Fast Response Temperature Research Articles

Adjustment of temperature sensitivity using hydrophilic materials to develop superabsorbent polymers based on poly(N‐isopropyl acrylamide) as a temperature‐sensitive material

AbstractPoly(N‐isopropyl acrylamide) (PNIPAm) is a temperature‐sensitive material with a fast temperature response and a low critical solubilization temperature (LCST) of approximately 32°C, but it swells only 20–40 times after absorbing water. To enhance its water‐absorption properties, we introduced hydrophilic monomers into the NIPAm monomer to prepare a ternary copolymerized superabsorbent polymer. In addition, we characterized this copolymer using various techniques and analyzed its temperature‐sensitive and water‐absorbing properties. The results showed that the optimal synthesis conditions consisted of m(NIPAm):m(AMPS) = 4, 1.5% initiator, 0.3% cross‐linking agent, and 1.0% quaternized ammonium chitosan, which ensured the significant temperature sensitivity of the water‐absorbent resin. Under these conditions, the swelling ratio of the water‐absorbing resin reached 235.3 times, the LCST value was 44.6°C, the water retention rate was 84.9% at 25°C after 12 h, and the shrinkage ratio reached 81.7% at 60°C after 3 h, and 97.6% after 12 h. The resulting material could be rapidly dehydrated at high temperatures and presented clear temperature‐sensitive characteristics while maintaining excellent water‐absorbing properties.

Toward Humidity-Independent Sensitive and Fast Response Temperature Sensors Based on Reduced Graphene Oxide/Poly(vinyl alcohol) Nanocomposites.

Flexible temperature sensors are becoming increasingly important these days. In this work, we explore graphene oxide (GO)/poly(vinyl alcohol) (PVA) nanocomposites for potential application in temperature sensors. The influence of the mixing ratio of both materials, the reduction temperature, and passivation on the sensing performance has been investigated. Various spectroscopic techniques revealed the composite structure and atomic composition. These were complemented by semiempirical quantum chemical calculations to investigate rGO and PVA interaction. Scanning electron and atomic force microscopy measurements were carried out to evaluate dispersion and coated film quality. The temperature sensitivity has been evaluated for several composite materials with different compositions in the range from 10 to 80 °C. The results show that a linear temperature behavior can be realized based on rGO/PVA composites with temperature coefficients of resistance (TCR) larger than 1.8% K-1 and a fast response time of 0.3 s with minimal hysteresis. Furthermore, humidity influence has been investigated in the range from 10% to 80%, and a minor effect is shown. Therefore, we can conclude that rGO/PVA composites have a high potential for excellent passivation-free, humidity-independent, sensitive, and fast response temperature sensors for various applications. The GO reduction is tunable, and PVA improves the rGO/PVA sensor performance by increasing the tunneling effect and band gap energy, consequently improving temperature sensitivity. Additionally, PVA exhibits minimal water absorption, reducing the humidity sensitivity. rGO/PVA maintains its temperature sensitivity during and after several mechanical deformations.

Converting bio-waste rice into ultralight hierarchical porous carbon to pack polyethylene glycol for multifunctional applications: Experiment and molecular dynamics simulations

A structural-functional integrated shape-stabilized composite phase change material (PCM) was synthesized by converting biowaste rice into ultralight (0.08 g/cm3) hierarchical porous carbon (CNR) to pack polyethylene glycol (PEG) PCM. The thermal property and corresponding mechanism were analyzed. The results show that the composite PCM exhibits excellent thermal storage efficiency (93.3 %), considerable solar photothermal conversion efficiency and superior thermal stability. The interfacial thermal resistance (ITR) of PEG/CNR is 73 % lower than graphene foam-based composite PCM thus a fast transient temperature response. Particularly, the package of PEG endowed composite PCM with elastic characteristic thereby an enhanced compressive strength. Furthermore, covering PEG/CNR results in a delay of approximately 1.3 times in reaching the peak temperature on the surface of electronic components, and a delay of 5 times in cooling time. This study presents solid guidelines for societal development that is sustainable and makes some recommendations for construction of composite PCMs combining multifunctional applications.

Preparation of water-based dextran-coated Fe3O4 magnetic fluid for magnetic hyperthermia

Abstract Fe3O4 nanoparticles were prepared by chemical co-precipitation, modified with dextran, and dispersed in water to form a magnetic fluid (MF) for use in biomedical areas. The analyses of stability and magnetic property demonstrate that the prepared functional MF possesses outstanding stability (stability index within 60 days, high dilution stability, and autoclaved stability) and high magnetization (the values χ and M s of MF are 5.87 × 10−4 and 20.57 emu/g, respectively). Due to the coating of dextran, the toxicity of MF is minimal (in vitro survival rate of MCF-7 cells, blood compatibility, and in vivo toxicity). In addition, although the outer layer is coated with dextran, the M s intensity remains high, so the Fe3O4 MF owns a fast magnetic temperature response (when the MF concentration is 55 mg/mL, it can rapidly rise to 55°C within 800 s), which plays an extremely vital role in MF hyperthermia. So, the MF can effectively cause necrosis of human lung A549 cells, which shows a certain application potential.

Multi-layer carbon fiber paper @reduced graphene oxide/Co/C composite with adjustable electromagnetic interference shielding properties

Paper-based composite materials exhibit a marked tendency towards thinner and lighter profiles in the context of electromagnetic interference (EMI) shielding. Carbon fiber paper (CFP) has excellent electrical conductivity and Lightweight base characteristics. However, its single electrical loss characteristic and uncontrollable EMI shielding performance are limited in application. Therefore, we prepared CFP@ graphene oxide (GO)/ZIF-67 composites by chemical bonding and in-situ polymerization, and then prepared CFP@rGO/Co/C composites with integrated structure and function by heat treatment. Layer-by-layer assembly technology was employed to develop composite materials with tunable EMI shielding performance. The composite material has excellent high conductivity (2475.86 S/m) and excellent EMI shielding performance (average X-band EMI efficiency (SE)38.46 dB, absolute shielding effectiveness (SSE/t) = 14388.56 dB cm2 g−1). Through the layer-by-layer assembly technology, the EMI SE performance of the 7-layer assembled material reached 85.83 dB, and the EMI SSE/t reached 32110.51 dB cm2 g−1. Through simulation verification, the EMI shielding performance of the materials is compared, and ideas for EMI material design are provided. In addition, the material also has excellent Joule heating performance, fast electrothermal response and good temperature controllability. The material exhibits remarkable resilience against harsh environmental conditions, including strong acids, bases, organic reagents, ultrasonic waves, combustive processes, and extremely low temperatures. Despite these severe treatments, its performance remains above 90 % intact. This study proposes a magnetic-dielectric synergistic, performance-adjustable CFP-based shielding material, which has great application potential in the future wearable, defense, and aerospace fields.

Lignin with enhanced photothermal performance for the preparation of a sustainable solar-driven double-layer biomass evaporator

The undesirable photothermal conversion performance of lignin limits the potential for directing use as a photothermal conversion material, and no strategies have been found to enhance the photothermal conversion efficiency of lignin. Herein, three modified lignin of corn stover alkali lignin (DEHL), pine alkali lignin (DAL) and birch alkali lignin (DTAL) with excellent photothermal conversion efficiency and fast temperature response was prepared by a one-step iodocyclohexane (ICH) activation strategy. The maximum temperature of the DEHL, DAL and DTAL can reach to 138 °C, 157 °C, and 172 °C in 12 min under 0.15 W/cm2 compared to the native lignin. Moreover, the photothermal conversion efficiency of the DEHL, DAL and DTAL was calculated to be 36.52 %, 36.19 % and 43.19 % by ICH modification. The photothermal enhancement mechanism of the modified lignin was determined by various characterizations and simulation calculations, which can be summarized that the activation of lignin by ICH breaks the molecular structure and reduces the methoxy content of the lignin, which enhances the intermolecular bonding, and the hydrogen bonding between the phenolic hydroxyl groups strengthens the π-π intermolecular interactions between the benzene rings. In addition, a double-layer biomass aerogel evaporator (DAGS) with cost-friendly and superior evaporation performance was synthesized by chemical cross-linking using DTAL as the photothermal agent. The evaporation rate of 4DAGS can be as high as 2.063, 2.024, 2.259 and 2.447 kg/(m2∙h) in water, 3.5 wt% seawater, and 200 mg/L of MG or MB wastewater under 1sun. And no salt was observed on the surface of the 4DAGS after a long period of 36 h of operation in 3.5 wt% seawater, suggesting the outstanding salt-reject performance of the aerogel. Furthermore, there is no structural damage and chemical decomposition found on 4DAGS after 24 h immersion in NaOH and HCl solutions, demonstrating the excellent acid and alkali resistance of the synthesized aerogels. This work may offer a novel strategy for the photothermal performance enhancement of lignin and expand the potential application in solar-driven evaporation materials.

A novel fast response and high precision water temperature sensor based on Fiber Bragg Grating

A novel fast response and high precision water temperature sensor scheme based on gallium alloy sensitivity enhanced Fiber Bragg Grating(FBG) is proposed and experimentally demonstrated. In order to achieve faster temperature response speed of the sensor, a fiber Bragg grating is encapsulated in a single-end sealed metal tube which is filled with liquid gallium alloy. The very high thermal conductivity of the liquid gallium alloy that is filled in the metal tube gives rise to an experimental sensitivity of 30 pm/℃. Thanks to accurate and optimal design of metal tube structure parameters, the sensor exhibits an excellent response speed of 43 ms/℃ in water. Very good linearity between center wavelength of FBG and temperature is also achieved in the experiment. The research result of this paper is especially useful for applications where rapid temperature response and high precision are required at the same time, such as ocean CTD(Conductivity Temperature Depth) measuring equipment, ocean hydrology and underwater submersible.

High-sensitive temperature sensing use NIR upconversion luminescence of Er3+-core@Tm3+-shell with good robustness

In recent years, lanthanide doped materials have been extensively studied in the field of fluorescence temperature sensing due to their abundant emission levels and sensitive thermal response. Temperature sensing based on fluorescence intensity ratio (FIR) of upconversion nanoparticles has the advantages of fast temperature response, non-aggressiveness, and high spatial resolution. However, the most reported FIR sensing has limited sensitivity, probably due to the use of thermal coupling levels. Herein, we report a novel FIR temperature measurement based on non-thermal coupling levels of NaGdF4:Yb3+/Er3+@NaGdF4@NaGdF4:Yb3+/Tm3+ core-shell-shell nanostructure, which has high sensitivity and robustness simultaneously. The relative sensitivity based on I801/I654 and I801/I841 of Tm3+ to Er3+ can reach up to 4.56 (303 K) and 3.82% K−1 (313 K), respectively. Between them, FIR of I801/I841 is independent of excitation power and time. These results show the great potential of FIR based on non-thermal coupling levels in high-sensitive and robust temperature sensors.

Development of a compact high-power density air-cooled proton exchange membrane fuel cell stack with ultrathin steel bipolar plates

Air-cooled fuel cells used in portable stacks are required to reduce the size and weight while ensuring a high-power output. In this study, the 0.1 mm stainless steel sheet was used to form the ultrathin bipolar plates (BPs), by the reasonable flow field design and material selection, the mass of single bipolar plate is as low as 44.6 g and the thickness is only 1.9 mm with 180 cm−2 active area. The 2.8 kW air-cooled stack has efficient heat dissipation, small voltage over/undershoot, rapid temperature dynamic response, and compact structure, moreover, the mass of the stack core is 3203 g and the volume of the stack is 3.36 L. The designed stack has an excellent voltage consistency, fast temperature response, and high power density. The maximum voltage overshoot is 0.035 V with a current step/drop of 10 A. The maximum temperature drop rate reaches 0.12 K s−1 in a 10% fan duty cycle step when the load current is 72 A. At 50% fan duty cycle, the temperature increase rate reaches its peak of 0.27 K s−1 when the load current steps from 70 A to 80 A. The mass power density of the designed air-cooled 56-cell stack is 0.885 kW kg−1 and the volumetric power density is 0.751 kW L−1.

Gecko-inspired self-adhesive packaging for strain-free temperature sensing based on optical fibre Bragg gratings

The large development of fibre Bragg gratings (FBGs) over decades has made this kind of structures one of the most mature optical fibre sensing technologies existing today, demonstrating key features for a very wide range of applications. FBG sensors are fragile and must be normally protected for real-field applications, although challenging packaging designs are required to mitigate temperature-strain cross-sensitivity issues. Here, a polydimethylsiloxane (PDMS) packaging with a microarray structure that provides gecko-inspired dry adhesion is proposed for strain-free FBG-based temperature sensing. Besides offering protection, the PDMS packaging with an embedded polyamide capillary damps the mechanical strain transferred to the optical fibre, providing FBG-based temperature sensing with a negligible impact of strain. In addition, the microarray structure imprinted on one surface of the packaging provides gecko-inspired dry adhesion based on van der Waals forces. This feature enables the packaged optical fibre sensor to be attached and detached dynamically to nearly any kind of smooth surface, leaving no residuals in the monitored structure. Experimental results verify a fast and accurate temperature response of the sensor with highly mitigated impact of residual strain. The proposed packaged sensor can be used in application where glue is not allowed nor recommendable to be used.

High-performance electrothermal coatings based on natural flake graphite for multifunctional electrothermal applications

Electrothermal elements are used in electronic devices, physiotherapy, and health care due to their lightweight and fast temperature response. However, the high cost and susceptibility to oxidation of traditional electrothermal materials limit their application. In this work, a low-cost, environment-friendly, controllable, and high-performance natural flake graphite-based electrothermal coating is proposed that can be used in various electrothermal applications. The results demonstrate that the morphology and electrothermal properties of the coatings can be controlled based on pressure engineering and the use of various adhesives. The uncompressed electrothermal coatings can reach a maximum temperature of 157.9 °C and a maximum electric conductivity of 27.89 S/m at 36 V, whereas the compressed coatings can reach a maximum temperature of 199 °C at only 18 V and a maximum conductivity of 433.6 S/m, which is 22 times higher than the corresponding uncompressed coatings. This work provides a low-cost, high-performance, and well-attainable industrialization path for the application of natural graphite-based electrothermal coatings in indoor heating, light electrothermal clothing, and snow and ice removal.

Heat transfer process analysis and performance research of micro heat pipe array applied for the thermal management of proton exchange membrane fuel cells

• A new PEMFC thermal management method based on micro heat pipe array is proposed. • Micro heat pipe array has fast thermal response and good temperature uniformity. • Micro heat pipe array can enhance the heat dissipation capacity of PEMFC. Effective thermal management is critical for the safe and efficient operation of proton exchange membrane fuel cells (PEMFC). The small temperature difference between the stack and the environment brings greater challenges to the cooling system. This study proposes the integration of micro heat pipe arrays (MHPA) into bipolar plates for thermal management of small-power air-cooled PEMFC. The heat transfer performance of 2 mm MHPA under air-cooled conditions is experimentally studied, and a comparative study is conducted on the actual application of air-cooled PEMFC. The results show that the MHPA can reach a steady state within 600∼900 s when the heating power is changed. The minimum thermal resistance of the MHPA is 0.53 K/W, the uniform temperature distribution in the evaporation zone is very uniform within 2 K, showing a small heat transfer thermal resistance and good temperature uniformity performance. When the maximum temperature inside the stack does not exceed 65 ℃, the maximum output power of the MHPA-PEMFC is 25.66% higher than that of the traditional air-cooled PEMFC, and the maximum temperature difference inside the stack is reduced by 50.1%. The results of this study provide a theoretical basis for the application potential of MHPA in PEMFC thermal management.

Experimental and modeling investigation on thermal risk evaluation of tabs for pouch-type lithium-ion battery and the relevant heat rejection strategies

Thermal safety is one of the primary requirements for electric vehicles (EVs). Overheating by an external or internal heat source will induce the onset of thermal runaway. An overheating risk caused by tabs of pouch-type lithium-ion batteries was reported and the relevant heat rejection strategies were investigated in this paper. The positive tab showed a much higher temperature rise than that in the body and the negative tab of pouch-type lithium-ion batteries. The temperature reached 70.4 °C in the beginning 100 s with a charge rate of 2 C-rate, showing a fast temperature response. Besides, the largest temperature difference between the charge and discharge process was about 20.2 °C (2 C-rate), which indicates that the positive tab in the charging process is more dangerous than that in discharging process. Moreover, an electro-thermal model was applied to investigate the potential risk of tabs in the pouch-type lithium-ion battery. An extreme temperature rise (∼ 350 °C) in the positive tab showed a potential thermal risk in a high charging rate (6C). And the temperature at the tab can only be controlled under a relatively high heat transfer coefficient (higher than 100 W·m−2·K−1). This work is meaningful for the development of a thermal management strategy in a battery pack with fast charging technologies.

Microwave heating of carbon materials for on-demand thermal patterning via tunable electromagnetic resonators

Recently, thermal manipulation in carbon materials has drawn much interest in multiple domains. Compared with existing conductive heating techniques, microwave heating has many advantages such as non-contact heating, fast and accurate temperature response, low energy consumption, etc. However, it is still challenging to realize real-time on-demand thermal manipulation in carbon materials with microwaves, due to the lack of effective control methods on electromagnetic (EM) properties. Here, for the first time, we report a solution to this problem by employing tunable EM resonators. Specifically, EM resonators with electrically tunable lumped elements were designed to couple microwave energy into the carbon material, realizing a pixel-controlled microwave heating performance. Through carefully designing the structure of the EM resonators, the local energy concentration on the tunable lumped elements was remarkably alleviated. Experimental results indicated that the microwave absorbance can be tuned from 12.1% to 99.6%, leading to a tunable heating rate ranging from 1.3 °C/min to 13.5 °C/min under fixed microwave power of 600 W. Moreover, a pixelated thermal manipulation was demonstrated through a thermal display of Arabic numerals. Our work may open new avenues for thermal manipulation in carbon materials and can be applied to complex thermal tasks such as customized materials processing, thermal display, deicing and defrosting, etc.

Large-scalable fabrication of liquid metal-based double helix core-spun yarns for capacitive sensing, energy harvesting, and thermal management

Yarn-based flexible sensors are the crucial components of intelligent wearable electronics. However, the mass fabrication of high-performance yarn sensors with multifunctional and wear-comfortable remains a challenge. Herein, liquid metal-based double helix core-spun yarns (DHCYs) can be massively produced via a facile friction core-spinning for human motion monitoring, energy harvesting and thermal management. Due to the stable double helix and hierarchical structure, the yarn and its fabric exhibit combined superiority of flexibility, breathability and washability. The yarn strain sensor demonstrates a good workable range (100%), high sensitivity, ultra-low hysteresis and high durability (6000 cycles). For energy harvesting, the plain-woven fabric exhibits the excellent triboelectric performance of 50 V open-circuit voltage (VOC), 500 nA short-circuit current (ISC), and 100 nC short-circuit transferred charge (QSC). Moreover, owing to the high electrical conductivity of liquid metal, the DHCYs present a fast temperature response and achieve a stabilized temperature from 16 ℃ to 45 ℃ within 80 s under 6 V. As proof of concept, we demonstrate the electrothermochromism and heat preservation of DHCYs, indicating its great potential in smart textiles, wearable devices and human-machine interfaces.

Design and analysis of electrothermal metasurfaces

Electrothermal metasurfaces have attracted extensive attention due to their ability to dynamically control thermal infrared radiation. Although previous studies were mainly focused on the metasurfaces with infinite unit cells, the finite-size effect can be a critical design factor for developing thermal metasurfaces with fast response and broad temperature uniformity in practice. Here, we study the thermal metasurfaces consisting of gold nanorods with a finite array size, which, with only several periods, can achieve a resonance close to that of the infinite case. More importantly, such a small footprint due to the finite array size results in the response time down to a nanosecond level. Furthermore, the number of the unit cells in the direction perpendicular to the axis of the nanorods is found to be insensitive to the resonance and response time, thus providing a tunability in aspect ratio that can boost the temperature uniformity in the sub-Kelvin level.

Nonwoven carbonized viscose mat for outstanding electromagnetic shielding, fast electrical heating and fire alarm

Disposable face towel derived amorphous carbon prepared by annealing for broad and exacting applications in electromagnetic shielding, electrical heating, etc. This mat with 3D conductive network formed by nonwoven viscose fiber structure gives an outstanding electromagnetic shielding performance of 30 dB and 8161 dB/(g/cm2) at a thickness of 0.168 mm in the frequency range of 0.3–3.0 GHz. In addition, the as prepared mat presents excellent temperature & strain sensing with exceptional sensitivity (BS = 5.5%), and favorable flexibility (1000 bending cycles without fracture). Moreover, the mat provides well Joule heating performance, and the heating temperature can reach over 60°C in 32 seconds under 0.25 A current. More interestingly, the mat shows excellent fire alarm with a fast response (84 ms) and high operating temperature (>500°C). This method provides a simple and low-cost new method for radiation protection, temperature detection, fire alarm and other fields.

Strong temperature influence and indiscernible ventilation effect on dynamics of some semivolatile organic compounds in the indoor air of an office.

Many manmade organic air pollutants are semivolatile and primarily used and exposed indoors. It remains unclear how indoor environmental parameters affect indoor air dynamics of semivolatile organic compounds (SVOCs) in real-world indoor conditions, which directly relates to human exposure. By making time-resolved SVOC measurements over multiple weeks in an office, we characterized the indoor air dynamics of six representative SVOCs which were mainly present in the gas phase and of indoor origins, and investigated the effects of the temperature and ventilation rate. The six species include di-isobutyl phthalate and di-n-butyl phthalate, as well as two n-alkanes and two siloxanes. Airborne concentrations of all six SVOCs responded strongly and quickly to changes in the indoor temperature. The temperature dependence of individual species can be well fitted in the form of the van't Hoff equation, and explained 65-86% of the observed variation in the logarithm-transformed concentrations. In contrast, increasing the ventilation rate by a factor of 3-5 for hours at a constant temperature had no discernible influence on the SVOC concentrations. Further kinetic modeling analysis suggests that the observed fast temperature response and indiscernible ventilation effect are both associated with SVOC sorption onto indoor surfaces, which dramatically slows the response of SVOC concentration to changes in the ventilation rate and speeds up the response to changes in the temperature. These results highlight the importance of sorption reservoirs on regulating indoor SVOC dynamics and also have important implications for controlling and assessing indoor air exposure to SVOCs.

High-solid content, low viscosity and long-term stability Mn–Co–Ni–O ceramic slurry for the fabrication of free-standing ultrathin NTC sheets

This study systematically investigated the relationships between Mn–Co–Ni–O ceramic slurry formulations and their volatility, rheology and stability, as well as the electrical properties of free-standing ultrathin sheets made from them. A ceramic slurry with a high solid content of 90%, viscosity <12,000 mPa s, and 720 h long-term stability was successfully obtained by optimizing a spherical clusters powder and organic carrier. The powder was formed by secondary aggregation, which reinforced the wettability of its surfaces. Such spherical clusters ensure that the powders created for ceramic slurry are compact and have good fluidity features microscopically. The optimal formula of the organic carrier system contained three components: 90 wt% organic solvent, 5 wt% ethyl cellulose and 5 wt% Span85. Meanwhile, an organic solvent was made with terpineol, butyldiglycol, 2-(2-butoxyethoxy) ethyl acetate at a ratio of 70:10:20. Mn–Co–Ni–O free-standing ultrathin sheets were prepared by a screen printing method using this slurry, which had a resistivity of 278.25 Ω cm at 25 °C, thermal constant of 3404.3 K, activation energy of 0.29 eV, and temperature coefficient of resistance of −3.83%/K. Furthermore, the response time of a small thermal sensor based on this sheet reached 32 ms. Such Mn–Co–Ni–O free-standing ultrathin sheets with excellent negative temperature coefficient characteristics are promising candidates for fast response temperature measurement.

Ultrasensitive Thermochromic Upconversion in Core-Shell-Shell Nanoparticles for Nanothermometry and Anticounterfeiting.

Upconversion nanoparticle based ratiometric nanothermometry has shown many advantages including high relative sensitivity, fast temperature response, and high spatial resolution. However, most of the existing designs are on the basis of thermally coupled upconversion emissions, and it remains a challenge to improve the thermo-sensitivity. Here, we report a new nanoplatform of NaYF4:Yb/Er/Ce@NaYF4@NaYF4:Yb/Tm core-shell-shell nanostructure to improve the thermal sensitivity through the nonthermally coupled upconversion emissions. With the increase of temperature, the green upconversion of Er3+ shows a decline while the blue upconversion of Tm3+ exhibits a rapid increase, leading to a huge contrast in both intensity ratio and emission colors. The maximum relative sensitivity can reach up to 9.86% K-1 at 303 K. It is further found that introducing Ce3+ is able to improve the sensitivity and expand the thermochromic green-to-blue gamut greatly. These results show great potential in ultrasensitive lanthanide-based nanothermometry and anticounterfeiting.