultrahigh sensitivity of 21,224 Hz/g and quality factor of 9773 in the range of 0–1000 g. This is remarkably superior to previously reported studies characterized by attaching proof mass to the graphene components directly. The proposed accelerometer shows great potential as an alternative to quartz and silicon-based resonant sensors in high-impact and highly sensitive inertial measurement applications.

A microfiber interferometer based on a single-mode tapered-no-core single-mode (STNCS) fiber structure coated with a thin layer of graphene oxide (GO) was proposed and demonstrated as a relative humidity (RH) sensor. The STNCS fiber structure has a strong evanescent field, which can sensitively response to changes in the surrounding refractive index. The moisture-sensitive material GO was used to form the film on the no-core fiber by a dip impregnation method. The effects of GO concentration and the tapered waist diameter on RH sensitivity were studied experimentally. The experimental results showed that a thinner waist diameter provides higher RH sensitivity. When the concentration of GO solution is 0.01 mg/mL, the STNCS fiber structure with a waist diameter of 2.9 μm performs better in RH sensing; a high sensitivity of 0.461 nm/%RH in the range of 40-98% was achieved. The sensor has good stability with wavelength fluctuations of ±0.009 nm and ±0.008 nm over 60 mins at RHs of 50% and 80%, respectively. The proposed fiber optic humidity sensor has a high sensitivity over a wide measurement range and offers good stability showing promising potential application in the field of RH sensing.