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We propose a battery-free temperature monitoring device that can be fitted inside the ear for an accurate body temperature measurement of a subject. The proposed application consists of two primary systems: 1) a battery-free temperature sensing ultra-high-frequency radio frequency identification sensory tag and 2) an auxiliary energy harvesting system, which enhances the sensing device's measurement accuracy and precision. The system can record changes in the localized body temperature of authenticated users with an average latency of 501 ms. The assembly demonstrated a temperature average accuracy of ± 0.14 °C operating at 866 MHz. The system performance demonstrated high stability and repeatability of reported temperature measurements. The device's dimension is a form factor that can easily fit in a front shirt pocket, with a wire tethered earbud temperature sensor. The system is developed to make sensor measurements without requiring a battery for the device. Measurements are made remotely as users pass by checkpoints installed throughout a building. The device is a cost-effective solution for monitoring body temperature in work environments.

The occurrence of bedsores in Ghanaian hospitals, elderly homes or care homes is especially high among patients or people who are incapacitated and cannot move or turn on their own, and who happen to remain in a particular posture for a very long time. Patients in coma, those operated on and for that matter in critical state, and patients confined to wheelchairs are primary examples. Constant pressure on some parts of the body leads to the occurrence of pressure sores or ulcers. This paper seeks to implement a Bedsore Easing System (BeSoSys) that integrate several embedded hardware components, a database and software to reduce the occurrence of bedsores. These embedded hardware components include the Bed Device Unit (BDU), the Pocket Device Unit (PDU), a pressure or weight sensor, a temperature sensor, and an inflation-deflation device. The BDU is fitted into the bed of the patient or on the surface of skin contact of the patient. The PDU is assigned to nurses or caretakers to serve as an alarm system for patient repositioning depending on situation. All activities in the Bedsore Easing System are logged into a database for future references. A bedridden patient exerts constant pressure on the bony protrusions of the body, and this causes bedsores. It was found out during the research that in Ghana, the nurses or caretakers used to turn and massage patients at some random time intervals as a way of preventing bedsores. This traditional way of turning and massaging patients is not only tedious but also ineffective. This paper seeks to provide easy, better, and effective solution to ease bedsores. The BeSoSys intends to prevent the occurrence of bedsores hence the alleviation of bedsore complications

Single mode lasers, particularly red-green-blue (RGB) colors, have attracted wide attention due to their potential applications in the photonic field. Here, we realize the RGB single mode lasing in a hybrid two-dimension and three-dimension (2D–3D) hybrid microcavity (μ-cavity) with a low threshold. The hybrid 2D–3D μ-cavity consists of a polymer fiber and a microsphere. Typical RGB polymer film consisting gain materials are cladded on a fiber. To achieve single mode lasing, the polymer fiber therein serves as an excellent gain cavity to provide multiple lasing modes while the microsphere acts as a loss channel to suppress most of the lasing modes. Mode switching can be realized by adjusting the pump position. It can be attributed to the change of coupled efficiency between gain μ-cavity and loss μ-cavity. Our work will provide a platform for the rational design of nanophotonic devices and on-chip communication.

This study proposes a novel twisted and coiled polymer fiber (TCPF) actuator fabricated from a polymer-coated optical fiber. The TCPF actuator is a soft actuator that is driven by heating; the TCPF actuator in combination with a cooling system has been widely studied for applications in robotics. Sensing is a major issue in such units; in particular, temperature sensing is important for the safe usage of the TCPF. To achieve this, the electrical properties of the heating wire are typically utilized. However, this method is affected by the input voltage noise because the circuit used for actuation is the same as that used for sensing. To separate these circuits, this study developed a temperature-sensing method for the TCPF based on an optical fiber. For propagating only the heat of the polymer to the optical fiber, we embedded the optical fiber in the TCPF. This study experimentally demonstrated that the TCPF actuator fabricated using the polymer-coated optical fiber can be driven by heating. Furthermore, using the developed sensing method, we achieved temperature and force control under isometric conditions.

A simply fabricated, highly sensitive, and inexpensive optical fiber temperature sensor is reported with a Fabry–Perot (FP) microcavity of controlled length. The microcavity with controllable length is fabricated by single-mode fiber (SMF) and polydimethylsiloxane (PDMS) for temperature sensing. After the PDMS is cured, the SMF is connected to the supercontinuum light source (SCLS) and the optical spectrometer analyzer (OSA) for online observation of the reflection spectrum. The micro-displacement platform is used to pull the SMF to form an air cavity. After the air cavity is stabilized, ultraviolet (UV) activated glue is used for packaging outside the PDMS. The FP microcavity is formed by the end face of the SMF and the face of PDMS. The length of the FP microcavity can be controlled online by the micro-displacement platform to a minimum of 15 µm. The free spectral range (FSR) may reach 74.8 nm and the interference fringe contrast (IFC) is up to 19.8 dB to allow sensitive measurements across a wide temperature range. The experiments demonstrate a high temperature sensitivity of 5.388 nm/°C from 33 to 93 °C with high repeatability and linearity (R2=0.9937). Stability experiments showed that the maximum changes in wavelength and intensity are only 45 pm and 0.035 dB, respectively. It is anticipated that the easily constructed, compact, and inexpensive fiber-optic temperature sensor will be employed in practical applications.

YGdO3:Er3+ nanoparticles were successfully synthesized by pulsed laser ablation in liquid method. The structural and morphological properties of the product are investigated by X-Ray diffraction and transmission electron microscopy. The upconversion photoluminescence properties were investigated in detail. Obvious stark splitting phenomena were observed in the green and red emission bands. The decay behaviors of three emission bands were studied. Based on thermal coupled energy level related upconversion fluorescence intensity ratio, the temperature sensing properties of product were studied. Linear function has beenused to reveal the relationship between fluorescence intensity ratio and temperature. Using stark sublevels related emission bands, sensitivity of the temperature sensor was successfully enhanced. These results suggest the YGdO3:Er3+ nanoparticles prepared via pulsed laser ablation in liquid are promising luminescent materials for optical thermometry.

Er3+/Yb3+ co-doped InNbO4 phosphors were synthesized using solid state reaction method. Crystal structure was characterized using X-ray diffraction (XRD), which confirm all obtained phosphors had a monoclinic-wolframite structure and no impurity phase was introduced upon doping. Upon 980 nm excitation, upconversion (UC) emission from Er3+ ions was observed in green and red range. UC emission was obviously enhanced after co-doping Yb3+ ions and reached the maximum for 10 mol% Yb3+ ions. The relation between emission intensity and pump power was performed, revealing that the UC emission result from two-photon processes. Optical temperature sensing property was investigated by exploiting fluorescence intensity ratio (FIR) between 2H11/2 and 4S3/2 levels of Er3+ ions. Its maximum value of absolute sensitivity obtained was 0.0091 K-1, suggesting InNbO4:Er3+/Yb3+ phosphors show potential application in optical thermometry.

The urgent requirement of monitoring air pollution worldwide evokes intensive research interest in developing chemiresistive gas sensing techniques. To overcome the limits in sensitivity and selectivity of room temperature (RT) chemiresistive sensing materials, a new strategy using single-atom catalysts (SACs) via surface coordination is proposed. As a proof-of-concept, single Pd atoms on TiO2 (Pd1-TiO2) possess high efficiency in generating adsorbed O2- as well as high activity and selectivity in catalyzing CO oxidation at RT. As a result, Pd1-TiO2 shows record high sensitivity among the reported RT sensing materials, which is even comparable to those of the best materials working at high temperature. It also provides an approximately 1 order of magnitude lower limit of detection than the best CO sensing materials. Moreover, Pd1-TiO2 presents high selectivity toward 12 kinds of interference gases. This work not only paves a way to design high-performance RT gas sensing materials but also extends the application of SACs.

Contactless optical thermometry is successfully applied for accurate local temperature sensing in many scientific and technological areas. The majority of optical thermometers utilize a ratiometric...

The need to sense and track in real time through sustainable and multifunctional labels is exacerbated by the COVID-19 pandemic, where the simultaneous measurement of body temperature and the fast tracking of people is required. One of the big challenges is to develop effective low-cost systems that can promote healthcare provision everywhere and for that, smarter and personalized Internet of things (IoT) devices are a pathway in large exploration, toward cost reduction and sustainability. Using the concept of color-multiplexed quick response (QR) codes, customized smart labels formed by two independent layers and smart location patterns provide simultaneous tracking and multiple synchronous temperature reading with maximum sensitivity values of 8.5% K−1 in the physiological temperature range, overwhelming the state-of-the-art optical sensor for healthcare services provided electronically via the internet (eHealth) and mobile sensors (mHealth). published

The distributed temperature sensing (DTS) system is useful for detecting its surrounding temperature. The fiber optic DTS system offers a number of unique features for which it find useful in a num...

A probe-shaped sensor for simultaneous temperature and pressure measurement was reported in this article. The effective length of the sensor was ∼2mm, consisting of a fiber Bragg grating (FBG) and a Fabry-Perot interferometer (FPI) with a nano silica diaphragm. The response sensitivities of the sensor for pressure and temperature were measured as −0.98 nm/MPa and 11.10 pm/°C, respectively. This sensor had an extremely low cross-sensitivity between pressure and temperature, which provided a significant potential in dual-parameter sensing.

In this study, silver (Ag) island modified up-conversion nano-particle (NaGdF4:Yb3+/Tm3+) thin films were prepared via electrostatic layer by layer (LBL) and spin coating techniques. The spectroscopic results indicated that adding Ag nanoparticles could significantly enhance the up-conversion emission of NaGdF4:Yb3+/Tm3+ thin films at 452 nm and 476 nm. The maximum enhancement factor of ∼15.6 was reached at 476 nm. Furthermore, we prepared microfibers from upconverting nanoparticles solution, the application of microfibers as active and passive waveguides was analyzed by observing the performance of microfibers with and without Ag under 980 nm excitation of the laser source. The fluorescence intensity ratio (FIR) method was adopted to evaluate microfiber sensitivity. The intensity-based temperature sensitivity of blue emission from a single microfiber containing up-conversion nanomaterials (NaGdF4:Yb3+/Tm3+) and Ag nanoparticles reached up to 0.018 K−1 at 310 K compared to 0.0029 K−1 in Ag-free microfiber. Our results suggest that the novel material can be used to construct new nano-thermometers, useful both in biological experiments as well as industrial research.

Precise, sensitive, and reversible thermochromic luminescent sensing can be achieved by PEAMnBrxI3−x (x = 0/1/2/3). Their luminescence ratios of green to red exhibited a reversible linear response to the temperature increment process (from 40 °C to 120 °C), bright luminescence under high temperature, and reversible heating–cooling circulation performance. Based on the thermochromic luminescence properties, the PEAMnBr2I–polymer film was used for precise and real-time temperature sensing. A deep understanding of their thermochromic luminescence mechanism can facilitate the design of thermochromic materials with high performance and their wider applications.

Temperature is one of the physical parameters that affects the emission luminescence properties of upconversion (UC) materials. Temperature-dependent emission color tuning and good temperature sensitivity in multifunctional β-NaYF4:Yb/Er@β-NaYF4:Yb/Tm microcrystals were achieved under 980 nm excitation. Based on the different emission bands (blue, green and red bands) and spectral sensitivities of the core–shell structured microcrystals to temperature, intense white-light emission was obtained at room temperature and a real-time naked-eye recognizable emission color change from white to the purplish-pink region was realized with the temperature increasing from 300 to 500 K. Furthermore, optical temperature sensing properties of the sample with good sensitivity (from 0.0034 to 0.0044 K−1) were investigated by using a fluorescence intensity ratio between 521 nm (2H11/2 → 4I15/2 transition) and 540 nm (4S3/2 → 4I15/2 transition) in the temperature range from 300 to 500 K. The results indicate that the sample has high sensitivity in a relatively wide range of temperature intervals, especially in the low temperature region. We believe that the multifunctional core–shell structured microcrystals exhibit promising applications in white-light emitting diodes, the anti-counterfeiting field, and temperature sensing.

In this paper, we demonstrate that nitride-based R/G/B micro-LEDs allow temperature sensing through a forward voltage response on both temperature and display devices. In temperature sensing, micro...

Realizing multicolored luminescence in two-dimensional (2D) nanomaterials would afford potential for a range of next-generation nanoscale optoelectronic devices. Moreover, combining fine structured spectral line emission and detection may further enrich the studies and applications of functional nanomaterials. Herein, a lanthanide doping strategy has been utilized for the synthesis of 2D ZnSe:Er

We present the first report on reflectometric optical fiber sensing based on mechanically induced cascaded long-period grating (LPG) structure. This method utilizes in-house designed mechanical casings and a bare fiber. When a fiber is sandwiched between the casings and pressed by tightening screws, an LPG is induced due to a photo-elastic effect. By exploiting Fresnel refection at a fiber end, a cascaded LPG structure can be implemented using a single LPG, enabling reflectometric configuration. When this sensor is subjected to external physical processes, the attenuation bands change clearly, and their shift can be used for non-destructive evaluations. We show experimentally that this sensor can measure loads of up to 10 N without producing any permanent change in the fiber properties, indicating its pressure sensing capability. We also show that this sensor can potentially measure strain and temperature. In our experiments, the strain and temperature sensitivities are 9.4 nm/% and 0.045 nm/°C, respectively.

Flexible coatings with dual capabilities for remote real-time temperature sensing and photothermal conversion have a huge potential in the field of advanced thermal actuated optoelectronic applicat...

A series of garnet-structured Li6Ca(La0.99-xYbxEr0.01)2Nb2O12 (0≤x≤0.05) phosphors were originally synthesized and examined for upconversion (UC) luminescence and optical temperature sensing under 978 nm laser excitation. It was identified that the optimal content of Yb3+ sensitizer is x=0.04 for Er3+ emission and the non-thermally coupled 2H11/2/4F9/2 energy levels of Er3+ possess a superior capability of optical thermometry, whose maximum absolute sensitivity (~15.20 × 10−3 K−1 at 523 K) is generally ~1.7-6.1 times the values reported to date for most of other UC systems.

Background With the aim of addressing the difficulty in identifying temperatures in virtual chemistry experiments, we propose a temperature-sensing simulation method of virtual chemistry experiments. Methods We construct a virtual chemistry experiment temperature simulation platform, based on which a wearable temperature generation device is developed. The typical middle school virtual experiments of concentrated sulfuric acid dilution and ammonium nitrate dissolution are conducted to verify the actual effect of the device. Results The platform is capable to indicate near real-world experimental situations. The performance of the device not only meets the temperature sensing characteristics of human skin, but also matches the temperature change of virtual chemistry experiments in real-time. Conclusions It is demonstrated that this temperature-sensing simulation method can represent exothermic or endothermic chemistry experiments, which is beneficial for students to gain understanding of the principles of thermal energy transformation in chemical reactions, thus avoiding the danger that may be posed in the course of traditional teaching of chemistry experiments effectively. Although this methoddoes not have a convenient enough operation for users, the immersion of virtual chemical experiments can be enhanced.

In this paper, BaY2O4:Yb3+/Er3+, a high efficient red upconversion (UC) material, is first utilized as an optical thermometer in the biological window, accomplished through the fluorescence intensity ratio (FIR) of thermally coupled Stark sublevels of 4F9/2 (FIR(654/663)). The maximum absolute sensitivity of FIR(654/663)) is 0.19% K-1 at 298 K, which is much higher than most previous reports about FIR-based temperature sensors located in the biological windows. More importantly, the groove of FIR(654/663) for thermometry is nicely located in the physiological temperature range, indicating its potential thermometry application value in biomedicine. Furthermore, a simply ex vivo experiment is implemented to evaluate the penetration depth of the red emission in biological tissues, revealing that a detection depth of 6 mm can be achieved without any effect on the FIR values of I654 to I663. Beyond that, the temperature sensing behaviors of the thermally coupled levels 2H11/2 and 4S3/2 (FIR(523/550)) are also investigated in detail. In the studied temperature range, the absolute sensitivity of FIR(523/550) monotonously increases with the rising temperature and reaches its maximum value 0.31% K-1 at 573 K. All the results imply that BaY2O4:Yb3+/Er3+ is a promising candidate for deep-tissue optical thermometry with high sensitivity.

A temperature sensor with high sensitivity based on the birefringence induced Vernier effect in a symmetrical metal-cladding waveguide (SMCW) structure is theoretically proposed. Due to the guiding...

In this paper, upcovnerison luminescence in Er3+/Yb3+ co-doped NaYF4 nanophosphors was regulated by changing the Er3+ concentration. With increasing the Er3+ concentration, the green and red emissions increased first and then decreased, but the intensity ratio of red to green emission decreased monotonically. To clarify the role of Er3+ doping, the factors including crystal structure, morphology and size of particle, photon absorption, energy transfer, multi-phonon relaxation, population of emissive levels and emission probability of radiative transitions were considered and analyzed. More importantly, we proposed a simple method for discussing radiation transitions based on luminescence temperature sensing.

This study developed a vest prototype capable of monitoring body temperature using textile electrodes to prevent the sudden death of babies as well as to determine the quality of developed products by evaluating usability with commercial products. Based on the results of the 7th Size Korea Project, a basic pattern for a vest prototype was drafted by applying the average size of two-year-old Korean babies. Two prototypes were the detachable (VEST I) and integrated textile electrodes vest type (VEST II), which followed the same design. The materials were 100% cotton single jersey (SJ) and double jersey (DJ). Six experts evaluated the usability of the developed vests (VEST I & VEST II) and commercial product (VEST M). The single-layer woven textile electrode appeared to have a slightly higher conductivity than the double-layer one. There was no statistical difference in the body temperature sensing function between VEST I and VEST II. Finally, the superiority of the VEST I was verified through a comparison with commercial products (VEST M). The usability test suggested that a wearable smart clothing system of the integrated conductive textile could be further commercialized for bio-monitor applications in Ubiquitous-health care.

Lanthanide ion doped upconversion nanomaterials have attracted great interest because of their extensive application, especially in color display and temperature sensing. However, control synthesis...

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.