Temperature-sensing Performance Research Articles

Optical Temperature-Sensing Performance of La2Ce2O7:Ho3+ Yb3+ Powders.

In this paper, La2Ce2O7 powders co-activated by Ho3+ and Yb3+ were synthesized by a high temperature solid-state reaction. Both Ho3+ and Yb3+ substitute the La3+ sites in the La2Ce2O7 lattice, where the Ho3+ concentration is 0.5 at.% and the Yb3+ concentration varies in the range of 10~18% at.%. Pumped by a 980 nm laser, the up-conversion (UC) green emission peak at 547 nm and the red emission at 661 nm were detected. When the doping concentration of Ho3+ and Yb3+ are 0.5 at.% and 14% at.%, respectively, the UC emission reaches the strongest intensity. The temperature-sensing performance of La2Ce2O7:Ho3+ with Yb3+ was studied in the temperature range of 303-483 K, where the highest relative sensitivity (Sr) is 0.0129 K-1 at 483 K. The results show that the powder La2Ce2O7:Ho3+, Yb3+ can be a potential candidate for remote temperature sensors.

Development and application of temperature-sensing underwear for breast monitoring

Purpose Breast cancer has become the largest cancer in the world today. Health problems for women with breast cancer need to be addressed urgently. This study aims to select the best method for preparing temperature-sensitive sports underwear, and to verify the feasibility of using K-type thermocouple threads in underwear fabrics.Design/methodology/approach In the experiments, two samples were designed for temperature-sensitive performance tests and the effects produced by different outer layer structures were investigated. In the second step, K-type thermocouple wires were integrated into sports underwear. The comfort and feasibility of the temperature-sensitive underwear were investigated.Findings It was finally verified to obtain the best comfort and temperature-sensing performance of K-type thermocouple filaments integrated into sports underwear with plain stitching.Originality/value The underwear has a certain prospect for the application of smart apparel based on breast cancer health monitoring, which is of some significance for monitoring smart apparel.

Flexible temperature-pressure dual sensor based on 3D spiral thermoelectric Bi2Te3 films

Dual-parameter pressure-temperature sensors are widely employed in personal health monitoring and robots to detect external signals. Herein, we develop a flexible composite dual-parameter pressure-temperature sensor based on three-dimensional (3D) spiral thermoelectric Bi2Te3 films. The film has a (000l) texture and good flexibility, exhibiting a maximum Seebeck coefficient of −181 μV K–1 and piezoresistance gauge factor of approximately −9.2. The device demonstrates a record-high temperature-sensing performance with a high sensing sensitivity (−426.4 μV K−1) and rapid response time (~0.95 s), which are better than those observed in most previous studies. In addition, owing to the piezoresistive effect in the Bi2Te3 film, the 3D-spiral deviceexhibits significant pressure-response properties with a pressure-sensing sensitivity of 120 Pa–1. This innovative approach achieves high-performance dual-parameter sensing using one kind of material with high flexibility, providing insight into the design and fabrication of many applications, such as e-skin.

Wearable and Recyclable Water-Toleration Sensor Derived from Lipoic Acid.

Flexible wearable sensors recently have made significant progress in human motion detection and health monitoring. However, most sensors still face challenges in terms of single detection targets, single application environments, and non-recyclability. Lipoic acid (LA) shows a great application prospect in soft materials due to its unique properties. Herein, ionic conducting elastomers (ICEs) based on polymerizable deep eutectic solvents consisting of LA and choline chloride are prepared. In addition to the good mechanical strength, high transparency, ionic conductivity, and self-healing efficiency, the ICEs exhibit swelling-strengthening behavior and enhanced adhesion strength in underwater environments due to the moisture-induced association of poly(LA) hydrophobic chains, thus making it possible for underwater sensing applications, such as underwater communication. As a strain sensor, it exhibits highly sensitive strain response with repeatability and durability, enabling the monitoring of both large and fine human motions, including joint movements, facial expressions, and pulse waves. Furthermore, due to the enhancement of ion mobility at higher temperatures, it also possesses excellent temperature-sensing performance. Notably, the ICEs can be fully recycled and reused as a new strain/temperature sensor through heating. This study provides a novel strategy for enhancing the mechanical strength of poly(LA) and the fabrication of multifunctional sensors.

The Interconnecting Process and Sensing Performance of Stretchable Hybrid Electronic Yarn for Body Temperature Monitoring.

Flexible and stretchable electronic yarn containing electronic components (i.e., hybrid electronic yarn) are essential for manufacturing smart textile garments or fabrics. Due to their low stretchability and easy interconnection fracture, previously reported hybrid electronic sensing yarns have poor mechanical durability and washability. In order to address this issue, a stretchable hybrid electronic yarn for body temperature monitoring was designed and prepared using a spandex filament as the core yarn and a thin enameled copper wire connected with a thermal resistor as the wrapping fiber. The temperature sensing performance of different hybrid electronic yarn samples was evaluated using the following three types of interconnection methods: conductive adhesive bonding, melt soldering, and hot pressure bonding. The optimal interconnection method with good sensing performance was determined. Furthermore, in order to improve the mechanical durability of the hybrid electronic yarn made using the optimal interconnection method, the interconnection area was encapsulated with polymers, and the effect of polymer materials and structures on the temperature-sensing properties was evaluated. The results show that traditional wrapping combined with hot pressing interconnection followed by tube encapsulating technology is beneficial for achieving high stretchability and good temperature-sensing performance of hybrid electronic yarn.

Optical temperature-sensing properties of trivalent europium with high sensitivities in a wide temperature range

To develop new luminescent materials for optical thermometer, the Eu3+-activated BaY2ZnO5 (BYZ) phosphors were designed. Upon 394 nm excitation, several groups of 5D0-2→7FJ (J = 0–4) transitions are observed, and the dominant emission is located at 625 nm. The temperature-dependent emission spectra reveal that the emission peaks are weakened with different rates, depending on the excited states of Eu3+. The transient decay kinetics, studied at various temperatures, are in agreement with the emission spectral features. The optical temperature-sensing performance is evaluated with two strategies. For the thermally-coupled (TC) levels of Eu3+, the fluorescence intensity ratio (FIR) of the 536 and 593 nm emissions follows the Boltzmann distribution, and the sensor sensitivities rise with increasing temperature. For the non-TC levels of 5D0 and 5D2, the piecewise functions between the FIRs and absolute temperature are utilized, and the highest absolute and relative sensitivities in the BYZ:7%Eu3+ phosphor are obtained to be 0.674 and 2.19% K−1 at 533 K, respectively. Thus, the developed samples can show higher sensitivities at higher temperature.

High-performance dual-tunable terahertz absorber based on strontium titanate and bulk Dirac semimetal for temperature sensing andswitching function.

In this study, a perfect metamaterial absorber based on strontium titanate and bulk Dirac semimetals is proposed. When the temperature of strontium titanate was 300K, the dual-band absorptions were 99.74% and 99.99% at 1.227 and 1.552THz, respectively. The sensitivities based on a transverse magnetic (TM) wave were 0.95 and 1.22GHz/K; the sensitivity based on a transverse electric (TE) wave was 0.76GHz/K. The TE and TM waves were modulated by inserting a bulk Dirac semimetal between the concave and convex devices. The modulation depth of the TE wave was 97.9% at 1.1THz; the extinction ratio was 16.9dB. The modulation depth of the TE wave at 1.435THz was 95.9%; the extinction ratio was 13.89dB. The TM wave modulation depth at 1.552THz was 95.9%; the extinction ratio was 13.98dB. Irrespective of a TE or TM wave, the terahertz absorber has good switching and temperature-sensing performance based on strontium titanate and bulk Dirac semimetals as well as broad application prospects in temperature sensing and switching devices.

Studies on the Platinum Thick Film Sensor Conformally Written by Laser Micro-Cladding: Formability, Microstructure, and Performance

In this paper, laser micro-cladding technology (LMC) was conducted to prepare high-temperature Pt thick film sensors in situ. The formability, microstructure, sintering mechanism, and electrical properties of the LMCed Pt thick films were first studied systematically. Results indicated that with the increase of laser power density, the sintering degree of the Pt thick film increased obviously, improving its adhesion strength and reducing its resistivity. However, when the laser power density exceeded the threshold, holes or grooves were formed in the Pt film, leading to the degeneration of its properties. A Pt thick film with good adhesion strength, excellent conductive networks, and the minimum resistivity (46 ± 2 μΩ·cm) was obtained at a laser power density of 1.37 × 106 W·cm-2. Then, Pt thick film temperature sensors (including Pt thermal resistance temperature (RTD) and Pt-Pt10%Rh thermocouple sensors) were conformally prepared by LMC. Their temperature-sensing performance became stable after the initial high-temperature calibration, with a linearity of 0.9985 for the RTD with a TCR of 2.46 × 10-3/°C (at 920 °C) and a linearity of 0.9905 for the thermocouple with a Seebeck coefficient of 9.7 μV/°C, both of which are better than that made by direct DC magnetron sputtering deposition. Therefore, this work provides a novel feasible way to conformally integrate high-performance Pt film sensors in situ.

Dual-driven ratiometric luminescence behaviour of Eu2+ and Eu3+ in a single host of SrAl2O4 prepared in ambient atmosphere

Eu2+/Eu3+ co-activated luminescence as a key technology has gradually attracted attention in many research and application fields, including solid-state lighting, printing and dyeing, temperature sensing, etc. Here, by virtue of the unique self-reduction characteristics of Eu3+ in certain host lattices, Eu2+/Eu3+ co-activated luminescent material of SrAl2O4:Eu2+/3+ with single host lattice was prepared by solid-state reaction in the ambient atmosphere. The phase composition and crystal structure were determined by X-ray powder diffraction and Rietveld refinement. The micromorphology was observed by scanning electron microscope and transmission electron microscope. From the perspective of applied science, the dual-driven luminescence behavior and temperature-sensing properties of the material were studied and discussed. The ratiometric luminescence of Eu2+ and Eu3+ in SrAl2O4 can be regulated by the excitation wavelength from ultraviolet to visible light. The luminescent material shows temperature-sensing performance superior to other similar Eu2+/Eu3+ co-activated luminescent materials, with absolute sensitivity of 0.067 K−1 and relative sensitivity of 1.6% K−1. The development of this luminescent material provides a unique insight for designing novel Eu2+/Eu3+ co-activated luminescent materials for multifunctional applications.

Refractive Index and Temperature Sensing Performance of Microfiber Modified by UV Glue Distributed Nanoparticles.

Dielectric materials with high refractive index have been widely studied to develop novel photonic devices for modulating optical signals. In this paper, the microfibers were modified by silicon nanoparticles (NPs) and silver NPs mixed in UV glue with ultra-low refractive index, respectively, whose corresponding optical and sensing properties have been studied and compared. The influence from either the morphological parameters of microfiber or the concentration of NPs on the refractive index sensing performance of microfiber has been investigated. The refractive index sensitivities for the microfiber tapers elaborated with silver NPs and silicon NPs were experimentally demonstrated to be 1382.3 nm/RIU and 1769.7 nm/RIU, respectively. Furthermore, the proposed microfiber was encapsulated in one cut of capillary to develop a miniature temperature probe, whose sensitivity was determined as 2.08 nm/°C, ranging from 28 °C to 43 °C.

Enhanced Upconversion Luminescence and Temperature Sensing Performance in Er3+/Yb3+ -Codoped K3scf6 Phosphors Induced by Tridoping with Bi3+ Ions

Enhanced Upconversion Luminescence and Temperature Sensing Performance in Er3+/Yb3+ -Codoped K3scf6 Phosphors Induced by Tridoping with Bi3+ Ions

Circular Radio-Frequency Electrode With MEMS Temperature Sensors for Laparoscopic Renal Sympathetic Denervation.

Laparoscopic renal denervation (LRDN) ablates sympathetic nerves on the outer wall of a renal artery to treat autonomic nervous system disorders such as hypertension and arrhythmia. Here, we developed a new circular radio frequency (RF) electrode for LRDN using micro-electro-mechanical systems (MEMS) technology. The electrode consists of a parallel bipolar MEMS electrode, two MEMS thermocouples, and a shape-memory alloy (SMA) substrate. The electrode is automatically wrapped and unwrapped under actuation controlled by the heat generated by RF energy on the electrode-tissue interface. The electrode was designed through a computational simulation analysis, and its actuation and temperature-sensing performance were tested in laboratory experiments and a porcine animal study. In an in-vivo study of porcine renal arteries, the electrode could automatically wrap and unwrap around an artery during LRDN. The bipolar MEMS electrode required 13 Vrms for heat generation up to 60°C, while the two MEMS thermocouples reliably measured the temperature without noise signals (a temperature coefficient of 38.3 or 38.5 µV/°C and an accuracy of ±0.44 or ±0.49°C). As revealed in a histological analysis using hematoxylin and eosin staining and Masson's trichrome staining, the renal artery was intact after LRDN. The circular RF electrode improves the safety of LRDN by reliably measuring the electrode temperature of the electrode during RDN and enhances the effectiveness of LRDN by reducing the complicated manipulations of the surgical instrument. The developed circular RF electrode will pave the way for LRDN treatment of autonomic nervous system disorders.

Improving the temperature-sensing performance of the SrZn0.33Nb0.67O3:Pr3+ phosphor via Ga3+ doping

This work highlights a novel optical thermometric phosphor SrZn0.33Nb0.67O3:Pr3+ as well as its remarkably improved temperature-sensing performance via Ga3+ doping.

Flexible and Transparent Pressure/Temperature Sensors Based on Ionogels with Bioinspired Interlocked Microstructures.

Bioinspired by the interlocked geometry between the epidermal-dermal layers of natural skin, here we design a flexible and transparent (94.2%) skin-like sensor with an interlocked hexagonal microcolumn array structure based on ionogels of ionic liquids (ILs) and thermoplastic polyurethane (TPU) assisted by laser-etched silicon wafers. Attributed to the bioinspired microstructure, the resulting interlocked TPU@IL ionogel sensor exhibits outstanding pressure-sensing properties, which has an ultralow detection limit (∼10 Pa) and ultrafast responsiveness (∼24 ms). Interestingly, it is worth noting that the interlocked TPU@IL ionogel sensor also has high temperature-sensing performance because of the dependence of the ionic conductivity of ILs on the temperature, which can accurately detect a slight temperature change (0.1 °C). Moreover, the interlocked TPU@IL ionogel sensor can also serve as the strain sensor in the strain range of 0.1-10%. Attributed to the intrinsically antibacterial effect of ILs, the interlocked TPU@IL ionogel sensor possesses an antibacterial function, which is a desired merit of wearable electronics and devices. The current study provides a novel strategy to manufacture transparent, flexible, and antimicrobial e-skin sensors with multiple sensing capabilities, which may inspire more future research studies for e-skins.

Paper-Based Ionic Thermocouples for Inexpensive and High-Precision Measurement of Temperature.

Accurate and yet cost-effective temperature measurements are required in various sectors of academia and industry. Thermocouples (TCs) are most widely used for temperature measurements; however, their low temperature sensitivity and high thermal conductivity should be improved to ensure the reliable measurement of output voltage for small temperature differences. To address this, a paper-based ionic thermocouple (P-iTC) presented here utilizes a pair of paper strips soaked with the electrolytes of potassium ferri-/ferrocyanide and iron (II/III) chloride redox couples, which are used as p- and n-type elements, respectively. The fabricated P-iTC provides 70× higher temperature sensitivity (α, 2.8 mV/K) and 30× lower thermal conductivity (k, 0.8 W/m K) than those of commercial K-type TCs, thereby yielding a remarkably high α/k ratio of 3.5 mV m/W. Reliable sensing performance is measured during three weeks of operation, which indicates that the P-iTC should be stable in long-term operation. To demonstrate the practicality of the P-iTC, a 3 × 3 planar array of P-iTCs is fabricated to monitor the temperature profile of a surface in contact with heat sources. Using pencil-drawn graphite electrodes on paper, a highly cost-effective P-iTC with the material cost of ∼0.5 cents per device is also fabricated, which is successfully used to monitor cold chain temperatures while retaining its excellent temperature-sensing performance.

Excellent multi-color emission and multi-mode optical ratiometric thermometer in (Ca, Tb, Eu, Sm)Nb2O6 phosphors based on wide O2–→Nb5+ CTB

To meet the demand of ultra-sensitive and high accurate temperature measurements especially in the fields of medical treatment and diagnosis, multi-mode FIR-based optical thermometers as a novel strategy have been developed in recent years. In this work, two types of temperature probes, CaNb2O6 (CNO): Tb3+, Eu3+ and CNO: Tb3+, Sm3+, are firstly designed by high-temperature solid-state method. CNO possesses bright cyan emission excited at 267 nm, wide band gap and good temperature sensing property relative to BaNb2O6 (BNO) and SrNb2O6 (SNO) materials due to sandwich-type structure. Upon 267 nm excitation, Tb3+–Eu3+/Sm3+ doped CNO phosphors achieve multi-color tuning by host → Tb3+→Eu3+/Sm3+ ET channels. Furthermore, the characteristic emission intensity of Tb3+ decrease quickly than that of Eu3+ and Sm3+ due to the competition between thermal quenching and ET process as temperature rising. In the view of different temperature-dependent behaviors, multi-mode FIR (FIR1: ITb1/IEu1/Sm1, FIR2: ITb2/IEu2/Sm2, FIR3: ITb1/IEu2/Sm2 and FIR4: ITb2/IEu1/Sm1) show excellent temperature-sensing performance with the maximum Sa and Sr of 0.036 K−1/ 4.09 % K−1 at high temperature. This work provides a new luminescent material to gain excellent optical thermometer with low cost and high accuracy by multi-mode FIR collaboration.

Exploration of the Temperature Sensing Ability of La2MgTiO6:Er3+ Double Perovskites Using Thermally Coupled and Uncoupled Energy Levels.

This work aimed to explore the temperature-sensing performance of La2MgTiO6:Er3+ double perovskites based on thermally coupled and uncoupled energy levels. Furthermore, the crystal structure, chemical composition, and morphology of the samples were investigated by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy, respectively. The most intense luminescence was observed for the sample doped with 5% Er3+. The temperature-dependent emission spectra of La2MgTiO6:5% Er3+ were investigated in the wide range of 77–398 K. The highest sensitivity of the sample was equal to 2.98%/K corresponding to the thermally coupled energy level 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 as compared to 1.9%/K, obtained for the uncoupled energy level 2H11/2 → 4I15/2 and 2H9/2 → 4I15/2. Furthermore, the 300 K luminescent decay profiles were analyzed using the Inokuti–Hirayama model. The energy transfer among Er3+ ions was mainly regulated by the dipole–dipole mechanism. The critical transfer distance R0, critical concentration C0, energy transfer parameter Cda, and energy transfer probability Wda were 9.81 Å, ions·cm−3, cm6·s−1, and 6020 s−1, respectively.

Optical temperature-sensing properties based on upconversion luminescence of La9.31Si6.24O26:Er3+,Yb3+ with different strategies

A series of novel La9.31Si6.24O26:Er3+,Yb3+ (LS:Er3+,Yb3+) luminescent materials have been successfully synthesized by conventional solid-state reaction method. The phases, morphologies and upconversion (UC) luminescence properties were systematically researched by XRD, SEM, PL spectra, etc. The optimum Yb3+ concentration in LS:1%Er3+,xYb3+ was determined to be × = 15%, above which the concentration quenching effect appeared due to the increasing energy back transfer from Er3+ to Yb3+. Meanwhile, the FIR technique (by using I522/I554 and I660/I522 of Er3+) was employed to study the temperature-sensing performance. As the rise of temperature for all the different Yb3+ concentrations, the values of the absolute sensitivity SA increased first and then decreased by utilizing I522/I554, but showed continuous decrease by using I660/I522. For the relative sensitivity SR, it has been found that the SR values for all the samples exhibited gradual decrease with rising temperature. Besides, the experiment of the heating–cooling cycles between 283 and 523 K proved that the LS:Er3+,Yb3+ material has good reversibility and repeatability. The above results indicated that the LS:Er3+,Yb3+ may be a potential candidate for optical temperature sensor.

Multilayered Composites with Modulus Gradient for Enhanced Pressure-Temperature Sensing Performance.

Highly sensitive and flexible composite sensors with pressure and temperature sensing abilities are of great importance in human motion monitoring, robotic skins, and automobile seats when checking the boarding status. Several studies have been conducted to improve the temperature-pressure sensitivity; however, they require a complex fabrication process for micro-nanostructures, which are material-dependent. Therefore, there is a need to develop the structural designs to improve the sensing abilities. Herein, we demonstrate a flexible composite with an enhanced pressure and temperature sensing performance. Its structural design consists of a multilayered composite construction with an elastic modulus gradient. Controlled stress concentration and distribution induced by a micropatterned structure between the layers improves its pressure and temperature sensing performance. The proposed composite sensor can monitor a wide range of pressure and temperature stimuli and also has potential applications as an automotive seat sensor for simultaneous human temperature detection and occupant weight sensing.

Ratiometric fluorescence temperature-sensing properties of Eu3+ and Tm3+ in Gd4.67Si3O13 oxide host

A series of Eu3+ and Yb3+-Tm3+ doped Gd4.67Si3O13 (GS) phosphors were designed by using solid-state reaction method, and their photoluminescence properties were studied for optical temperature sensing applications. Single-phase samples were checked from XRD patterns and Rietveld refinement. Strong red emission of Eu3+ was obtained in the GS:Eu3+ phosphors upon 393 nm excitation. By employing the emissions from 5D1 and 5D0 levels of Eu3+, it has been found that the ratio of 535 and 577 nm emission intensities follows a linear relationship with absolute temperature. High sensitivities were obtained in the 5 mol% Eu3+ doped GS phosphor. It is important to find that the relative sensitivity shows a larger value at higher temperature, indicating the phosphor is more suitable to be used at relatively high temperature. By codoping Yb3+ and Tm3+ into the GS host, the upconversion (UC) luminescence of Tm3+ was received. The corresponding UC luminescent features and mechanism were investigated from the decay curves and pump-power-dependent spectra. Two kinds of fluorescence intensity ratio techniques were employed for the optical temperature sensing, i.e., I697/I648 and I697/I789. The high relative sensitivity (SR) and small SR variation interval for I697/I648 reveal good optical temperature-sensing performance. Owing to the large energy gap between 3H4 and 3F3 levels of Tm3+, high SR value can be achieved for I697/I789.