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Abstract Passive temperature sensing systems based on the Internet of Things (IoT) present an efficient, reliable, and convenient solution for temperature monitoring with extensive application prospects and market value. This paper introduces a passive, battery-free, chipless, metasurface temperature sensing tag. The key insight is that the sensing tag uses vanadium dioxide ( $$\hbox{VO}_{2}$$ ) to solve the problems of measuring distance, large size, and high cost related to active devices. The sensing tag fabricated with tungsten-doped $$\hbox{VO}_{2}$$ powder demonstrated a significant variation in the reflection magnitude within the temperature range of 34–42 °C. It was achieved through coating, sintering, metasurface design, and ion beam etching. Experimental results showed that the square resistance of the prepared coating decreased from 1003 to 90 $${\Omega }/{\square }$$ as the temperature increased from 34 to 42 °C. Additionally, the reflection magnitude of the tag significantly increased with the temperature decrease in the 3.5–5.27 GHz frequency band. These results indicate that the passive temperature sensing tags can achieve rapid and accurate temperature sensing within the 34–42 °C range.

Rice husk is usually generated as waste in large quantities but yet to be optimally utilized. Due to the pollution effects associated with poor approach prevalently adopted for its disposal, valorizing it into economical and sustainable material for building construction is a necessary option to provide solution for future generation. In this research, separate dry mortars were prepared using cement grades 32.5R and 42.5N and the influence of rice husk ash (RHA) inclusion on their electrical characteristics was investigated. The materials used were batched by volume and the RHA was utilized as a partial substitute for cement at 10 % level. All the samples were cured for 21 days and then allowed to dry completely prior to the tests implementation. The results showed decrease in electrical resistance with temperature (ranging from 20oC to 50oC) due to incorporation of the RHA. Though samples with the RHA content possessed ability to act as smart mortars for temperature monitoring/sensing, utilization of cement grade 42.5N ensured a better performance. By utilizing rice husks in such undertakings, their associated disposal problems could be tackled and construction of inexpensive but sustainable building with large temperature sensing capability could be enhanced.

Understanding how cells sense temperature is a fundamental question in biology and is pivotal for the evolution of life. In numerous organisms, temperature is not only sensed but also generated due to cellular processes. Consequently, the mechanisms governing temperature sensation in various organisms have been experimentally elucidated. Extending upon others’ proposals and demonstration of protein- and nucleic acid-based thermosensors, and utilizing a colonial India ‘punkah-wallahs’ analogy, I present my rationale for the necessity of temperature sensing in every organelle in a cell. Finally, I propose temperature-sensing riboceptors (ribonucleic acid receptors) to integrate all the RNA molecules (mRNA, non-coding RNA, and so forth) capable of sensing temperature and triggering a signaling event, which I call as thermocrine signaling. This approach could enable the identification of riboceptors in every cell of almost every organism, not only for temperature but also for other classes of ligands, including gaseous solutes, and water.

Abstract The accurate characterization of local magnetic fields and temperature is vital for the design of electronic systems. To meet this imperative, we present a novel non-contact approach for simultaneous quantitative magnetic field imaging and temperature sensing using magnetooptics and a bismuth-doped yttrium iron garnet film with out-of-plane anisotropy. For the direct signal quantification, a Stokes polarization camera is employed in a conventional magnetooptical microscope. The magnetization in the garnet is modulated with an external magnetic field to continuously image the Faraday rotation at four distinct points along the saturating magnetization loop. The method enables sensing of the magnetooptical signal in saturation, the magnetooptical susceptibility, the temperature, and self-calibrated driftfree imaging of the out-of-plane magnetic field component. A spatial resolution of magnetic field in the micrometer range with millisecond exposure time is demonstrated. The method is verified by analyzing the stray magnetic field distribution of electrical current in a wire simultaneously to the Joule heating induced by the applied current.

Alternating current electroluminescent (ACEL) devices have attracted tremendous attention due to their significant applications in bioinspired electronics, smart wearables, and human-machine interfaces. However, it still faces limitations in real-time visual temperature sensing. Herein, a universal strategy is established to achieve real-time temperature dynamic visualization by integrating a thermochromic layer through a simple spin coating procedure. Such elaborate integration permits the device to display a wide array of luminous colors and achieve high-contrast color transitions in response to ambient temperature variations. More importantly, a quantitative relationship can be established between the temperatures and the luminous color changes. This advancement not only enhances multi-color emission capabilities but also enables the display of diverse information, marking a significant stride in the development of dynamic temperature sensing in ACEL devices.

Electronic textiles (e-textiles) build upon existing technologies to develop truly smart textiles: garments that sense, react, and adapt. Thermoregulatory e-textiles are an area of significant interest across the field. Designing e-textiles that satisfy electrical performance and simple construction is a significant challenge. To address these issues, a simple dip-coating and in-situ polymerization method was used to develop the first example of a thermoregulatory e-textile using green synthesized silver nanoparticles (AgNP) and polypyrrole (Ppy), based on the method previously reported (Naysmith, A.; Mian, N.S.; Rana, S. Development of conductive textile fabric using Plackett–Burman optimized green synthesized silver nanoparticles and in situ polymerized polypyrrole. Green Chemistry Letters and Reviews 2023, 16 (1)). This methodology was optimized using a Taguchi statistical design determining the optimal AgNP-Ppy synthesis method to obtain high performance Joule heating e-textiles, novel within the field of e-textiles. Reactant concentration and reaction time had the largest effects on the electrical resistance of subsequent e-textiles. The result is the first example of an e-textile heater based on green synthesized AgNPs. The e-textile demonstrated exceptional Joule heating (120°C), low electrical resistance (37 Ω), resistive temperature sensing behavior (negative TCR = −0.0046), and increased thermal conductivity (19.55 l (Wm−1 K−1)); the strain sensing behavior (gauge factor = −0.07). This work extends knowledge of the development and challenges within e-textile technologies as the field creates the next generation of textiles.

Light and temperature are the driving forces in plant development and growth. Specific photoreceptors provide the ability to sense and interpret light and temperature to regulate growth. Under the limited light conditions in most sports stadiums, natural grasses suffer from light deficiency. Artificial light provided by light-emitting diodes (LEDs) is used to increase their growth and adjust their development. Flavonoids like flavonols and anthocyanins are influenced by light conditions and temperature. Increased blue light can elevate the content of these secondary metabolites. Remote measurements of internal parameters using non-destructive methods provided information on their content under different temperature conditions for quality monitoring. This experiment tested flavonoid contents in Kentucky bluegrass (Poa pratensis) for different blue-to-red light ratios (0.6 and 0.4) and three temperature courses (constant temperature of 4 °C, constant temperature of 12 °C, and temperature switching among 12–8–4–8–12 °C). The results show elevated levels of flavonoids under blue-dominant artificial light as well as increased content under low-temperature (4 °C) conditions. The lack of flavonoids at elevated temperatures (12 °C), especially under red-dominant light, suggests an increased requirement for artificial blue light at increased temperatures. Non-destructive flavonoid determination was suitable for this experiment and can therefore be used for practical sports turf quality monitoring.

Enhancing sediment accumulation monitoring techniques in sewers will enable a better understanding of the build-up processes to develop improved cleaning strategies. Thermal sensors provide a solution to sediment depth estimation by passively monitoring temperature fluctuations in the wastewater and sediment beds, which allows evaluation of the heat-transfer processes in sewer pipes. This study analyses the influence of the flow conditions on heat-transfer processes at the water–sediment interface during dry weather flow conditions. For this purpose, an experimental campaign was performed by establishing different flow, temperature patterns, and sediment depth conditions in an annular flume, which ensured steady flow and room-temperature conditions. Numerical simulations were also performed to assess the impact of flow conditions on the relationships between sediment depth and harmonic parameters derived from wastewater and sediment-bed temperature patterns. Results show that heat transfer between water and sediment occurred instantaneously for velocities greater than 0.1 m/s, and that sediment depth estimations using temperature-based systems were barely sensitive to velocities between 0.1 and 0.4 m/s. A depth estimation accuracy of ±7 mm was achieved. This confirms the ability of using temperature sensors to monitor sediment build-up in sewers under dry weather conditions, without the need for flow monitoring. HIGHLIGHTS Combining temperature measurements and analysis of heat-transfer processes can be used to estimate sediment depths in sewers.; Neglecting hydraulic variables barely affected the accuracy of the depth estimations.; Temperature-based systems can be low-cost and easy to scale and implement in sewer systems.; These devices can lead to optimal inspection and cleaning strategies, as well as in other urban drainage systems.;

A facile one-step non-contact process was developed for preparing the substrates for Fabry-Perot-based side-polished optical fiber sensors. A carbon dioxide (CO2) laser cladding removal technique was used to control the profile of the polished fiber surface and to introduce two reflective cavities. The substrates were characterized for a range of cavity lengths and their thermal response was studied. This device added a degree of freedom to the design of optical fiber based Fabry-Perot sensors and its potential was demonstrated by coating the substrate with polydimethylsiloxane (PDMS). The resulting sensors had a three-order of magnitude increase in sensitivity when compared to the substrate. The polished flat surface provided a route for the integration of novel materials for sensing applications, particularly those where polarization control was vital for light-matter interaction, for example, low dimensional materials such as graphene or MXene. The inherent simplicity, mechanical stability, and scalability of this approach are important steps for the realization of practical devices of this type.

Abstract Objective The objective of this study is to assess the impact of overnight environmental conditions on erectile penile temperature within a controlled setting, with the aim of investigating the feasibility of using temperature measurements for nocturnal erection detection in erectile dysfunction diagnostics. Subjects/patients and methods We conducted a proof‐of‐concept study involving 10 healthy male participants aged 20 to 25. The study was carried out at the Department of Urology, St. Antonius Ziekenhuis, the Netherlands. Penile temperature thermistor measurements were taken during visually aroused erections of participants in naked state and in simulated overnight condition (underwear and blankets). Main outcome variables were peak and baseline temperature during erectile periods. To minimize the impact of differences in erectile strength and duration between consecutive measurements, we applied randomization to the order of the environmental conditions. Results We observed a significant increase in penile temperature during erection in both the naked (p

Abstract In this work, a plasmonic sensor based on metal–insulator–metal (MIM) waveguide for temperature sensing application is numerically investigated via finite element method (FEM). The resonant cavity filled with PDMS polymer is side-coupled to the MIM bus waveguide. The sensitivity of the proposed device is ~ − 0.44 nm/°C which can be further enhanced to − 0.63 nm/°C by embedding a period array of metallic nanoblocks in the center of the cavity. We comprehend the existence of numerous highly attractive and sensitive plasmonic sensor designs, yet a notable gap exists in the exploration of light coupling mechanisms to these nanoscale waveguides. Consequently, we introduced an attractive approach: orthogonal mode couplers designed for plasmonic chips, which leverage MIM waveguide-based sensors. The optimized transmission of the hybrid system including silicon couplers and MIM waveguide is in the range of − 1.73 dB to − 2.93 dB for a broad wavelength range of 1450–1650 nm. The skillful integration of these couplers not only distinguishes our plasmonic sensor but also positions it as a highly promising solution for an extensive array of sensing applications.

The electrical characteristics and conduction mechanisms of ZrAlN thin films for their potential use as thermistor sensors were assessed. Various compositions of Zr1-xAlxN were synthesized by sputtering and studied up to 200 °C to understand their sensitivity and applicability. Among the compositions studied, the ones with x = 0.34 and x = 0.46 showed the highest sensitivities, reaching values close to 3000 K. However, the thermo-resistive properties exhibited by these compositions limited their utilization above 100 °C. Zr1-xAlxN film compositions with x higher than 0.46 showed amorphous structures and were found to be insulative. Composition with x = 0.26, within the cubic phase, showed the most promising electrical properties regarding temperature sensing in the studied range. XPS analysis of this composition confirmed the presence of Zr-N and Al-N bonds, with a Zr3+ oxidation state, which suggests the availability of a free electron contributing to the electrical conduction. Impedance measurements performed at different temperatures for this composition revealed the dominant role of the grain boundaries in the conduction mechanism, based upon electron hopping between grains, overcoming the energy barrier imposed by the grain boundaries. ZrAlN thin films demonstrate negative temperature coefficient (NTC) thermistor behavior, expanding their applications beyond protective coatings to temperature monitoring.

This study investigates an approach to temperature sensing by integrating Titanium Aluminum Nitride (TiAlN), originally engineered for wear and corrosion applications, as a temperature sensor within a multilayered thin film system. A nitride multilayer system was developed by physical vapor deposition (PVD) using a single four-target magnetron sputtering chamber; intermediate vacuum interruption steps were employed for masking procedures. The multilayer architecture design aimed to provide the sensor layer with mechanical protection and electrical shielding. Structural and electrical characterization of the TiAlN single layer revealed semiconductor behavior and stable electrical resistance up to 750 °C, with minimal signal stabilization requirements. Despite the higher Al content, the TiAlN temperature sensor exhibited a cubic crystal structure characterized by diffuse nanolayers, resulting from a two-fold rotational deposition and target configuration. A detailed examination of the multilayer system cross-section containing the TiAlN sensor was conducted using scanning transmission electron microscopy (STEM). The analysis revealed its columnar morphology with the presence of typical PVD growth defects, including voids and droplets. While the presence of these defects may impact the electrical characteristics of the sensor, the selected experimental conditions effectively maintained the structural integrity of the multilayer system despite the vacuum interruptions caused by masking procedures. Validation experiments confirmed the functionality of the multilayer system for temperature measurements up to 400 °C. The signal acquisition system addressed room temperature resistance variations and low sensitivity (thermistor coefficient ∼100 K), resulting in a measured error of approximately 6%. This study demonstrates promising results of TiAlN as a temperature sensor within a multilayered system, expanding its range of potential applications.

Improvement of luminescent thermometers requires not only the search for high-sensitivity thermometric outputs, but also availability of multiple thermometric parameters affording a combined and reliable response. We hereby detail for the first time the luminescence of Eu3+ in manganese tungstate (Eu3+:MnWO4) solids obtained by coprecipitation under ultraviolet excitation and how this material provided an optical thermometric response from 77 K to 373 K via excitation and emission spectra. Processing of up to five thermometric parameters, namely bandwidths, band positions, band shifts and luminescence intensity ratios, resulted in relative thermal sensitivities as high as 1.56% K−1 and temperature uncertainties between 0.01 and 2 K depending on the choice of the spectral parameter. In addition, we demonstrate that Eu3+:MnWO4 also act as a qualitative colorimetric thermosensor because of progressive change of emission color to greenish-yellow to bluish-green upon heating under UV excitation. Therefore, our results show that the combination of broadband tungstate emissions with the 4f-4f narrow emissions of Eu3+ is an effective approach to achieve a multiparametric luminescent thermal response via emission, excitation and visual observation, which makes Eu3+:MnWO4 a promising candidate for advanced thermometry applications.

In this paper, a photonic skin sensor based on a balloon-shaped optical fiber structure cascading a Fiber Bragg Grating (FBG) is proposed, which can simultaneously sense pressure and temperature. When the photonic skin feels pressure, the built-in polymer micro-cap is squeezed, causing a change in the radius of the balloon-shaped structure. At the same time, the capillary-enclosed FBG can be used for temperature compensation. The pressure sensitivity of the photon skin sensor can reach 6.556 nm/mN in the range of 0-0.5 mN and the temperature sensitivity can reach -0.192 nm/°C in the range of 30-50 °C. The demodulation of the dual parameter matrix shows that the error rates of pressure and temperature measurements are less than 0.5% and 2.01%, respectively. On this basis, the sensor is applied to robotic arm-assisted puncture experiment detection, and the five states of the puncture process are analyzed. Based on the backpropagation (BP) neural network for repeated training, the results show that its accuracy remains at 98.7%, indicating that the sensor has good robustness. The development of this sensor shows application potential in the field of robotic intelligent skin in the future.

Respiration is one of the most important physiological processes of the human body. Continuous monitoring of respiration with wearable sensors can provide abundant information related to the health status of the respiratory system. However, the vast majority of the developed respiration sensors are constructed on nontextile substrates, resulting in dissatisfactory convenience, comfortness, and aesthetics. Additionally, special micro‐/nanomaterials are inevitably involved to construct the respiration sensors, which pose potential hazards to the human body due to the exfoliation and inhalation of these micro‐/nanomaterials. Here, humidity‐ and temperature‐sensitive electronic textiles (e‐Textiles) are presented, which are fabricated based on easily accessible and biofriendly materials (e.g., sodium chloride, glycerin, aluminum fiber, carbon fiber, and polyvinyl alcohol). Moreover, the proposed e‐Textiles use a potentiometric sensing mechanism, featuring self‐powered signal outputs and ultralow power consumption. The humidity and temperature‐sensing functionalities can also be in situ integrated into commercial masks for constructing full‐textile and all‐in‐one e‐Masks for comprehensive respiration monitoring. As demonstrations, both single‐point respiration monitoring (e.g., intensity, frequency, etc.) and 2D respiratory analysis (i.e., airflow distribution) can be realized with the e‐Masks. This work provides a facile and scalable approach to manufacture self‐powered and fully fabric respiration sensors for comprehensive respiratory analysis.

This research presents the design and implementation of a chipless Radio Frequency Identification (RFID) multi-sensor tag on a flexible laminate. Along with the tag's primary function of data encoding for object identification purposes, the tag also incorporates moisture and temperature sensing functionalities within a compact size measuring a mere 15 × 16 mm2. The tag structure comprises of a total 29 resonators, with each resonator corresponding to one bit in the microwave response. The initial design utilized the bendable Rogers RT/duroid®5880 within a frequency band of 5.48–28.87 GHz. To conduct a comprehensive comparative analysis, the tag design is optimized for two distinct substrates including Kapton®HN and PET. The optimization process involves exploring the utilization of both silver nanoparticle-based ink and Aluminum as radiators. The sensing feature was incorporated by deploying a thin film of Kapton®HN over the longest slot of the tag which acts as a moisture sensor. Temperature sensing feature was achieved by combining Stanyl® polyamide, a temperature dependent polymer, with Rogers RT/duroid®5880 which served as a fused substrate. The tag showcases a high code density of 12.08 bits/cm2 enabling it to efficiently label 229 unique items. Its unique features include flexibility, miniaturized design, printability, cost-effectiveness and multi sensing property.

In this study, we investigate micrometer-sized NaYF4 crystals double-doped with Yb3+/Er3+ lanthanide ions, designed for temperature-sensing applications. In contrast to previous studies, which focused predominantly on the high-temperature regime, our investigation spans a comprehensive range of both high and ultralow temperatures. We explore the relationship between temperature and the upconversion luminescence (UCL) spectra in both frequency and time domains. Our findings highlight the strong dependence of these spectral characteristics of lanthanide-doped NaYF4 crystals on temperature. Furthermore, we introduce a dual-mode luminescence temperature measurement technique, leveraging the upconversion emission intensity ratio for both green and red emissions. This study also examines the correlation between temperature sensing, energy level disparities, and thermal coupling in Er3+ ions across various temperature scales. Our research contributes to advancing the understanding and application of lanthanide-doped materials, setting a foundation for future innovations in temperature sensing across diverse fields.

Glass ceramics (GCs) containing PbS quantum dots (QDs) are prepared for temperature sensing. Broadband emissions are detected in the GCs when PbS QDs are precipitated from the glasses, and emissions centers are modulated from 1250 nm to 1960 nm via heat treatments. The emission centers of GCs exhibit blue-shifts when environment temperatures increase from room temperature to 210 °C. Importantly, the shift values of emission centers increase linearly with the test temperature, which is beneficial for applications in temperature sensing. A temperature sensor based on PbS QDs GC is heat-treated at 500 °C for 10 h, possesses the highest sensitivity of 0.378 nm/°C, and exhibits excellent stability and repeatability at high temperatures (up to 210 °C). Moreover, GC fibers are fabricated by using the GCs as the fiber core. The sensitivity of the temperature-sensing sensor of the GC fibers is also demonstrated and the sensitivity is as high as 0.558 nm/°C. The designed PbS QDs GCs provide a significant materials base for the manufacturing of fluorescent temperature sensors and the GC fibers offer significant opportunities for temperature detection in complex, integrated and compact devices.

Pr-doped metal oxide polycrystalline transparent ceramics are highly desirable for photothermal window systems served in extreme environments; however, obtaining efficient photoluminescence (PL) together with high transparency in these ceramics is still posing serious challenges, which undoubtedly limits their applications. Here, Pr-doped Y2Zr2O7 (YZO) transparent ceramics, as an illustrative example, are prepared by a solid-state reaction and vacuum sintering method. Owing to the elimination of defect clusters [PrY4+−O2−−PrY4+] and [PrY4+−e′] without the introduction of impurities and additional defects, the fabricated YZO:Pr ceramics exhibit high transparency (74%) and efficient PL (39-fold enhanced) after air annealing plus vacuum re-annealing treatment. Moreover, upon 295/450 nm excitation, the emission bands (blue, green, red, and dark red) from YZO:Pr ceramics present different temperature-dependent properties due to the thermal-quenching channel generated by the intervalence charge transfer (IVCT) state between Pr3+ and Zr4+ ions. Furthermore, a self-calibrated temperature feedback window with the same fluorescence intensity ratio (FIR) model (I613/I503, where I represents the intensity) under different excitation light sources (295 and 450 nm) is designed. The developed photothermal window operated in a wide temperature range (303–663 K) shows relatively high sensitivities (absolute sensitivity (Sa) and relative sensitivity (Sr) reach 0.008 K−1 at 663 K and 0.47% K−1 at 363 K, respectively), high repeatability (> 98%), and low temperature uncertainty (δT < 3.2 K). This work presents a paradigm for achieving enhanced PL along with elevated transparency of lanthanide (Ln)-doped ceramics through vacuum re-annealing treatment engineering and demonstrates their promising potential for photothermal window systems.

In this work, we demonstrate the usability of a fully-2D-material based device consisting of MoS2/WSe2 heterojunction encapsulated by hBN and contacted by graphene as temperature sensor for linear temperature measurement at cryogenic temperatures. More precisely, temperatures in the range of 10 K up to 300 K were applied to the device while recording the I-V characteristics. In contrast to the classical expectation, the main current flows through the device when it is reversely biased. We ascribe this to a combination of drift-diffusion and band-to-band tunneling, while for very low temperatures (T $ < $ 100 K), variable-range hopping or trap-assisted tunneling seems dominant. In case of forward bias, the Schottky contact on the WSe2-anode hinders the charge transport in the voltage range of interest. Additionally, we obtained the activation energy of the saturation current in reverse direction in an Arrhenius diagram. Depending on the bias level, it varies between 100 meV and 300 meV, which may be related to the energy barrier caused by interface traps, generation centers between both semiconducting 2D materials, and the band-to-band tunneling. Furthermore, we investigated the temperature-sensor performance by applying a constant current to the device and measuring the voltage drop at different temperatures. In the range of 40 K up to 300 K, the sensitivity of the sensor is $\sim 2$ mV/K, which is comparable to Si devices, while the linearity is still lower $(R^{2}~\sim ~0.94$ ). On the other hand, the demonstrated device consists only of 2D materials and is, thus, substrate independent, very thin, and can potentially be fabricated on a fully flexible substrate in a low-cost process.

A sensitive temperature sensor was demonstrated using boron-doped polarization-maintaining photonic crystal fiber (PM-PCF) as a Sagnac interferometer (SI). This boron-doped PM-PCF combines both the geometric birefringence introduced by the PCF structure design and the stress birefringence introduced by the boron-doped stress-applying parts. However, we found that the stress birefringence dominates the total birefringence of the sensor by numerical analysis. In the experiments, the fabricated sensor exhibited the highest temperature sensitivity of −1.83 nm/°C within the wide temperature range of 28~76 °C. The temperature sensitivity was mainly derived from the stress birefringence of boron-doped PM-PCF SI. These findings provide some support for the designation of high-precision temperature sensors.

In this paper, a temperature sensing scheme with a miniature MZI structure based on the principle of inter-mode interference is proposed. The sensing structure mainly comprises single mode–coreless–multimode–coreless–single mode fibers (SCMCSs), which have been welded together, with different core diameters. The light beam has been expanded after passing through the coreless optical fiber and is then coupled into a multimode optical fiber. Due to the light passing through the cladding and core mode of the multimode optical fiber with different optical paths, a Mach–Zehnder interferometer is formed. Moreover, due to the thermo-optic and thermal expansion effects of optical fibers, the inter-mode interference spectrum of a multimode fiber shifts when the external temperature changes. Through theoretical analysis, it is found that the change in the length of the sensing fiber during temperature detection has less of an effect on the sensitivity of the sensing structure. During the experiment, temperature changes between 20 and 100 °C are measured at sensing fiber lengths of 1.5 cm, 2.0 cm, 2.5 cm, 3.0 cm, 3.5 cm, and 4.0 cm, respectively, and the corresponding sensitivities are 65.98 pm/°C, 72.70 pm/°C, 67.75 pm/°C, 66.63 pm/°C, 74.80 pm/°C, and 72.07 pm/°C, respectively. All the corresponding correlation coefficients are above 0.9965. The experimental results indicate that in the case of a significant change in the length of the sensing fiber, the sensitivity of the sensing structure changes slightly, which is consistent with the theory that the temperature sensitivity is minimally affected by a change in the length of the sensing fiber. Therefore, the effect of the length on sensitivity in a cascade-based fiber structure is well solved. The sensing scheme has an extensive detection range, small size, good linearity, simple structure, low cost, and high sensitivity. It has a good development prospect in some detection-related application fields.

The unique properties of upconversion nanoparticles (UCNPs) are responsible for their diverse applications in photonic materials, medicine, analytics, and energy conversion. In this study, water-soluble rare-earth upconversion nanomaterials emitting green, yellow, and red light under 1550 nm excitation were synthesized. These nanomaterials were then integrated into water-soluble Kevlar nanofibers (KNFs) to fabricate ultra-thin composite films exhibiting favorable mechanical characteristics. The characterization of the products, along with their luminescent, mechanical, and temperature-sensing properties, was examined. The results indicate that the composite material exhibited varying colors based on the doped nanoparticles when subjected to 1550 nm excitation. The composite showed highly sensitive temperature-sensing properties, excellent luminescent characteristics, and superior mechanical strength. This study suggests that KNFs are effective carriers of UCNPs. This study offers a reference for the utilization of rare-earth upconversion in anti-counterfeiting displays, wearable health monitoring, and remote temperature sensing.

Multifunctional sensors have played a crucial role in constructing high-integration electronic networks. Most of the current multifunctional sensors rely on multiple materials to simultaneously detect different physical stimuli. Here, we demonstrate the large piezo-pyroelectric effect in ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals for simultaneous pressure and temperature sensing. The outstanding piezoelectric and pyroelectric properties of PMN-PT result in rapid response speed and high sensitivity, with values of 46 ms and 28.4 nA kPa−1 for pressure sensing, and 1.98 s and 94.66 nC °C−1 for temperature detection, respectively. By leveraging the distinct differences in the response speed of piezoelectric and pyroelectric responses, the piezo-pyroelectric effect of PMN-PT can effectively detect pressure and temperature from mixed-force thermal stimuli, which enables a robotic hand for stimuli classification. With appealing multifunctionality, fast speed, high sensitivity, and compact structure, the proposed self-powered bimodal sensor therefore holds significant potential for high-performance artificial perception.

Fiber Bragg gratings (FBGs) have been extensively used for single-point and multi-point measurements, mostly inscribed in single-mode fibers. However, it is feasible to inscribe FBGs in multimode fibers, which resist bending and can perform discriminative sensing of multiple physical parameters. When using a simple experimental setup to measure the temperature dependence of the dip in the transmission spectrum, significant fluctuations in its spectral power can be observed. Therefore, this study shows that the temperature-dependent spectral power fluctuations in multimode FBGs can be mitigated using a reflectometric configuration with suppressed modal interference, leading to higher-reliability temperature sensing.

The combined effects of temperature (from −80 °C to +80 °C) and 100 kV X-ray exposure (up to 108 kGy(SiO2)) on the physical properties of Brillouin scattering and losses in three differently doped silica-based optical fibers, with varying dopant type and concentration (4 wt%(Ge), 10 wt%(Ge) and 1 wt%(F)), are experimentally studied in this work. The dependencies of Brillouin Frequency Shifts (BFS), Radiation-Induced Attenuation (RIA) levels, Brillouin gain attenuation, Brillouin frequency temperature (CT) and strain (Cε) sensitivity coefficients are studied under X-rays in a wide temperature range [−80 °C; +80 °C]. Brillouin sensing capabilities are investigated using a Brillouin Optical Time Domain Analyzer (BOTDA), and several properties are reported: (i) similar behavior of the Brillouin gain amplitude decrease with the increase in the RIA; (ii) the F-doped and heavily Ge-doped fibers do not exhibit a temperature dependence under radiation for their responses in Brillouin gain losses. Increasing Ge dopant concentration also reduces the irradiation temperature effect on RIA. In addition, Radiation-Induced Brillouin Frequency Shift (RI-BFS) manifests a slightly different behavior for lower temperatures than RIA, presenting an opportunity for a comprehensive understanding of RI-BFS origins. Related temperature and strain sensors are designed for harsh environments over an extended irradiation temperature range, which is useful for a wide range of applications.

Whether GPCRs support the sensing of temperature as well as other chemical and physical modalities is not well understood.Introduction: Extracellular Ca2+ concentration (Ca2+o) modulates core body temperature and the firing rates of temperature-sensitive CNS neurons, and hypocalcemia provokes childhood seizures. However, it is not known whether these phenomena are mediated by Ca2+o-sensing GPCRs, including the calcium-sensing receptor (CaSR). In favor of the hypothesis, CaSRs are expressed in hypothalamic regions that support core temperature regulation, and autosomal dominant hypocalcemia, due to CaSR activating mutations, is associated with childhood seizures.Methods: Herein, we tested whether CaSR-dependent signaling is temperature sensitive using an established model system, CaSR-expressing HEK-293 cells.Results: We found that the frequency of Ca2+o-induced Ca2+i oscillations but not the integrated response was linearly dependent on temperature in a pathophysiologically relevant range. Chimeric receptor analysis showed that the receptor’s C-terminus is required for temperature-dependent modulation and experiments with the PKC inhibitor GF109203X and CaSR mutants T888A and T888M, which eliminate a key phosphorylation site, demonstrated the importance of repetitive phosphorylation and dephosphorylation.Discussion and Conclusion: CaSRs mediate temperature-sensing and the mechanism, dependent upon repetitive phosphorylation and dephosphorylation, suggests that GPCRs more generally contribute to temperature-sensing.

In this work, the transmission characteristic of a single mode fiber-silica capillary-single mode fiber (SMF-Capillary-SMF) structure is modified by introducing liquids inside and outside the silica capillary. The anti-resonant reflecting guidance mechanism in the silica capillary is influenced by the presence of the liquids. By immersing a section of liquid-filled SMF-Capillary-SMF structure into liquids, both the resonant wavelength and transmission intensity are altered due to a liquid-modified resonant condition. Temperature change will lead to the refractive index (RI) variation of liquids, causing the resonant wavelength to shift. Experimental results indicate that the temperature sensitivity is dependent on the RI value of the liquids, and the liquid temperature sensitivity of 2.99 nm/°C is experimentally achieved in the temperature range of 25 °C-60 °C when the liquid RI is 1.39. On the other hand, the transmission intensity at resonant wavelength, which is determined by the reflectivity at the inner and outer surfaces of the ring cladding, can be affected when the RI of the ambient liquid changes. The intensity at resonant wavelength increases as the ambient RI rises, and the RI sensitivity varies from 240 dB/RIU to 60 dB/RIU in the RI range of 1.31 to 1.39. Such a device is simple and easy to fabricate, which can find wide applications in liquid environments like biochemical and pharmacy industries.

Cu2+ is an essential trace element for humans and animals, and the precise detection of Cu2+ can help diagnose many diseases. However, the current Cu2+ detection technology still needs to be improved in terms of the biocompatibility of the material, the penetration of the excitation source, and the detection limit. In this paper, the polyacrylic acid (PAA) capped NaYF4:Yb3+/Er3+@NaYF4 core–shell nanoparticles (NPs) with a particle size of about 22.5 nm is proposed. Under the excitation of 980 nm with strong penetration, the Cu2+ concentration can be detected by the emission intensity of NPs at 520 nm, and the detection limit is 0.018 μM. In addition, this material can also perform temperature detection within 296–373 K with a relative sensitivity of 1.23 % K−1. Therefore, this NPs is a promising multifunctional material that can detect temperature and Cu2+ concentration.

Here, we document a D-type double open-loop channel floor plasmon resonance (SPR) photonic crystal fiber (PCF) for temperature sensing. The grooves are designed on the polished surfaces of the pinnacle and backside of the PCF and covered with a gold (Au) film, and stomata are distributed around the PCF core in a progressive, periodic arrangement. Two air holes between the Au membrane and the PCF core are designed to shape a leakage window, which no longer solely averts the outward diffusion of Y-polarized (Y-POL) core mode energy, but also sets off its coupling with the Au movie from the leakage window. This SPR-PCF sensor uses the temperature-sensitive property of Polydimethylsiloxane (PDMS) to reap the motive of temperature sensing. Our lookup effects point out that these SPR-PCF sensors have a temperature sensitivity of up to 3757 pm/°C when the temperature varies from 5 °C to 45 °C. In addition, the maximum refractive index sensitivity (RIS) of the SPR-PCF sensor is as excessive as 4847 nm/RIU. These proposed SPR-PCF temperature sensors have an easy nanostructure and proper sensing performance, which now not solely improve the overall sensing performance of small-diameter fiber optic temperature sensors, but also have vast application prospects in geo-logical exploration, biological monitoring, and meteorological prediction due to their remarkable RIS and exclusive nanostructure.

Chiral BIC can reach ultrahigh quality factors (Q-factor) based on its asymmetry, with broken mirror symmetries and in-plane inversion. Only by in-plane structural perturbation can chiral quasi-BIC (q-BIC) appear, so it is much more realizable and reasonable for the manufacturers in practical productions and fabrications considering the technology and means that are available. In this paper, we design a new dielectric metasurface employing H-shaped silica meta-atoms in the lattice, which is symmetrical in structure, obtaining chiral BIC with ultrahigh Q-factor (exceeding 105). In this process, we change the length of the limbs of the structure to observe the specific BICs. Previous scholars have focused on near-infrared-wavelength bands, while we concentrate on the terahertz wavelength band (0.8–1 THz). We found that there is more than one BIC, thus realizing multiple BICs in the same structure; all of them exhibit excellent circular dichroism (CD) (the maximum value of CD is up to 0.8127) for reflectance and transmittance, which provides significant and unique guidance for the design of multi-sensors. Meanwhile, we performed temperature sensing with chiral BIC; the sensitivity for temperature sensing can reach 13.5 nm/°C, which exhibits high accuracy in measuring temperature. As a consequence, the result proposed in this study will make some contributions to advanced optical imaging, chiral sensors with high frequency and spectral resolution, optical monitoring of environmental water quality, multiple sensors, temperature sensing, biosensing, substance inspection and ambient monitoring and other relevant optical applications.

Metal-organic frameworks are of great interest to scientists from various fields. This group also includes organic–inorganic hybrids with a perovskite structure. Recently their structural, phonon, and luminescent properties have been paid much attention. However, a new way of characterization of these materials has become luminescence thermometry. Herein, we report the structure, luminescence, and temperature detection ability of formate organic–inorganic perovskite [C(NH2)3]M(HCOO)3 (Mg2+, Mn2+, Zn2+) doped with Cr3+ ions. Crystal field strength (Dq/B) and Racah parameters were determined based on diffuse reflectance spectra. It was shown that Cr3+ ions are positioned in the intermediate crystal field or close to it with a Dq/B range of 2.29–2.41. The co-existence of the spin-forbidden and spin-allowed transitions of Cr3+ ions enable the proposal of an approach for remote readout of the temperature. The relative sensitivity (Sr) can be easily modified by sample composition and Cr3+ ions concentration. The luminescent thermometer based on the 2E/4T2g transitions has the relative sensitivity Sr of 2.08%K−1 at 90 K for [C(NH2)3]Mg(HCOO)3: 1% Cr3+ and decrease to 1.20%K−1 at 100 K and 1.08%K−1 at 90 K for Mn2+ and Zn2+ analogs, respectively.

A novel fluorescent probe (C460@Tb-MOFs) was designed and synthesized by encapsulating the fluorescent dye 7-diethylamino-4-methyl coumarin (C460) into a terbium-based metal–organic framework using a simple ultrasonic impregnation method. It is impressive that this dye-modified metal–organic framework can specifically detect styrene and temperature upon luminescence quenching. The sensing platform of this material exhibits great selectivity, fast response, and good cyclability toward styrene detection. It is worth mentioning that the sensing process undergoes a distinct color change from blue to colorless, providing conditions for the accurate visual detection of styrene liquid and gas. The significant fluorescence quenching mechanism of styrene toward C460@Tb-MOFs is explored in detail. Moreover, the dye-modified metal–organic framework can also achieve temperature sensing from 298 to 498 K with high relative sensitivity at 498 K. The preparation of functionalized MOF composites with fluorescent dyes provides an effective strategy for the construction of sensors for multifunctional applications.

As one of the most critical parameters to evaluate the quality and performance of mobile phones, real-time temperature monitoring of mobile phones’ integrated chips is vital in the electronics industry. Although several different strategies for the measurement of chips’ surface temperature have been proposed in recent years, distributed temperature monitoring with high spatial resolution is still a hot issue with an urgent need to be solved. In this work, a fluorescent film material with photothermal properties containing thermosensitive upconversion nanoparticles (UCNPs) and polydimethylsiloxane (PDMS) is fabricated for the monitoring of the chips’ surface temperature. The presented fluorescent films have thicknesses ranging from 23 to 90 μm and are both flexible and elastic. Using the fluorescence intensity ratio (FIR) technique, the temperature-sensing properties of these fluorescent films are investigated. The maximum sensitivity of the fluorescent film was measured to be 1.43% K−1 at 299 K. By testing the temperature at different positions of the optical film, distributed temperature monitoring with a high spatial resolution down to 10 μm on the chip surface was successfully achieved. It is worth mentioning that the film maintained stable performance even under pull stretching up to 100%. The correctness of the method is verified by taking infrared images of the chip surface with an infrared camera. These results demonstrate that the as-prepared optical film is a promising anti-deformation material for monitoring temperature with high spatial resolution on-chip surfaces.

In this paper, a liquid metal mercury (Hg) based high quality-factor (Q-factor) liquid electromagnetic metamaterial unit, the Hg Fano resonator, is designed for the high-precision temperature sensing application. Such Fano resonance in the Hg-resonator is excited by the microstrip-line coupling and the resonance frequency is sensitive to the background temperature changes. Based on the high Q-factor and the temperature-sensitive features of Hg-Fano resonator, the high-precision temperature sensing performance is discussed and achieved, with numerical and experimental demonstrations. The experimental sensitivity of 11.7 MHz/°C and figure-of-merit (FOM) of 0.4/°C are obtained. The proposed compact Hg-Fano resonator-based sensor can be widely used for the wireless temperature sensing area.

Wound management in Space is an important factor to be considered in future Human Space Exploration. It demands the development of reliable wound monitoring systems that will facilitate the assessment and proper care of wounds in isolated environments, such as Space. One possible system could be developed using liquid crystal films, which have been a promising solution for real-time in-situ temperature monitoring in healthcare, but they are not yet implemented in clinical practice. To progress in the latter, the goal of this study is twofold. First, it provides a full characterization of a sensing element composed of thermotropic liquid crystals arrays embedded between two elastomer layers, and second, it discusses how such a system compares against non-local infrared measurements. The sensing element evaluated here has an operating temperature range of 34–38°C, and a quick response time of approximately 0.25 s. The temperature distribution of surfaces obtained using this system was compared to the one obtained using the infrared thermography, a technique commonly used to measure temperature distributions at the wound site. This comparison was done on a mimicked wound, and results indicate that the proposed sensing element can reproduce the temperature distributions, similar to the ones obtained using infrared imaging. Although there is a long way to go before implementing the liquid crystal sensing element into clinical practice, the results of this work demonstrate that such sensors can be suitable for future wound monitoring systems.

We present an ultra-sensitive Surface Plasmon Resonance-based Photonic Crystal Fiber (SPR-PCF) sensor that can be employed for multipurpose sensing of analyte, temperature, and magnetic field. Our prototype has a trigonal cluster-based strategic pattern of circular air holes inside the fiber and can be easily fabricated using the standard Stack-and-Draw method. Thin layers of gold (Au) and titanium dioxide (TiO2) are used as the plasmonic materials surrounding the PCF. The Finite Element Method (FEM) of the commercial software COMSOL Multiphysics 5.3a is used to estimate the sensor properties. After optimization of different parameters, we recorded a maximum Amplitude Sensitivity (AS) of 7223.62 RIU−1, a maximum wavelength sensitivity (WS) of 28,500 nm/RIU, and a leading figure of merit (FOM) of 914 RIU−1. Our sensor is capable of detecting unknown analytes within the refractive index (RI) range of 1.33 to 1.42 with sensor resolutions of 1.38 × 10−6 (amplitude) and 3.51 × 10−6 RIU (wavelength). Furthermore, it can also detect temperature and magnetic field variations with the corresponding maximum sensitivity of 1.25 nm/°C (1250 pm/°C) and 0.16 nm/Oe (160 pm/Oe). An infinitesimal change in the sensor performance was observed for the ±10% fabrication tolerance analysis. So, it can be concluded that our sensor can significantly contribute to scientific, biomedical, and industrial fields due to its supreme sensing capabilities and versatile features.

Bismuth-halide-based inorganic-organic hybrid materials (Bi-IOHMs) are desirable in luminescence-related applications due to their advantages such as low toxicity and chemical stability. Herein, two Bi-IOHMs of [Bpy][BiCl4(Phen)] (1, Bpy = N-butylpyridinium, Phen = 1,10-phenanthroline) and [PP14][BiCl4(Phen)]·0.25H2O (2, PP14 = N-butyl-N-methylpiperidinium), containing different ionic liquid cations and same anionic units, have been synthesized and characterized. Single-crystal X-ray diffraction reveals that compounds 1 and 2 crystallize in the monoclinic space group of P21/c and P21, respectively. They both possess zero-dimensional ionic structures and exhibit phosphorescence at room temperature upon excitation of UV light (375 nm for 1, 390 nm for 2), with microsecond lifetime (24.13 μs for 1 and 95.37 μs for 2). Hirshfeld surface analysis has been utilized to visually exhibit the different packing motifs and intermolecular interactions in 1 and 2. The variation in ionic liquids makes compound 2 have a more rigid supramolecular structure than 1, resulting in a significant enhancement in photoluminescence quantum yield (PLQY), that is, 0.68% for 1 and 33.24% for 2. In addition, the ratio of the emission intensities for compounds 1 and 2 shows a correlation with temperature. This work provides new insight into luminescence enhancement and temperature sensing applications involving Bi-IOHMs.

Based on the transfer-matrix method, we theoretically explore the transmission and reflection properties of light waves in a one-dimensional defective photonic crystal composed of superconductor (HgBa2Ca2Cu3O8+δ) and semiconductor (GaAs) layers. The whole system is centrosymmetric and can generate a defect transmission peak in the photonic band gap. We study the effect of the temperature on the defect mode. Results obtained show that the defect mode shifts to the lower frequency regions as the value of the environmental temperature increases, and the resonance of the defect mode can be strengthened further as the number of periods increases. In addition, our findings reveal that the central wavelength of the defect mode increases with the increase in the environmental temperature and it presents a nearly linear relationship between the central wavelength of the defect mode and the temperature in cryogenic environments. Therefore, we can use the temperature response of the defect mode to detect the temperature. It is hoped that this study has potential applications for the development of cryogenic sensors with high sensitivity.

Fano resonance effect has potential applications in many nanophotonics devices, Such as switch, sensor, and modulators. To realize double Fano resonance effect, in this paper, we present a novel coupling mechanism in a multi-layer metamaterial structure. The structure consists of periodic TiO2 grating covered with MgF2-TiO2-Ag multilayer with a MgF2 substrate. Results show that one of the two Fano resonance is caused by the interference between a broad Fabry-Perot (FP) mode and a dark waveguide mode (WG), and the other Fano resonance is caused by the asymmetric waveguide mode of the MgF2-TiO2-Ag layer. The effect of structural parameters on transmission is also studied, the field distribution of the proposed nanostructure is presented to illustrate the mechanism. We achieve a refractive index sensitivity of 73.5 nm/RIU, and temperature sensitivity of 0.0915nm/°C, the ultra-narrow transmission bandwidth leads to the high FOM*. The results will pave the way towards the design of double band Fano resonance, which may have potential application in high signal-to-noise ratio measurement, plasmonic modulator and refractive index sensor or temperature sensor.

Polypropylene (PP) remains the primary material for hernia meshes due to its biocompatibility, physical strength and ease of fabrication. However, PP meshes are still subject to complications such as mesh movement and bacterial infection that ultimately lead to mesh failure. This study describes a two-step functionalization of a PP mesh through dopamine-mediated chloro(triphenylphosphine)gold(I)/nanodiamond coatings. The gold compound provided an intrinsic surface with antimicrobial activity to the coatings, whilst the overall improvement in hydrophilicity and roughness allows for efficient adsorption of antibiotics with an aim for eradicating bacteria in the surrounding tissue. The presence of a gold compound on the surface of the mesh enhanced its contrast property, which may provide a surgical application to determine the ease of monitoring the PP mesh location after implantation inside the body to detect possible tears. Photostable negatively charged nitrogen-vacancy centres within the nanodiamonds provides an exciting possibility to optically assess locally elevated temperatures often associated with infection or excessive inflammation. The biocompatibility, antibiotic loading and associated antimicrobial properties of the coated mesh were investigated to show the potential of this new coating for future applications in hernia surgical procedures.

A novel method for ultra-sensitive and ultra-fast temperature sensing has been successfully implemented by cascading Saganc rings to generate the Vernier effect and doing the same dispersive fibers to achieve the optical time-stretching effect. This is different from the traditional point fiber sensor demodulated by optical spectrum analyzer (OSA) whose demodulation speed is usually at the second level. The designed system maps the wavelength domain to the time domain through the dispersive fiber, which can realize the ultra-fast temperature monitoring at the nanosecond level. The cascaded Sagnac ring is composed of polarization maintaining fiber (PMF) which is significantly affected by the thermal-optical coefficient. When the temperature changes, the variation is as high as −6.228 nm/°C, which is 8.5 times higher than the sensitivity based on the single Sagnac ring system. Furthermore, through the optical time stretching scheme, the corresponding response sensitivity is increased from 0.997 ns/°C to 7.333 ns/°C, and the magnification is increased 7.4 times with a response speed of 50 MHz.

High precision temperature measurements are a transversal need in a wide area of physical experiments. Space-borne gravitational wave detectors are a particularly challenging case, requiring both high precision and high stability in temperature measurement. In this contribution, we present a design able to reach 1 μK/Hz in most of the measuring band down to 1 mHz, and reaching 20 μK/Hz at 0.1 mHz. The scheme is based on resistive sensors in a Wheatstone bridge configuration which is AC modulated to minimize the 1/f noise. As a part of our study, we include the design of a test bench able to guarantee the high stability environment required for measurements. We show experimental results characterising both the test bench and the read-out, and discuss potential noise sources that may limit our measurement.

A twin-core sensor with high birefringence employing a photonic crystal fiber (PCF) is presented for simulated temperature measurements based on surface plasmon resonance (SPR). The internal wall of the central hole of the PCF is plated with gold and coated with graphene oxide (Au-GO) to develop an SPR sensing channel. The results of a numerical analysis with COMSOL Multiphysics show that the birefringence of this sensing structure can reach 0.0052. In addition, an average sensitivity of -12.695 nm/ °C can be achieved in the range of 0 °C~80 °C. Compared with uncoated GO sensors and existing sensing units, this sensor shows improved stability, sensitivity and birefringence.

For achieving well-performing optical thermometry, a new type of dual-mode optical thermometer is explored based on the valley-to-peak ratio (VPR) and fluorescence lifetime of Eu3+ emissions in the ZrO2:Eu3+ nanocrystals with sizes down to 10 nm. In the VPR strategy, the intensity ratio between the valley (600 nm) generated by the emission band overlap and the 606 nm peak (5D0→7F2), which is highly temperature sensitive, is employed, giving the maximum relative sensing sensitivity (Sr) of 1.8% K−1 at 293 K and good anti-interference performance. Meanwhile, the 606 nm emission exhibits a temperature-dependent decay lifetime with the highest Sr of 0.33% K−1 at 573 K, which is due to the promoted nonradiative relaxation with temperature. These results provide useful information for constructing high-performance dual-mode optical thermometers, which may further stimulate the development of photosensitive nanomaterials for frontier applications.

Abstract A novel fiber inline Mach-Zehnder interferometer (MZI) is proposed for simultaneous measurement of curvature and temperature. The sensor composes of single mode-multimode-dispersion compensation-multimode-single mode fiber (MMF-DCF-MMF) structure, using the direct fusion technology. The experimental results show curvature sensitivities of −12.82 nm/m−1 and −14.42 nm/m−1 in the range of 0–0.65 m−1 for two resonant dips, as well as temperature sensitivities of 57.6 pm/°C and 74.3 pm/°C within the range of 20 °C–150 °C. In addition, the sensor has unique advantages of easy fabrication, low cost, high fringe visibility of 24dB, and high sensitivity, which shows a good application prospect in dual-parameters of sensing of curvature and temperature.

In this article, a refractive index sensor based on Fano resonance, which is generated by the coupling of a metal–insulator–metal (MIM) waveguide structure and a toroidal cavity with a built-in elliptical ring (TCER) structure, is presented. The finite element method (FEM) was employed to analyze the propagation characteristics of the integral structure. The effects of refractive index and different geometric parameters of the structure on the sensing characteristics were evaluated. The maximum sensitivity was 2220 nm/RIU with a figure of merit (FOM) of 58.7, which is the best performance level that the designed structure could achieve. Moreover, due to its high sensitivity and simple structure, the refractive index sensor can be applied in the field of temperature detection, and its sensitivity is calculated to be 1.187 nm/℃.

We theoretically investigate the temperature-dependent Goos-Hänchen (GH) shifts in a symmetrical graphene-cladding waveguide (SGCW). The GH shifts in SGCW present a quasi-periodic tendency near the resonance angle with the change of temperature, which can mainly be attributed to the temperature dependence of the guiding layer’s thickness, instead of the graphene intraband conductivity and guiding layer’s refractive index. Importantly, tiny temperature fluctuations can cause significant deviations in GH shifts, and the deviations can be efficiently improved by adjusting the Fermi energy. Therefore, we propose a high-sensitivity temperature sensing scheme based on GH shifts in the SGCW, and the maximum sensitivity can reach up to −2.2 × 105 μm/°C. These researches may open avenues for applications of optical temperature sensors.

In this paper, to achieve a high-precision temperature sensing, a modified anapole resonator based on the liquid–metal (Hg) with high Q-factor and large thermal-sensitivity properties is proposed. The high-Q resonance of the designed Hg-anapole resonator is excited by a simple microstrip coupling line with large electromagnetic energy coupling rate. The detailed numerical optimization and experimental demonstration are discussed, and the measured temperature sensitivity of 17.14 MHz/°C and figure-of-merit (FOM) of 0.3/°C are achieved based on the proposed Hg-anapole resonator. This kind of liquid high-Q metamaterial unit can be widely used to realize the high-precision sensing.