Temperature Self-compensation Research Articles

Few-mode optical fiber-based flexible pressure feedback tentacle doped with fluorescence temperature pointer

Abstract In this paper, a flexible fiber pressure feedback whisker is proposed, which consists of a water droplet shaped polydimethylsiloxane (PDMS) elastomer with an embedded balloon shaped few mode fiber. The mechanical sensing performance of the device was analyzed and optimized using a combination of finite element method and beam propagation method (BPM). The built-in cladding corroded few-mode fiber increases pressure sensitivity by more than four times. The collection efficiency of fluorescence signal is improved by cladding corrosion. The PDMS elastomer was doped with upconversion nanoparticles NaYF4:Yb, Er@NaYF4 in order to achieve temperature measurement by fluorescence intensity ratio technology. The combination of fluorescence signal and interference spectrum can not only achieve real-time and accurate pressure detection at different temperatures, but also incorporate fluorescent materials into flexible bionic skin for temperature self-compensation, which has potential application value for the development of bionic fiber micro-nano sensing and control devices.

Mechanical Structure Design of Pressure Sensors with Temperature Self-compensation for Invasive Blood Pressure Monitoring

Abstract Invasive blood pressure (IBP) is a fundamental part of basic cardiovascular monitoring. Conventional piezoresistive pressure sensors are limited in usage due to the high cost associated with equipment and intricate fabrication processes. Meanwhile, low-cost strain gauge pressure sensors have poor performance in the gauge factor (GF) and temperature insensitivity. Here, we report a mechanical structure design for diaphragm pressure sensors (DPSs) by introducing a compensation grid to overcome the aforementioned challenges. A simplified model is established to analyze the mechanical deformation and obtain the optimal design parameters of the DPS. By rationally arranging the placement of sensitive grids to eliminate the discrepancy of relative resistance changes within four arms of the Wheatstone full-bridge circuit, the appropriate GF and high temperature insensitivity are simultaneously achieved. The blood pressure sensor with the DPS is then fabricated and characterized experimentally, which demonstrates an appropriate GF (ΔU/U0)/P = 3.56 × 10−5 kPa−1 and low temperature coefficient of voltage (ΔU/U0)/ΔT = 3.4 × 10−7 °C−1. The developed mechanical structure design offers valuable insights for other resistive pressure sensors to improve the GF and temperature insensitivity.

Robust high-Q quasi-BICs in double-layer high-contrast metagrating with temperature self-compensation for refractive index sensing

We propose a double-layer high-contrast metagrating structure with robust high-quality (Q) and temperature self-compensation for four-band refractive index sensing. The structure supports four-band symmetry-protected bound states in the continuum (SP-BICs) that transform into quasi-BICs as a result of structural symmetry breaking. However, the Q-factor of these quasi-BICs are limited by perturbation parameters, hampering practical fabrication. Interestingly, tuning the cavity length, we implement four-band Fabry–Pérot bound states in the continuum (FP-BICs) to transform the resonance mode back into high-Q quasi-BICs even at large perturbations. This approach is conducive to improving robustness and modulation freedom of Q-factors. In addition, we achieve temperature self-compensation by using the double-layer high-contrast metagrating consists of two materials with opposite thermo-optic (TO) dispersions. The simulation results indicate that the largest refractive index sensitivity is 470.9 nm RIU−1, its figure of merit is 427 818.2, and its Q-factor up to 9.3 × 105. The proposed double-layer high-contrast metagrating has potential application prospects for multiplex and high-performance sensing.

Dual-axis fiber Bragg grating tilt sensor based on universal joint structure

Inclination angle measurement is widely used in fields such as infrastructure health, power engineering safety, and earthquake monitoring. In response to the problem that existing inclinometers based on the pendulum structure can only measure a single axial inclination angle, a dual-axis Fiber Bragg Grating (FBG) tilt sensor based on a universal joint structure is proposed. SolidWorks was used to establish a sensor model and conduct theoretical analysis. The structural parameters of the sensor were optimized using the control variable method. Based on the optimization results, a physical sensor was developed, and an inclination and temperature testing system was set up for performance testing. The results show that within a measurement range of ± 5°, the sensitivities of the X and Y axes of the sensor are 229.8 pm/° and 224.9 pm/°, respectively, with a resolution of approximately 4.4 × 10-4°. The tilt accuracy of the sensor is approximately 0.48°, and it exhibits good creep resistance and stability during long-term measurements, as well as temperature self-compensation capabilities. The research results provide a new reference for the development of similar dual-axis tilt measurement sensors.

Dual-Mode Comb Plasmonic Optical Fiber Sensing.

Surface plasmon (SP) excitation in metal-coated tilted fiber Bragg gratings (TFBGs) has been a focal point for highly sensitive surface biosensing. Previous efforts focused on uniform metal layer deposition around the TFBG cross section and temperature self-compensation with the Bragg mode, requiring both careful control of the core-guided light polarization and interrogation over most of the C + L bands. To circumvent these two important practical limitations, we studied and developed an original platform based on partially coated TFBGs. The partial metal layer enables the generation of dual-comb resonances, encompassing highly sensitive (TM/EH mode families) and highly insensitive (TE/HE mode families) components in unpolarized transmission spectra. The interleaved comb of insensitive modes acts as wavelength and power references within the same spectral region as the SP-active modes. Despite reduced fabrication and measurement complexity, refractometric accuracy is not compromised through statistical averaging over seven individual resonances within a narrowband window of 10 nm. Consequently, measuring spectra over 60 nm is no longer needed to compensate for small temperature or power fluctuations. This sensing platform brings the following important practical assets: (1) a simpler fabrication process, (2) no need for polarization control, (3) limited bandwidth interrogation, and (4) maintained refractometric accuracy, which makes it a true game changer in the ever-growing plasmonic sensing domain.

High-performance optical fiber differential urea sensing system for trace urea concentration detection with enhanced sensitivity using liquid crystals

A compact optical fiber differential sensing system consisting of microfiber interferometer (MFI) functionalized urease combined with stearic acid (SA)-doped 4-cyano-4′-pentylbiphenyl (5CB) and two fiber Bragg gratings (FBGs) for urea detection has been proposed and experimentally demonstrated. The SA-doped 5CB plays an important role of sensing signal amplification in urease specific recognition of urea. The hydrolysis reaction between urea and urease at the microfiber surface causes the deprotonation and self-assembly of SA, which further induces the reorientation of 5CB from planar alignment to homeotropic alignment. This process can be captured and transduced into the macroscopic wavelength shift of the MFI and power difference of two FBGs in the differential sensing system. The experimental results show that the differential sensing system can effectively detect urea in artificial urine, where the sensitivity of MFI is 3.85 nm/mM with a detection limit of 0.03 mM and the power difference sensitivity of two FBGs is 15.05 dB/mM with a detection limit of 0.01 mM within low concentration range of 0.01–0.1 mM. Furthermore, the differential sensing system has good selectivity, affordability, and temperature self-compensation. Therefore, the differential sensing system can be used as a sensitive method for urea detection and has potential applications in human health detection.

Head surface strain measurement based wireless bolt sensor with self temperature compensating

Bolt loosening detection is crucial for ensuring the safe operation of equipment. Loosened bolts are hard to detect, and if left undetected, it can lead to catastrophic failures, especially for numerous bolts in large-scale structures. Therefore, the development of distributed bolt monitoring method and related sensors is highly necessary. In this paper, a novel bolt preload sensor with self-temperature compensation is proposed, based on the strain distribution of the bolt head end face. This study enhances previous research by conducting a detailed analysis of strain distribution at the edge of the bolt head surface. The finite element analysis results show that the bolt preload has almost no effect on the circumferential strain in the edge region of bolt head surface. Based on this feature, the strain gauge is applied circumferentially along the edge of the bolt head face as a temperature compensation gauge. In this way, the measuring strain gauge and the temperature compensation gauge can be integrated on the surface of the bolt head, thus achieving self-temperature compensation for the sensor. An experimental device has been established and the experimental results show that the designed sensor has excellent linearity to the bolt preload and effective temperature compensation. For the monitoring of numerous bolts with a wide distribution, a wireless sensing network utilizing the proposed sensor has been designed. The proposed wireless bolt sensor is easy to install and replace, without redesigning or changing the existing structure, thus providing a simple and effective way to monitor large number of bolts with wide distribution.

Temperature Self-Compensating Intelligent Wireless Measuring Contact Lens for Quantitative Intraocular Pressure Monitoring.

Flexible bioelectronic devices that can perform real-time and accurate intraocular pressure (IOP) monitoring in both clinical and home settings hold significant implications for the diagnosis and treatment of glaucoma, yet they face challenges due to the open physiological environment of the ocular. Herein, we develop an intelligent wireless measuring contact lens (WMCL) incorporating a dual inductor-capacitor-resistor (LCR) resonant system to achieve temperature self-compensation for quantitative IOP monitoring in different application environments. The WMCL utilizes a compact circuitry design, which enables the integration of low-frequency and high-frequency resonators within a single layer of a sensing circuit without causing visual impairment. Mechanically guided microscale 3D encapsulation strategy combined with flexible circuit printing techniques achieves the surface-adaptive fabrication of the WMCL. The specific design of frequency separation imparts distinct temperature response characteristics to the dual resonators, and the linear combination of the dual resonators can eliminate the impact of temperature variations on measurement accuracy. The WMCL demonstrates outstanding sensitivity and linearity in monitoring the IOP of porcine eyes in vitro while maintaining satisfactory measurement accuracy even with internal temperature variations exceeding 10 °C. Overcoming the impact of temperature variations on IOP monitoring from the system level, the WMCL showcases immense potential as the next generation of all-weather IOP monitoring 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.

Modern approaches to determining the standardised parameters of vibration state of NPP steam pipelines

During the operation of NPP steam pipelines the main damaging factors are not only corrosion and erosion leading to thinning of the pipe wall but also fatigue damage resulting not only from temperature self-compensation efforts, but also high vibration load. As practice shows, the most promising direction of ensuring the vibration resistance of steam pipelines at present is the computational and experimental study of the stress-strain state of pipelines under vibration loading. This work shows that the strength of the most commonly used standard sizes of steel pipelines under the influence of vibration loads is determined in accordance with Russian State Standard R 59115.9-2021. Taking into account the stress concentration, the amplitudes of the conditional elastic reduced stresses were determined for the 4 variants of the calculation schemes accepted for consideration. The permissible amplitude of stresses from an operating condition of 60 years is determined. It is shown that the permissible voltage amplitude for the design temperature t = 350°C will be no more than 46.4 Mpa for a pipe made of 12X18H10T. As for NPP pipelines, the normalized vibration parameters in the regulatory documentation were not established until 2022, when the following vibration velocity limits were adopted for pipelines of nuclear power plants in Russian State Standard R 59115.11-2021, vibration resistance testing is not required: nmax up to 15 mm/s, nmsv up to 7 mm/s. Thus, currently in the Russian regulatory documentation there are no normalized values of vibration parameters (as a rule, vibration velocity) for pipelines selected depending on the frequency of vibration exposure. It is proposed to develop and introduce into the regulatory documentation frequency-dependent criteria for limiting vibration parameters of NPP pipelines, specified in accordance with the actual operating conditions of these pipelines.

Simultaneous measurement of hydrogen and methane concentrations with temperature self-calibration based on a SPR sensor with an anchor-shaped photonic crystal fiber

Hydrogen and methane are flammable and explosive gases, and their simultaneous measurement holds significant importance in applications of industrial safety and energy transmission. A high-sensitivity multi-parameter sensor based on the surface plasmon resonance (SPR) within an anchor-shaped photonic crystal fiber (AS-PCF) have been proposed and analyzed in detail, which can simultaneously measure hydrogen and methane concentrations while providing temperature self-compensation. To achieve simultaneous detection of hydrogen and methane, an open ring channel is introduced in both the x and y directions of the PCF. Each of these channels is coated with a layer of gold film and gas-sensitive films for hydrogen and methane, respectively. The designed AS-PCF structure is optimized to increase the reactive surface area between the gas and the gas-sensitive films, simultaneously enhancing the energy leakage of core modes to improve sensor performance. In addition, temperature sensitivity is augmented by filling PCF air holes with ethanol and enhancing the asymmetry of the fiber structure. The changes of gas concentration and environmental temperature are derived by demodulating the peak wavelength shifts in the loss and interference spectra. Simulation analysis demonstrates that the sensor can achieve average sensitivities of −0.23 nm/% for hydrogen and −4.84 nm/% for methane within the gas concentration range of 0.5 % to 3 %. Meanwhile, the temperature sensitivity can reach 0.58 nm/°C within the temperature range of 10 °C to 30 °C. This sensor demonstrates excellent linearity and high sensitivity, making it a promising tool for multi-gas measurements in various applications.

A resonant high-pressure microsensor based on a composite pressure-sensitive mechanism of diaphragm bending and volume compression

In this paper, a composite pressure-sensitive mechanism combining diaphragm bending and volume compression was developed for resonant pressure microsensors to achieve high-pressure measurements with excellent accuracy. The composite mechanism was explained, and the sensor structure was designed based on theoretical analysis and finite element simulation. An all-silicon resonant high-pressure microsensor with multiple miniaturized cavities and dual resonators was developed, where dual resonators positioned in two resonant cavities with suitably different widths are used to perform opposite characteristics in pressure and the same characteristics at different temperatures, which can improve pressure sensitivities and realize temperature self-compensation by differential frequency output. The microsensor was fabricated by microfabrication, and the experimental results showed that the sensor had an accuracy of ±0.015% full scale (FS) in a pressure range of 0.1~100 MPa and a temperature range of −10~50 °C. The pressure sensitivity of the differential frequency was 261.10 Hz/MPa (~2523 ppm/MPa) at a temperature of 20 °C, and the temperature sensitivities of the dual resonators were −1.54 Hz/°C (~−14.5 ppm/°C) and −1.57 Hz/°C (~−15.6 ppm/°C) at a pressure of 2 MPa. The differential output had an outstanding stability within ±0.02 Hz under constant temperature and pressure. Thus, this research provides a convenient solution for high-pressure measurements because of its advantages, namely, large range, excellent accuracy and stability.

Temperature self-compensation thin film strain gauges based on nano-SiO2/AgNP composites

Nano-SiO2/AgNP temperature self-compensation thin film strain gauges for micro-strain by direct ink writing technology.

A sub-millinewton resolution biaxial force sensor with temperature self-compensation for vascular intervention

This article presents a fiber Bragg grating (FBG)-based highly sensitive micro-biaxial force sensor for vascular intervention surgery. It features a 3D-printed integrated structure incorporating an FBG- embedded cavity at its front end for temperature decoupling and an elliptical arc ball hinge to improve lateral sensitivity. Four FBG-embedded fibers are suspended in a circular array within the flexible hinge to minimize lateral strain crosstalk and increase measurement accuracy. Finite-element analysis has been implemented to validate the flexure performance, while both static and dynamic loading experiments have been performed to validate the sensor performance. The experiments revealed resolutions of 0.761 and 0.765 mN, respectively for the two lateral forces within a range of −1 to 1 N, and dynamic measurement error lower than 0.67 % of full scale. Temperature compensation experiments are conducted under loaded conditions for both axes, showing errors of lower than 1.6 % and 1.2 %. The ability to decouple force and temperature will benefit its broad application for vascular intervention surgery.

Low-frequency FBG vibration sensors for micro-seismic monitoring

Vibration sensors are key components in low-frequency micro-seismic monitoring, and their performance directly determines the accuracy of monitoring results. In response to the current problem that fiber Bragg grating (FBG) vibration sensors are difficult to effectively monitor micro-seismic low-frequency vibration signals, a rigid L-shaped beam FBG vibration sensor based on bearings is proposed. Firstly, a sensor model is established and theoretically analyzed; secondly, key parameters are optimized using differential evolution algorithm and imported into COMSOL simulation software for static stress analysis and dynamic characteristic analysis; finally, the sensor prototype is developed and a low-frequency vibration test system is set up to verify the sensor performance. The results reveal that the inherent frequency of the sensor is 57 Hz, with a flat response band of 0.3–35 Hz, a frequency lower limit of 0.05 Hz, a transverse interference degree of 4.5%, an average sensitivity of over 800 pm g−1, a dynamic range of 67.75 dB, favorable linearity, and the ability to achieve temperature self-compensation. Research findings provide new insights into low-frequency micro-seismic monitoring.

Simultaneous crack and temperature sensing with passive patch antenna

This article presents a novel passive patch antenna sensor for simultaneous crack and temperature sensing, and the antenna sensor has the ability of temperature self-compensation. The passive patch antenna sensor consists of an underlying patch and an overlapping sub-patch. The off-center feeding activates resonant modes in both transverse and longitudinal directions. The resonant frequency shift in transverse direction is used for environmental temperature sensing, while the structural crack width can be sensed by the longitudinal resonant frequency shift after temperature compensation. Furthermore, the unstressed design of the antenna can also eliminate the issue of incomplete strain transfer ratios. In this article, the relationships between the antenna resonant frequencies, the environmental temperature, and the structural crack width were studied. Simulations were conducted to determine the optimal off-center fed distance of the patch antenna sensor. Furthermore, a series of experimental tests were also conducted, where the passive patch antenna was fabricated and installed on the concrete components as well as an actual building. Continuous monitoring was performed for several days to test the temperature sensing ability of the passive patch antenna, and the sensed crack width after temperature compensation was compared with the actual results. The results of these experiments demonstrate the feasibility of using the passive patch antenna for simultaneous temperature and crack sensing.

High-sensitivity strain sensor with micron-scale imitation dumbbell structure based on differential temperature self-compensation

A micron-sized dumbbell-like -MZI structure has been developed using hydroxide flame melt taper and arc fusion discharge, with the dumbbell rod region prepared by melt taper drawing and the dumbbell sheet region prepared by arc fusion discharge. This structure has a sensitive light intensity response in the sensing field due to a double-order mode-field coupled excitation region. The geometrical parameters of the dumbbell-like system are optimized theoretically, and the feasibility of the microstructure to achieve high strain sensing sensitivity is analyzed. Experimental results show that the microstructure has a high strain sensing sensitivity of ∼ 0.074 dB/µε and a consistent temperature sensing sensitivity over the entire monitoring wavelength range. Therefore, a light intensity-dependent temperature self-compensation calculation is proposed to achieve a uniform light intensity-strain response for each characteristic peak in the monitored wavelength domain. Since the device has a significant advantage in light intensity modulation and is not affected by polarization light perturbations, it can be used as an alternative light intensity modulation device in optical communication networks and laser research. It can also be used as a probe for medical diagnostic testing based on its enhanced evanescent field properties.

Calibration Experiment and Temperature Compensation Method for the Thermal Output of Electrical Resistance Strain Gauges in Health Monitoring of Structures

Electrical resistance strain gauges are widely used in asymmetric structures for measurement and monitoring, but their thermal output in changing temperature environments has a significant impact on the measurement results. Since thermal output is related to the coefficient of thermal expansion of the strain gauge’s sensitive grating material and the measured object, the temperature self-compensation technique of strain gauges fails to eliminate the additional strain caused by temperature because it cannot match the coefficient of thermal expansion of various measured objects. To address this problem, in this study, the principle of the thermal output of electrical resistance strain gauges was analyzed, a calibration experiment for thermal output in the case of a mismatch between the coefficient of linear expansion of the measured object and the strain gauge grating material was conducted, and the mechanism for temperature influence on thermal output was revealed. A method was proposed to obtain the thermal output curves for different materials by using thermostats with dual temperatures to conduct temperature calibration experiments. A linear regression method was used to obtain a linear formula for the thermal output corresponding to each temperature. The thermal output conversion relationship was derived for materials with different coefficients of linear expansion. An in situ temperature compensation technique for electrical resistance strain gauges that separates the measured strain into thermal and mechanical strains was proposed. The results showed that the thermal output curve for the measured object can be calibrated in advance and then deducted from the measured strain, thus reducing the influence of temperature-induced additional strain on the mechanical strain. In addition, a new method was provided for the calculation of the thermal output among materials with similar coefficients of linear expansion, providing a reference for the health monitoring of asymmetric structures.

High-Temperature Self-Compensating Absolute Micro-Pressure Sensor and Its Testing Method

In this study, we designed an absolute pressure micro-pressure sensor, with its testing method based on the requirements of high-temperature resistance, self-compensation, and micro-pressure test. The substrate of the sensor is made of raw porcelain through high-temperature sintering, and the functional layer is integrated into the surface of the substrate by silver paste through a screen-printing process. Therefore, the sensor has high temperature resistance. The ceramic base of the sensor is prepared based on the principle of film stress and strain measurement of micro pressure by filling carbon film in raw porcelain layer and using a high-temperature sintering process to obtain an air-tight cavity structure. In the preparation of the functional layer, a unique differential capacitance structure is constructed on the surface of the substrate using the screen-printing process. This hardware temperature self-compensation structure enables the high-precision measurement of the sensor. Finally, the high temperature and absolute pressure micro-pressure sensor are combined with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> conversion circuit to complete the test on the high-temperature-micro pressure composite test platform. The experimental results show the sensor can measure the absolute pressure from 3 to 100 kpa in the temperature range of 23 °C to 300 °C, and the repeatability error of the pressure test is less than 3.3% at 300 °C.

A Bilayer Thin-Film Strain Gauge With Temperature Self-Compensation

A Karma–CuNi bilayer strain gauge with a low-temperature coefficient of resistance (TCR) is designed for temperature self-compensation. The impact of heat treatment and structural parameters on its performance is investigated. The TCR of the bilayer thin-film strain gauge can be adjusted to near 0 ppm/°C by controlling the thickness ratio and the annealing temperature. Besides, the Karma–CuNi thin films had a gauge factor (GF) of 2.2. Finally, the Karma–CuNi bilayer thin-film strain gauge was fabricated on the metal substrates and bone-like metal elastomer. An experimental setup based on bending beam theory was developed to determine the GF of the strain gauges fabricated on metal substrate. It shows promising applications for in situ strain or torque measurement of some metal component when high sensitivity and high spatial resolution is required.