Resistance strain force sensors have been applied to monitor the strains in various parts and structures for industrial use. Here, we review the working principles, structural forms, and fabrication ...processes for resistance strain gauges. In particular, we focus on recent developments in resistance stress transfer for resistance strain force sensors and the creep effect due to sustained loads and/or temperature variations. Various error compensation methods to reduce the creep effect are analyzed to develop a metrology standard for resistance strain force sensors. Additionally, the current status of carbon nanotubes (CNTs), silicon carbide (SiC), gallium nitride (GaN), and other wide band gap semiconductors for a wide range of strain sensors are reviewed. The technical requirements and key issues of resistance strain force sensors for future applications are presented.
A stabilized narrow-linewidth random fiber laser for strain detection, based on a three-grating ring (TGR) resonator and half-open-cavity structure, is proposed and investigated experimentally. The ...half-open-cavity structure proved to provide double optical gain of erbium-doped fiber, which was beneficial to increase the photon lifetime as well as further narrow the linewidth. Meanwhile, the stability and frequency noise of narrow lasing output was improved by suppressing the competition-induced undesired residual random lasing modes with the TGR resonator. The TGR resonator is composed of a double-cavity fiber Bragg grating Fabry–Perot (FBG-FP) interferometer, a section of single-mode fiber, and a circulator. The specially designed double-cavity FBG-FP interferometer embedded in the TGR resonator acted as the strain-sensing element and improved the resolution of the dynamic strain. A stable ultra-narrow linewidth of about 205 Hz was obtained. The frequency noise was reduced to about 2 Hz/√Hz. A high dynamic strain measuring resolution of 35 femto-strain (fε)/√Hz was achieved.
In this paper, the influence of laser wavelength instability, polarization fading and phase fluctuation on local heterodyne detection wavelength scanning Brillouin optical time domain reflectometer ...(WS-BOTDR) is theoretically analyzed, and a local heterodyne detection WS-BOTDR system is built for experimental verification. The experimental results show that with the increase of sensing distance, the adverse effect of laser wavelength instability, polarization fading and phase fluctuation on local heterodyne detection WS-BOTDR is gradually aggravated, which will lead to the broadening and distortion of the wavelength power spectrum (WPS), resulting in large errors in demodulated Brillouin central wavelength (BCW) and temperature. The average temperature measurement errors at the positions of 1 km, 5 km, 9 km non-heating section and 9.45 km heating section are 1.76 °C, 3.42 °C, 3.89° C and 4.3 °C, respectively.
Summary
Wound infection is a challenging clinical problem that imposes substantial economic and psychological burdens on patients. However, the wound covered by a dressing is in an ‘unknown’ state. ...Recently, researchers have focused on understanding the condition of the wound without removing the dressing. Here, we presented a flexible integrated sensing platform (FISP) that can monitor multiple indicators, including local temperature. The platform consists of a flexible sensor chip (FSC), a controlled printed circuit board (CPCB) and a customized application installed on a smartphone that can receive and display data from the sensor chip through Bluetooth Low Energy 4.0 (BLE4.0) and upload real‐time wound information. This device exhibits satisfactory measurement accuracy, stability, durability, skin compliance and biocompatibility. It was applied to infected wounds on the back of rabbits to reveal the temperature changes characteristic of wounds infected with different bacteria, and this information was compared with the changes in the core body temperature of animals. We found differences in the temperature among wounds infected with different pathogens and the temperature of the wound infection occurred earlier than the change in anal temperature. The combined application of the FISP and dressings might help identify the ‘unknown’ state of wounds in the clinic.
We presented a flexible integrated sensing platform that can monitor multiple indicators, including local temperature. We found differences in the temperature among wounds infected with different pathogens and the temperature of the wound infection occurred earlier than the change in anal temperature. The combined application of the FISP and dressings might help identify the ‘unknown’ state of wounds in the clinic.
An all-fiber Mach-Zehnder interferometric (MZI) sensor for measuring temperature and refractive index (RI) is proposed and experimentally demonstrated. A high sensitivity balloon-like mode ...interferometer is fabricated with a twin-core and twin-hole fiber (TCTHF). The variations in ambient temperature and RI cause changes in phase differences between the modes, leading to shifts in the interference spectrum. The two resonance dip wavelength shifts within the spectrum are used to investigate the temperature and RI characteristics of the sensor. Experimental results show that the two dips have different responses to temperature and RI, indicating that the sensor can realize simultaneous measurement of temperature and RI. The obtained maximum sensing sensitivities are 0.051 nm/°C and 423.168 nm/RIU. The proposed sensor has potential applications in physical, biological, and chemical sensing owing to its high sensitivity, low cost, and small size.
To calibrate transfer standards for length calibration, a non-contact calibration system for step gauges and gauge blocks has been developed, in which a laser interferometer was equipped to obtain ...the length displacement and dual-stage driving-position techniques were used to carry step gauges to approach the measuring location. A non-contact collimation technique combined with an optoelectronic microscope was proposed for achieving identification. The optoelectronic microscope eliminates both the contact deformation resulting from the mechanical force and motion deviations. The combination of dual-stage driving-position techniques and the non-contact collimation technique can ensure that the collimation repeatability is less than 20 nm. The experimental tests and comparison results indicated that the non-contact strategy and dual-stage position techniques can provide a reliable method for building a length calibration system for gauges, industrial line scales, and end bars.
An all fiber Mach-Zehnder interferometric (MZI) sensor for measuring temperature and refractive index (RI) is proposed and experimentally demonstrated. The proposed sensor is fabricated with a ...coreless-few mode-coreless fiber structure. Variations in ambient temperature and RI cause changes in phase differences between the fundamental mode and the higher-order modes, leading to shifts in interference spectrum. The two resonance dips shifts within the wavelength spectrum are used to investigate the temperature and RI characteristics of the sensor. Experimental results show that the two dips have different responses to temperature and RI, indicating that the sensor can realize simultaneous measurement of temperature and RI; the maximum sensing sensitivities are 0.0739 nm/°C and −25.29 nm/RIU, respectively. The proposed sensor has potential applications in physical, biological, and chemical sensing owing to its low cost, good linearity, and simple fabrication.
A distributed fiber sensor was fabricated by splicing two single-mode fibers (SMFs) using the few-mode fiber (FMF) technique. A Brillouin optical time domain analysis (BOTDA) system was developed to ...measure the sensor’s temperature and bending performance. Two-mode and four-mode step FMFs were combined to splice the few-mode segment. The results indicate that the temperature response coefficients of the few-mode segment are only slightly higher than those of the connected single-mode segment, measuring at 1.13 MHz/°C and 1.12 MHz/°C, respectively. The minimum bending radius for the sensor is 0.9 cm, and the four-mode bending response curve is superior to that of the two-mode one, proving that 4-SI-FMF offers better bending sensitivity.
Metal corrosion is of worldwide concern because it is the cause of major economic losses, and because it creates significant safety issues. The mechanism of the corrosion process, as influenced by ...bacteria, has been studied extensively. However, the bacterial communities that create the biofilms that form on metals are complicated, and have not been well studied. This is why we sought to analyze the composition of bacterial communities living on steel structures, together with the influence of ecological factors on these communities. The corrosion samples were collected from rust layers on steel plates that were immersed in seawater for two different periods at Sanya and Xiamen, China. We analyzed the bacterial communities on the samples by targeted 16S rRNA gene (V3-V4 region) sequencing using the Illumina MiSeq. Phylogenetic analysis revealed that the bacteria fell into 13 phylotypes (similarity level = 97%).
,
and
were the dominant phyla, accounting for 88.84% of the total.
,
and
were the dominant classes, and accounted for 70.90% of the total.
spp.,
spp. and
spp. were the dominant genera and accounted for 45.87% of the total. These genera are sulfate-reducing bacteria that are known to corrode steel. Bacterial diversity on the 6 months immersion samples was much higher than that of the samples that had been immersed for 8 years (
< 0.001, Student's
-test). The average complexity of the biofilms from the 8-years immersion samples from Sanya was greater than those from Xiamen, but not significantly so (
> 0.05, Student's
-test). Overall, the data showed that the rust layers on the steel plates carried many bacterial species. The bacterial community composition was influenced by the immersion time. The results of our study will be of benefit to the further studies of bacterial corrosion mechanisms and corrosion resistance.
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