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Mortar beams incorporating carbon nanofibers (CNFs), which were synthesized in situ on Portland cement particles, were used to produce nanomodified Portland cement sensors (SmartCem sensors). SmartCem sensors exhibited an electrical response comparable to a thermistor with a temperature coefficient of resistivity of − 0.0152/ °C. The highest temperature sensing was obtained for the SmartCem sensor, which contained ~ 0.271 wt.% of CNFs. The calculated temperature sensitivity was approximately 11.76% higher in comparison with the mortar beam containing only unmodified Portland cement. SmartCem sensors were used to monitor the cement hydration in large-scale self-compacting concrete beams. The measurements were conducted after casting for 7 days. Additionally, commercially available thermocouple and humidity sensors were used as references. The results showed that changes in electrical resistivity measured by the SmartCem sensor were well aligned with the ongoing hydration processes., Validerad;2023;Nivå 2;2023-12-04 (joosat);Full text license: CC BYThis article has previously appeared as a manuscript in a thesis.

Mortar beams incorporating carbon nanofibers (CNFs), which were synthesized in situ on Portland cement particles, were used to produce nanomodified Portland cement sensors (SmartCem sensors). SmartCem sensors exhibited an electrical response comparable to a thermistor with a temperature coefficient of resistivity of − 0.0152/ °C. The highest temperature sensing was obtained for the SmartCem sensor, which contained ~ 0.271 wt.% of CNFs. The calculated temperature sensitivity was approximately 11.76% higher in comparison with the mortar beam containing only unmodified Portland cement. SmartCem sensors were used to monitor the cement hydration in large-scale self-compacting concrete beams. The measurements were conducted after casting for 7 days. Additionally, commercially available thermocouple and humidity sensors were used as references. The results showed that changes in electrical resistivity measured by the SmartCem sensor were well aligned with the ongoing hydration processes., Validerad;2023;Nivå 2;2023-12-04 (joosat);Full text license: CC BYThis article has previously appeared as a manuscript in a thesis.

This work presents a continuous volumetric indoor air temperature measurement scheme using PMUTs (piezoelectric micromachined ultrasonic transducers). Advancements as compared to state-of-art works include: (1) 'volumetric' temperature monitoring instead traditional 'pointwise' temperature information; (2) accurate temperature readings spanning an operational distance of 5 m as validated by a commercial thermometer for 3 days; and (3) capable of detecting global average temperature and local temperature events by installing networked/grid PMUT pairs. This innovative sensing technique could be applicable for the precision control of future building/living environments.

Mortar sensors were fabricated as beams incorporating different amounts of carbon nanofibers (CNFs) synthesized in-situ on cement particles. Changes in electrical resistivity were measured and compared to recorded changes in compressive stress, temperature, and humidity. Sensing mechanisms and corresponding models were developed. The findings of the study indicate that the piezoresistive effect is influenced by the critical concentration of CNFs inside the composite matrix and the tunneling effect. In addition, water absorption and desorption, as well as the amount of chemically bound water played an important role in humidity sensing. Thermal fluctuation-induced tunneling conduction was dominant for the temperature sensitivity., Validerad;2024;Nivå 2;2024-06-03 (joosat);Funder: Skanska Sverige;Full text license: CC BY

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 stable 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., Validerad;2024;Nivå 2;2024-07-10 (joosat);Funder: Xunta de Galicia (Conselleria de Cultura, Educacion e Universidade) (ED481B-2021-082); Full text license: CC BY 4.0

Mortar sensors were fabricated as beams incorporating different amounts of carbon nanofibers (CNFs) synthesized in-situ on cement particles. Changes in electrical resistivity were measured and compared to recorded changes in compressive stress, temperature, and humidity. Sensing mechanisms and corresponding models were developed. The findings of the study indicate that the piezoresistive effect is influenced by the critical concentration of CNFs inside the composite matrix and the tunneling effect. In addition, water absorption and desorption, as well as the amount of chemically bound water played an important role in humidity sensing. Thermal fluctuation-induced tunneling conduction was dominant for the temperature sensitivity., Validerad;2024;Nivå 2;2024-06-03 (joosat);Funder: Skanska Sverige;Full text license: CC BY

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 stable 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., Validerad;2024;Nivå 2;2024-07-10 (joosat);Funder: Xunta de Galicia (Conselleria de Cultura, Educacion e Universidade) (ED481B-2021-082); Full text license: CC BY 4.0

Temperature sensing and monitoring play a vital role in various applications. Non-invasive, item-level temperature sensing methods that require no direct line of sight with the measuring object are attractive. This paper presents such a temperature sensing method using commodity RFID tags with no infrastructure changes. RFID tags are widely deployed for product identification purposes. We explore the possibility of leveraging the RSSI measurements from commodity RFID tags for temperature sensing. Essentially, we model a relationship between the temperature and the relative permittivity of a material in terms of RSSI. Our method can measure temperature in the range of 22°C to 60°C and achieves a measurement accuracy of 2°C with a mean error of 1.5°C.

Temperature sensing and monitoring play a vital role in various applications. Non-invasive, item-level temperature sensing methods that require no direct line of sight with the measuring object are attractive. This paper presents such a temperature sensing method using commodity RFID tags with no infrastructure changes. RFID tags are widely deployed for product identification purposes. We explore the possibility of leveraging the RSSI measurements from commodity RFID tags for temperature sensing. Essentially, we model a relationship between the temperature and the relative permittivity of a material in terms of RSSI. Our method can measure temperature in the range of 22°C to 60°C and achieves a measurement accuracy of 2°C with a mean error of 1.5°C.

Ongoing developments in science and technology require temperature measurements at increasingly higher spatial resolutions. Nanocrystals with temperature-sensitive luminescence are a popular thermometer for these applications offering high precision and remote read-out. Here, we demonstrate that ratiometric luminescence thermometry experiments may suffer from systematic errors in nanostructured environments. We place lanthanide-based luminescent nanothermometers at controlled distances of up to 600 nm from a Au surface. Although this geometry supports no absorption or scattering resonances, distortion of the emission spectra of the thermometers due to the modified density of optical states results in temperature read-out errors of up to 250 K. Our simple analytical model explains the effects of thermometer emission frequencies, experimental equipment, and sample properties on the magnitude of the errors. We discuss the relevance of our findings in several experimental scenarios. Such errors do not always occur, but they are expected in measurements near reflecting interfaces or scattering objects.

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.

Temperature sensing and monitoring play a vital role in various applications. Non-invasive, item-level temperature sensing methods that require no direct line of sight with the measuring object are attractive. This paper presents such a temperature sensing method using commodity RFID tags with no infrastructure changes. RFID tags are widely deployed for product identification purposes. We explore the possibility of leveraging the RSSI measurements from commodity RFID tags for temperature sensing. Essentially, we model a relationship between the temperature and the relative permittivity of a material in terms of RSSI. Our method can measure temperature in the range of 22°C to 60°C and achieves a measurement accuracy of 2°C with a mean error of 1.5°C.

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.

Temperature sensing and monitoring play a vital role in various applications. Non-invasive, item-level temperature sensing methods that require no direct line of sight with the measuring object are attractive. This paper presents such a temperature sensing method using commodity RFID tags with no infrastructure changes. RFID tags are widely deployed for product identification purposes. We explore the possibility of leveraging the RSSI measurements from commodity RFID tags for temperature sensing. Essentially, we model a relationship between the temperature and the relative permittivity of a material in terms of RSSI. Our method can measure temperature in the range of 22°C to 60°C and achieves a measurement accuracy of 2°C with a mean error of 1.5°C.

In this work, we demonstrate the usability of a fully-2D-material based device consisting of MoS2/WSe2 heterojunction encapsu-lated 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 characteris-tics. From this, we had a deeper look on the current transport mechanism by obtaining the activation energy of the saturation current in the Arrhenius diagram. It is 1.3 eV, which can be related to the bandgap of MoS2 or WSe2 (both nominal 1.3 eV) as for traditional pn-junction diodes in bulk materials. Further-more, we applied a constant forward current to the device while measuring the voltage drop at different temperatures to investi-gate the temperature-sensor performance. In the range of 40 K up to 300 K, the sensitivity of the sensor is ~2 mV/K, which is comparable to Si devices, while the linearity is still lower (R2 ~ 0.94). On the other hand, the demonstrated device consists only of 2D materials and is, thus, substrate independent, ultra-thin, and can be fabricated on a fully flexible substrate in a low-cost process.

Nanomechanical resonators have become integral to technological advancements and scientific progress in modern society. Not only do they enable exquisite precision in sensing applications, but they also allow for exploring quantum mechanics and the development of quantum technologies. These applications require resonators with high quality factors capable of isolating them from environmental noise, specifically crucial at room temperature. The focus of this thesis is on investigating the limits of quality factors in nanomechanical resonators operating at room temperature. The study revolves around four main facets, addressing limitations in fabrication techniques, and design strategies, exploring the impact of aspect ratio on quality factor enhancement, and investigating the potential for temperature sensing. Firstly, we address the limits imposed by current fabrication techniques to realize high aspect ratio resonators, such as stiction and collapse due to interfacial forces like capillary. To overcome these challenges, we develop and characterize an SF6 plasma etching technique which enables a quick and controllable release of nanomechanical resonators. The high fidelity achieved through this approach allows the use of advanced optimization strategies to design resonators with exceptional quality factors. In doing so, we tackle the limits of design strategies, which have primarily relied on human intuition until now. By harnessing the power of Bayesian Optimization and inspired by nature, we discover a strategy to increase the quality factor at low order mode via a torsional soft-clamping mechanism. The experimental validation of the resulting spiderweb resonators confirms quality factors surpassing 1 billion at room temperature in the kHz frequency range. Notably, these resonators contain no features smaller than 1 micrometer, ensuring a fast and cost-effective fabrication. Expanding on these findings, the thesis explores the, Dynamics of Micro and Nano Systems

Temperature sensing and monitoring play a vital role in various applications. Non-invasive, item-level temperature sensing methods that require no direct line of sight with the measuring object are attractive. This paper presents such a temperature sensing method using commodity RFID tags with no infrastructure changes. RFID tags are widely deployed for product identification purposes. We explore the possibility of leveraging the RSSI measurements from commodity RFID tags for temperature sensing. Essentially, we model a relationship between the temperature and the relative permittivity of a material in terms of RSSI. Our method can measure temperature in the range of 22°C to 60°C and achieves a measurement accuracy of 2°C with a mean error of 1.5°C.

This thesis explores the application of Distributed Temperature Sensing (DTS) technology to observe temperature gradients and turbulent eddies within and above a forest vegetation layer. Atmospheric temperature gradients tie directly to heat transfer, a primary mode of which are turbulent eddies. The goal in studying these elements is to enhance the understanding of land-atmosphere coupling, which plays a role in climate and weather modelling. The data collection took place in the first two weeks of November 2022 at a meteorology study site in Loobos, the Veluwe. A fiber optic cable was installed, running from the forest floor to 1.5 times the canopy height along a tower. The DTS technology provided high-resolution temperature measurements at one-second intervals. Fluctuations in these profiles could potentially be associated with turbulent eddies. By analyzing temperature profiles over time and integrating meteorological data, the study provided insights into the temporal evolution of vertical temperature distribution at the test site and its sensitivity to weather conditions. Phenomena such as direct sunlight, rainfall, canopy effects, and inversion layers were identified in the DTS data and validated with other meteorological measurements. Notably, sharp temperature inversions observed on two nights exhibited strong correlations with wind speed and its variation. Increases in wind speed and variability were associated with lower inversion heights., Civil Engineering

Die additive Fertigung hat in den letzten Jahren großes Interesse geweckt, da sie einige Vorteile gegenüber herkömmlichen Fertigungsverfahren aufweist. Trotz des Potenzials sind viele Anwendungen aufgrund von Zuverlässigkeitsproblemen und einer begrenzten Materialauswahl immer noch auf das Rapid Prototyping beschränkt. Diese wissenschaftliche Studie zeigt zwei Anwendungen, die über das Rapid Prototyping hinausgehen und dabei strukturelle und funktionelle Materialien verwenden. Zuerst wird ein probabilistischer Prozess für den Leichtbau mit Gitterstrukturen vorgeschlagen. Zweitens wird eine Materialformulierung entwickelt, die das Anisotropie-Problem der Schmelzschichtung löst und Funktionsintegration durch elektrische Leitfähigkeit sowie Temperatur- und Dehnungsmessung ermöglicht., Additive manufacturing has attracted great interest in recent years as it shows several advantages over conventional manufacturing techniques. Despite its potential, many applications are still limited to rapid prototyping due to reliability issues and a limited material choice. This study shows two applications that go beyond rapid prototyping using structural and functional materials. First, a probabilistic process for lightweight design with lattice structures is proposed. Second, a new material formulation is developed that solves the anisotropy issue of fused filament fabrication and allows functional integration by electrical conductivity as well as temperature and strain sensing.

The article proposes the implementation of a prototype module for the control of access to higher education institutions, in this case the Politecnico Colombiano Jaime Isaza Cadavid Poblado sectional through the temperature sensing biosafety protocol, the tool allows temperature capture and taking of personal data for each user who enters the institution automatically given the current situation due to Covid-19. For the implementation, the software and hardware of existing technologies that are used to capture the temperature in an automated way are characterized, from this, the most appropriate technology for the implementation is selected, using open-source libraries, to modify the source code according to the punctual need. Similarly, a web application is developed to enter personal data and replace the physical forms with a digital database., El presente artículo plantea la implementación de un módulo prototipo para el control de acceso a instituciones de educación superior, en este caso el Politécnico Colombiano Jaime Isaza Cadavid. Sede Poblado, a través del protocolo de bioseguridad sensado de temperatura. Esta herramienta permite la captura automática de temperatura y toma de datos personales para cada usuario que ingresa a la institución dada la situación que se presenta actualmente por el covid-19. Parala implementación se caracteriza el software y hardware de tecnologías ya existentes que se utilizan para capturar la temperatura de manera automatizada, a partir de esto se selecciona la tecnología más adecuada para la implementación utilizando librerías open source para modificar el código fuente según la necesidad puntual. De igual forma, se desarrolla una aplicación web para el ingreso de datos personales que reemplacen las planillas físicas por una base de datos digital

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---v in most of the measuring band down to 1 mHz, and reaching 20 µK/Hz---v 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., Peer Reviewed, Postprint (published version)

Nickel manganite nanocrystalline fibers were obtained by electrospinning and subsequent calcination at 400 °C. As-spun fibers were characterized by TG/DTA, Scanning Electron Microscopy and FT-IR spectroscopy analysis. X-ray diffraction and FT-IR spectroscopy analysis confirmed the formation of nickel manganite with a cubic spinel structure, while N2 physisorption at 77 K enabled determination of the BET specific surface area as 25.3 m2/g and (BJH) mesopore volume as 21.5 m2/g. The material constant (B) of the nanocrystalline nickel manganite fibers applied by drop-casting on test interdigitated electrodes on alumina substrate, dried at room temperature, was determined as 4379 K in the 20–50 °C temperature range and a temperature sensitivity of −4.95%/K at room temperature (25 °C). The change of impedance with relative humidity was monitored at 25 and 50 °C for a relative humidity (RH) change of 40 to 90% in the 42 Hzπ1 MHz frequency range. At 100 Hz and 25 °C, the sensitivity of 327.36 ± 80.12 kΩ/%RH was determined, showing that nickel manganite obtained by electrospinning has potential as a multifunctional material for combined humidity 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-LEDs operate in current constant mode, exhibiting an excellent performance with a sensitivity of 2.6/2.7/2.2 mV/K for blue/green InGaN micro-LEDs and red AlGaInP micro-LED under an injection current density of 1 mA/cm2, which is about two times lower sensitivity than the sensitivity limit obtained from the Shockley ideal diode equation. It is speculated that the lower sensitivity originated from parasitic resistances. It is also found that the band gaps of ternary InGaN and quaternary AlGaInP obtained from temperature-dependent electroluminescence spectra of red micro-LED agrees with the calculated values by using the semiempirical Varshni relationship. The EL of micro-LEDs is characterized by narrow emission widths of 18-41 nm, leading to wide color gamut covering up to 170/97% of the DCI P3/BT 2020, which are the standard color space of ultrahigh definition television system. © 2021 American Chemical Society.

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-LEDs operate in current constant mode, exhibiting an excellent performance with a sensitivity of 2.6/2.7/2.2 mV/K for blue/green InGaN micro-LEDs and red AlGaInP micro-LED under an injection current density of 1 mA/cm2, which is about two times lower sensitivity than the sensitivity limit obtained from the Shockley ideal diode equation. It is speculated that the lower sensitivity originated from parasitic resistances. It is also found that the band gaps of ternary InGaN and quaternary AlGaInP obtained from temperature-dependent electroluminescence spectra of red micro-LED agrees with the calculated values by using the semiempirical Varshni relationship. The EL of micro-LEDs is characterized by narrow emission widths of 18-41 nm, leading to wide color gamut covering up to 170/97% of the DCI P3/BT 2020, which are the standard color space of ultrahigh definition television system. © 2021 American Chemical Society.

The next-generation sutures should provide in situ monitoring of wound condition such as temperature while reducing surgical site infection during wound closure. In this study, functionalized nanodiamond (FND) and reduced graphene oxide (rGO) into biodegradable polycaprolactone (PCL) are incorporated to develop a new multifunctional suture with such capabilities. Incorporation of FND and rGO into PCL enhances its tensile strength by about 43% and toughness by 35%. The sutures show temperature sensing capability in the range of 25–40 °C based on the shift in zero-splitting frequency of the nitrogen-vacancy (NV–) centers in FND via optically detected magnetic resonance, paving the way for potential detection of infection or excessive inflammation in healing wounds. The suture surface readily coats with antibiotics to reduce bacterial infection risk to the wounds. The new suture thus is promising in monitoring and supporting wound closure.

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.

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-LEDs operate in current constant mode, exhibiting an excellent performance with a sensitivity of 2.6/2.7/2.2 mV/K for blue/green InGaN micro-LEDs and red AlGaInP micro-LED under an injection current density of 1 mA/cm2, which is about two times lower sensitivity than the sensitivity limit obtained from the Shockley ideal diode equation. It is speculated that the lower sensitivity originated from parasitic resistances. It is also found that the band gaps of ternary InGaN and quaternary AlGaInP obtained from temperature-dependent electroluminescence spectra of red micro-LED agrees with the calculated values by using the semiempirical Varshni relationship. The EL of micro-LEDs is characterized by narrow emission widths of 18-41 nm, leading to wide color gamut covering up to 170/97% of the DCI P3/BT 2020, which are the standard color space of ultrahigh definition television system. © 2021 American Chemical Society.

Nanocrystalline nickel manganite (NiMn2O4) powder with a pure cubic spinel phase structure was synthesized via sol-gel combustion and characterized with XRD, FT-IR, XPS and SEM. The powder was mixed with sodium alginate gel to form a nano-biocomposite gel, dried at room temperature to form a thick film and characterized with FT-IR and SEM. DC resistance and AC impedance of sensor test structures obtained by drop casting the nano-biocomposite gel onto test interdigitated PdAg electrodes on an alumina substrate were measured in the temperature range of 20-50 degrees C at a constant relative humidity (RH) of 50% and at room temperature (25 degrees C) in the RH range of 40-90%. The material constant obtained from the measured decrease in resistance with temperature was determined to be 4523 K, while the temperature sensitivity at room temperature (25 degrees C) was -5.09%/K. Analysis of the complex impedance plots showed a dominant influence of grains. The decrease in complex impedance with increase in temperature confirmed the negative temperature coefficient effect. The grain resistance and grain relaxation frequency were determined using an equivalent circuit. The activation energy for conduction was determined as 0.45 eV from the temperature dependence of the grain resistance according to the small polaron hopping model, while the activation energy for relaxation was 0.43 eV determined from the Arrhenius dependence of the grain relaxation frequency on temperature.

Nickel manganite nanocrystalline fibers were obtained by electrospinning and subsequent calcination at 400 degrees C. As-spun fibers were characterized by TG/DTA, Scanning Electron Microscopy and FT-IR spectroscopy analysis. X-ray diffraction and FT-IR spectroscopy analysis confirmed the formation of nickel manganite with a cubic spinel structure, while N-2 physisorption at 77 K enabled determination of the BET specific surface area as 25.3 m(2)/g and (BJH) mesopore volume as 21.5 m(2)/g. The material constant (B) of the nanocrystalline nickel manganite fibers applied by drop-casting on test interdigitated electrodes on alumina substrate, dried at room temperature, was determined as 4379 K in the 20-50 degrees C temperature range and a temperature sensitivity of -4.95%/K at room temperature (25 degrees C). The change of impedance with relative humidity was monitored at 25 and 50 degrees C for a relative humidity (RH) change of 40 to 90% in the 42 Hz pi 1 MHz frequency range. At 100 Hz and 25 degrees C, the sensitivity of 327.36 +/- 80.12 k omega/%RH was determined, showing that nickel manganite obtained by electrospinning has potential as a multifunctional material for combined humidity and temperature sensing.

A 6.4 nW 1.7% relative inaccuracy (R-IA) CMOS sub-thermal drain voltage-based temperature sensor is proposed. The proposed stabilized sub-thermal drain voltage current generator achieves a highly linear PTAT output without nonlinearity fitting or post-fabrication trimming and increases the accuracy of the sensor. A combination of the current generator and a frequency-locked loop relaxes the tradeoff between power and temperature stability of the current-to-frequency converter and achieves supply voltage-independent operation. Measured results of the prototype fabricated in a 65-nm CMOS process show that the proposed temperature sensor has a -1.0/+0.7 °C inaccuracy (= R-IA of 1.7%) while achieving a resolution of 75 mK over a temperature range of -30 °C to 70 °C. The line sensitivity of the sensor is 2.8 °C/V., Electronic Instrumentation

A 6.4 nW 1.7% relative inaccuracy (R-IA) CMOS sub-thermal drain voltage-based temperature sensor is proposed. The proposed stabilized sub-thermal drain voltage current generator achieves a highly linear PTAT output without nonlinearity fitting or post-fabrication trimming and increases the accuracy of the sensor. A combination of the current generator and a frequency-locked loop relaxes the tradeoff between power and temperature stability of the current-to-frequency converter and achieves supply voltage-independent operation. Measured results of the prototype fabricated in a 65-nm CMOS process show that the proposed temperature sensor has a -1.0/+0.7 °C inaccuracy (= R-IA of 1.7%) while achieving a resolution of 75 mK over a temperature range of -30 °C to 70 °C. The line sensitivity of the sensor is 2.8 °C/V., Electronic Instrumentation

When transporting perishable foods in the Cold Supply Chain (CSC), it is essential that they are maintained in a controlled temperature environment (typically from -1° to 10°C) to minimize spoilage. Fresh-food products, such as, meats, fruits, and vegetables, experience discoloration and loss of nutrients when exposed to high-temperatures. Also, medicines, such as, insulin and vaccines, can lose potency if they are not maintained at the appropriate temperatures. Consequently, the CSC is critical to the growth of global trade and to the worldwide availability of food and health supplies; especially, when considering that the retail food market consists mostly (approximately 65%) of fresh-food products. The current method of temperature monitoring in the CSC is limited to discrete location-based measurements. Subsequently, this data is used to assess the overall quality of transported goods. As a result, this method cannot capture all the common irregularities that can occur during the delivery cycle. Therefore, an effective sensor solution to monitor such items is necessary. Radio Frequency Identification (RFID) is a pragmatic wireless technology with a standardized communication protocol. Thus far, passive RFID temperature sensors have been investigated. However, each design has a limitation from which a set of design guidelines for an improved sensor solution is developed. That is, the new sensor should: (a) be compact to be applicable on individual products, (b) utilize purely passive technology to ensure longevity and cost-effectiveness, (c) monitor goods in a continuous fashion (e.g., operate through multiple room-to-cold and cold-to-room temperature cycles), and (d) operate in an independent mode, so that no resetting is required. In this research, antenna systems and RF circuit design techniques are combined with Liquid Crystal Elastomers (LCEs) to develop three novel temperature sensors. LCEs are temperature responsive polymers that are programmable and rever

This thesis describes the design of an ultra-low power temperature to digital converter. It is intended to monitor the excess heat produced during the wireless charging of implantable medical devices such as pacemakers. The TDC is designed to achieve an accuracy of ±0.1 °C (3 sigma) from 27 °C to 47 °C, and ±0.3 °C (3 sigma) from -40 °C to 85 °C after a 1-point trim. It also achieves a resolution of 0.01 °C at 10 Sa/s. The low power consumption (155 nW) is made possible by the implementation of a self-biasing BJT-core. Its low power consumption, accuracy, and resolution make it ideally suited for clinical temperature monitoring., Electrical Engineering | Microelectronics

The temperature evaluation through the measurement of emission intensities (intensity ratio method) require two distinct bands; one of which is used as a reference, and the emission intensity of other is monitored as a function of a change in temperature. Herein, we report the influence of excitation wavelengths, and a coupling scheme between lanthanoid and defect emission from the host lattice, to extend the temperature sensing range by using a single crystal of europium (III) phosphate. The temperature dependence of emission intensity was studied for different excitation wavelengths: 365 (intraconfigurational 4f2 excitation), 338 (defect excitation), and 254 nm (O2- →Eu3+ charge-transfer excitation), in the temperature range, 293--865 K. We determined the Boltzmann equilibrium among different coupling schemes using a linear regression model to infer that for an excitation at 338 nm wavelength, and evaluating the intensity ratio between defect emission and the Eu3+ 5D0,1 → 7FJ transitions, the temperature sensing range can be extended upto at least 865 K, with relative sensitivity in the range, 0.33-1.94%K-1 (at 750 K). The results showed resolution of < 1 K with an excellent reproducibility, suggesting that the thermometers can be used with high reliability.

This thesis describes the design of an ultra-low power temperature to digital converter. It is intended to monitor the excess heat produced during the wireless charging of implantable medical devices such as pacemakers. The TDC is designed to achieve an accuracy of ±0.1 °C (3 sigma) from 27 °C to 47 °C, and ±0.3 °C (3 sigma) from -40 °C to 85 °C after a 1-point trim. It also achieves a resolution of 0.01 °C at 10 Sa/s. The low power consumption (155 nW) is made possible by the implementation of a self-biasing BJT-core. Its low power consumption, accuracy, and resolution make it ideally suited for clinical temperature monitoring., Electrical Engineering | Microelectronics

Readily available temperature sensing in boilers is necessary to improve efficiencies, minimize downtime, and reduce toxic emissions for a power plant. The current techniques are typically deployed as a single-point measurement and are primarily used for detection and prevention of catastrophic events due to the harsh environment. In this work, a multi-point temperature sensor based on wavelength-multiplexed sapphire fiber Bragg gratings (SFBGs) were fabricated via the point-by-point method with a femtosecond laser. The sensor was packaged and calibrated in the lab, including thermally equilibrating at 1200 °C, followed by a 110-h, 1000 °C stability test. After laboratory testing, the sensor system was deployed in both a commercial coal-fired and a gas-fired boiler for 42 days and 48 days, respectively. The performance of the sensor was consistent during the entire test duration, over the course of which it measured temperatures up to 950 °C (with some excursions over 1000 °C), showing the survivability of the sensor in a field environment. The sensor has a demonstrated measurement range from room temperature to 1200 °C, but the maximum temperature limit is expected to be up to 1900 °C, based on previous work with other sapphire based temperature sensors.

[EN] We report the development of a temperature sensing probe created as a result of the combination of an optical fiber and a porous silicon microcavity (PSMC). After determining the physical parameters of the PSMC to achieve the required porous sensing structure, it was fabricated by electrochemically etching a silicon wafer. A 1-mm(2) PSMC piece was attached to the tip of an optical fiber so that temperature variations can be monitored in real-time exactly on that point. First, the performance of the PSMC sensor probe was characterized in a stable environment as water, obtaining a sensitivity around 110 pm/degrees C and a resolution in the 10-4 degrees C range. Afterward, the temperature transmission dynamics in air environment were studied.

Many organisms need to respond to complex, noisy environmental signals for developmental decision making. Here, we dissect how Arabidopsis plants integrate widely fluctuating field temperatures over month-long timescales to progressively upregulate VERNALIZATION INSENSITIVE3 (VIN3) and silence FLOWERING LOCUS C (FLC), aligning flowering with spring. We develop a mathematical model for vernalization that operates on multiple timescales-long term (month), short term (day), and current (hour)-and is constrained by experimental data. Our analysis demonstrates that temperature sensing is not localized to specific nodes within the FLC network. Instead, temperature sensing is broadly distributed, with each thermosensory process responding to specific features of the plants' history of exposure to warm and cold. The model accurately predicts FLC silencing in new field data, allowing us to forecast FLC expression in changing climates. We suggest that distributed thermosensing may be a general property of thermoresponsive regulatory networks in complex natural environments.

Many organisms need to respond to complex, noisy environmental signals for developmental decision making. Here, we dissect how Arabidopsis plants integrate widely fluctuating field temperatures over month-long timescales to progressively upregulate VERNALIZATION INSENSITIVE3 (VIN3) and silence FLOWERING LOCUS C (FLC), aligning flowering with spring. We develop a mathematical model for vernalization that operates on multiple timescales-long term (month), short term (day), and current (hour)-and is constrained by experimental data. Our analysis demonstrates that temperature sensing is not localized to specific nodes within the FLC network. Instead, temperature sensing is broadly distributed, with each thermosensory process responding to specific features of the plants' history of exposure to warm and cold. The model accurately predicts FLC silencing in new field data, allowing us to forecast FLC expression in changing climates. We suggest that distributed thermosensing may be a general property of thermoresponsive regulatory networks in complex natural environments.

[EN] We report the development of a temperature sensing probe created as a result of the combination of an optical fiber and a porous silicon microcavity (PSMC). After determining the physical parameters of the PSMC to achieve the required porous sensing structure, it was fabricated by electrochemically etching a silicon wafer. A 1-mm(2) PSMC piece was attached to the tip of an optical fiber so that temperature variations can be monitored in real-time exactly on that point. First, the performance of the PSMC sensor probe was characterized in a stable environment as water, obtaining a sensitivity around 110 pm/degrees C and a resolution in the 10-4 degrees C range. Afterward, the temperature transmission dynamics in air environment were studied.

[EN] We report the development of a temperature sensing probe created as a result of the combination of an optical fiber and a porous silicon microcavity (PSMC). After determining the physical parameters of the PSMC to achieve the required porous sensing structure, it was fabricated by electrochemically etching a silicon wafer. A 1-mm(2) PSMC piece was attached to the tip of an optical fiber so that temperature variations can be monitored in real-time exactly on that point. First, the performance of the PSMC sensor probe was characterized in a stable environment as water, obtaining a sensitivity around 110 pm/degrees C and a resolution in the 10-4 degrees C range. Afterward, the temperature transmission dynamics in air environment were studied.

Flexible electronics have become the subject of industry focus, generating a market desire for fully flexible temperature sensors. To the best of our knowledge, there are no current systems that can adequately satisfy both the mechanical flexibility and sensing performance demanded for commercial applications. This work focused on a design for a flexible temperature sensor by designing a thermistor using functional granular composites using ceramic NTC fibre particles and a resistive polymer matrix. The objective was to achieve good thermistor performance (high sensitivity: B-value > 3000 K, and low resistivity: rho ˜ 10^1 - 10^2 Ocm) while being mechanically flexible (surviving bending radii = 1 cm over 100 cycles). To achieve this objective this thesis work was organised into 5 major phases. Due to the high commercial value of NTC ceramic thermistors, no reference composition with its exact processing conditions are available in literature that produce a thermistor with commercially desirable properties. Phase 1 was therefore to select a NTC ceramic composition and Phase 2 was to investigate the necessary processing conditions to be able to produce bulk ceramics with adequate temperature sensing performance. Phase 3 involved making NTC ceramic fibres by wet fibre spinning and modifying the processing conditions developed in Phase 2. Phase 4 involved the selection of an appropriate polymer matrix and to attempt to create thermistor composites. Phase 5 involved creating more optimal composite thermistors using stencil printing and to test its thermistor and bending performance. Using an isotropic mixture of Mn2.4 Ni0.5 Cu0.1 O4 NTC ceramic fibre particles in an Electrodag matrix, composite thermistors were created by stencil printing onto thin-film substrates of polyethylene terephthalate that have silver inkjet printed interdigitate electrodes. A percolated network is formed with as little as 10 wt% of fibres (˜ 2.86 vol%). The composite with 10 wt% of fibres ha, Aerospace Engineering

Flexible electronics have become the subject of industry focus, generating a market desire for fully flexible temperature sensors. To the best of our knowledge, there are no current systems that can adequately satisfy both the mechanical flexibility and sensing performance demanded for commercial applications. This work focused on a design for a flexible temperature sensor by designing a thermistor using functional granular composites using ceramic NTC fibre particles and a resistive polymer matrix. The objective was to achieve good thermistor performance (high sensitivity: B-value > 3000 K, and low resistivity: rho ˜ 10^1 - 10^2 Ocm) while being mechanically flexible (surviving bending radii = 1 cm over 100 cycles). To achieve this objective this thesis work was organised into 5 major phases. Due to the high commercial value of NTC ceramic thermistors, no reference composition with its exact processing conditions are available in literature that produce a thermistor with commercially desirable properties. Phase 1 was therefore to select a NTC ceramic composition and Phase 2 was to investigate the necessary processing conditions to be able to produce bulk ceramics with adequate temperature sensing performance. Phase 3 involved making NTC ceramic fibres by wet fibre spinning and modifying the processing conditions developed in Phase 2. Phase 4 involved the selection of an appropriate polymer matrix and to attempt to create thermistor composites. Phase 5 involved creating more optimal composite thermistors using stencil printing and to test its thermistor and bending performance. Using an isotropic mixture of Mn2.4 Ni0.5 Cu0.1 O4 NTC ceramic fibre particles in an Electrodag matrix, composite thermistors were created by stencil printing onto thin-film substrates of polyethylene terephthalate that have silver inkjet printed interdigitate electrodes. A percolated network is formed with as little as 10 wt% of fibres (˜ 2.86 vol%). The composite with 10 wt% of fibres ha, Aerospace Engineering

Many organisms need to respond to complex, noisy environmental signals for developmental decision making. Here, we dissect how Arabidopsis plants integrate widely fluctuating field temperatures over month-long timescales to progressively upregulate VERNALIZATION INSENSITIVE3 (VIN3) and silence FLOWERING LOCUS C (FLC), aligning flowering with spring. We develop a mathematical model for vernalization that operates on multiple timescales-long term (month), short term (day), and current (hour)-and is constrained by experimental data. Our analysis demonstrates that temperature sensing is not localized to specific nodes within the FLC network. Instead, temperature sensing is broadly distributed, with each thermosensory process responding to specific features of the plants' history of exposure to warm and cold. The model accurately predicts FLC silencing in new field data, allowing us to forecast FLC expression in changing climates. We suggest that distributed thermosensing may be a general property of thermoresponsive regulatory networks in complex natural environments.

Many organisms need to respond to complex, noisy environmental signals for developmental decision making. Here, we dissect how Arabidopsis plants integrate widely fluctuating field temperatures over month-long timescales to progressively upregulate VERNALIZATION INSENSITIVE3 (VIN3) and silence FLOWERING LOCUS C (FLC), aligning flowering with spring. We develop a mathematical model for vernalization that operates on multiple timescales-long term (month), short term (day), and current (hour)-and is constrained by experimental data. Our analysis demonstrates that temperature sensing is not localized to specific nodes within the FLC network. Instead, temperature sensing is broadly distributed, with each thermosensory process responding to specific features of the plants' history of exposure to warm and cold. The model accurately predicts FLC silencing in new field data, allowing us to forecast FLC expression in changing climates. We suggest that distributed thermosensing may be a general property of thermoresponsive regulatory networks in complex natural environments.

Many organisms need to respond to complex, noisy environmental signals for developmental decision making. Here, we dissect how Arabidopsis plants integrate widely fluctuating field temperatures over month-long timescales to progressively upregulate VERNALIZATION INSENSITIVE3 (VIN3) and silence FLOWERING LOCUS C (FLC), aligning flowering with spring. We develop a mathematical model for vernalization that operates on multiple timescales-long term (month), short term (day), and current (hour)-and is constrained by experimental data. Our analysis demonstrates that temperature sensing is not localized to specific nodes within the FLC network. Instead, temperature sensing is broadly distributed, with each thermosensory process responding to specific features of the plants' history of exposure to warm and cold. The model accurately predicts FLC silencing in new field data, allowing us to forecast FLC expression in changing climates. We suggest that distributed thermosensing may be a general property of thermoresponsive regulatory networks in complex natural environments.

We propose an efficient model-based signal processing approach for optical fiber sensing with fiber Bragg grating (FBG) arrays. A position estimation based on an estimation of distribution algorithm (EDA) and a reflectivity estimation method using a parametric transfer matrix model (TMM) are outlined in detail. The estimation algorithms are evaluated with Monte Carlo simulations and measurement data from an incoherent optical frequency domain reflectometer (iOFDR). The model-based approach outperforms conventional Fourier transform processing, especially near the spatial resolution limit, saving electrical bandwidth and measurement time. The models provide great flexibility and can be easily expanded in complexity to meet different topologies and to include prior knowledge of the sensors. Systematic errors due to crosstalk between gratings caused by multiple reflections and spectral shadowing could be further considered with the TMM to improve the performance of large-scale FBG array sensor systems.

High-pressure microfluidics offers fast analyses of thermodynamic parameters for compressed process solvents. However, microfluidic platforms handling highly compressible supercritical CO2 are difficult to control, and on-chip sensing would offer added control of the devices. Therefore, there is a need to integrate sensors into highly pressure tolerant glass chips. In this paper, thin film Pt sensors were embedded in shallow etched trenches in a glass wafer that was bonded with another glass wafer having microfluidic channels. The devices having sensors integrated into the flow channels sustained pressures up to 220 bar, typical for the operation of supercritical CO2. No leakage from the devices could be found. Integrated temperature sensors were capable of measuring local decompression cooling effects and integrated calorimetric sensors measured flow velocities over the range 0.5-13.8 mm/s. By this, a better control of high-pressure microfluidic platforms has been achieved., Part financed through Swedish Agency for the Innovation System, Vinnova, through the Centre for Natural Disaster Science (CNDS)

High-pressure microfluidics offers fast analyses of thermodynamic parameters for compressed process solvents. However, microfluidic platforms handling highly compressible supercritical CO2 are difficult to control, and on-chip sensing would offer added control of the devices. Therefore, there is a need to integrate sensors into highly pressure tolerant glass chips. In this paper, thin film Pt sensors were embedded in shallow etched trenches in a glass wafer that was bonded with another glass wafer having microfluidic channels. The devices having sensors integrated into the flow channels sustained pressures up to 220 bar, typical for the operation of supercritical CO2. No leakage from the devices could be found. Integrated temperature sensors were capable of measuring local decompression cooling effects and integrated calorimetric sensors measured flow velocities over the range 0.5-13.8 mm/s. By this, a better control of high-pressure microfluidic platforms has been achieved., Part financed through Swedish Agency for the Innovation System, Vinnova, through the Centre for Natural Disaster Science (CNDS)