Body Heat Research Articles

Robust bendable thermoelectric generators enabled by elasticity strengthening.

Using body heat for instance, thermoelectric generators have promising applications for driving wearable electronics continuously but remain a challenge in terms of recoverable flexibility, as known highly-performing thermoelectrics are usually inorganics showing rigidity. It is conceptualized in this work a large elastic strain ensuring both a largely-curved recoverable bending and a full recoverability in thermoelectric performance after enormous bendings. This leads the current work to focus on a microstructure engineering approach for strengthening the elasticity of Ag2Se, in which dense dislocations and refined grain induced by a multi-pass hot-rolling technique enable a significant enhancement in elasticity. The resultant hot-rolled elastic thin thermoelectric generators realize a record bendability, for at least 1,000,000 times at a tiny bending radius of 3 mm with an extraordinary power density. Such a bendability is applicable to the most curved surfaces of a human body, suggesting a promising strategy for powerful wearable thermoelectrics of all inorganics.

Assessment of early neonatal practices to prevent hypothermia ; A comparative study.

Globally, neonatal deaths are significantly attributed to hypothermia. This is mostly because of its co-morbidity with asphyxia, premature birth and severe neonatal infections. Worldwide, neonatal hypothermia case fatality rates (CFRs) range from 8.5% to 52%. This study aimed to assess how well a video-based training intervention on mothers' knowledge and practices in preventing neonatal hypothermia worked. The knowledge and practices of two groups of primi-para mothers-one control group and one intervention group-were compared in order to achieve this. A total of 124 primipara mothers took part in the research. Using a video based tool, the intervention group was educated about preventing hypothermia in newborns. Both control and intervention group mothers were interviewed to compare the knowledge and practices. Sixty-one of the sixty-two mothers in the control group were unsure of which body area to cover in order to preserve the baby's body heat. Following the intervention, 61 out of 62 mothers in the group recognised which body part to cover to protect the baby's body heat. In the post-intervention group, 98.4% of moms wore a cap over their baby's head, compared to just 35.5% in the control group. The results of this study demonstrate the significant improvement in mothers' knowledge and actions about the prevention of neonatal hypothermia resulting from the use of a video-based training tool.

Superior bendability enabled by inherent in-plane elasticity in Bi2Te3 thermoelectrics

With the rapid development of modern wearable electronics, powerful and deformable thermoelectric generators have become an urgent need as the power units that convert environmental or body heat into electricity. Existing efforts mostly focused on the assistance for deformability by substrates/additives, the resultant devices usually output much less power and showed very poor power retainment. Elasticity is inherent to all solids, which therefore offers an intrinsic solution for making thermoelectrics deformable without compromise in power output because of its full recoverability. This work demonstrates this in best-performing (Bi, Sb)2(Te, Se)3 thermoelectrics near room temperature, ending up in the film devices with both extraordinary power density and robust recoverable bendability. This originates from the inherent large elasticity for the in-plane orientation, which is enabled by an easy tape stripping approach for the Van der Waals layered structure, allowing the realization of both powerfulness and bendability that are equally important for wearable thermoelectrics.

Exploring the effect of clothing moisture content on heat and moisture transfer from the human body using a sweating thermal manikin

Evaporative heat loss is an important component of the human body's energy balance and several developed thermal comfort models are available to assess heat and mass transfer during human sweating. However, the impact of sweat-soaked clothing due to human perspiration on heat and moisture transfer from the body remains understudied. In this study, the thermal and moisture properties of typical summer clothing were evaluated and moisture adsorption and desorption curves were obtained. The heat losses of the human body in different sweating states were compared using a sweating thermal manikin. It was found that the clothing moisture content and the clothing coverage ratio had a significant effect on the human body heat loss. As the sweating rate increases, additional resistances of the sweat moisture transfer will be added in the sweat-soaked clothing, which would adversely affect the skin temperature. The results show that the total thermal resistance of fully wetted clothing decreased by an average of almost 30% compared to dry clothing ensembles. To account for such differences, the clothing thermal and evaporative resistance, along with the temperature and vapor pressure at varying moisture contents were evaluated and predicted with empirical equations. This enables integrating a dynamic heat and moisture transfer model for the sweat-soaked clothing into a prevailing thermo-physiological model. Accounting for real clothing physical parameters is vital when evaluating thermal comfort in hot and humid weather conditions.

Compact Vital-Sensing Band with Uninterrupted Power Supply for Core Body Temperature and Pulse Rate Monitoring.

Although wearable devices for continuous monitoring of vital signs have undergone significant advancements, their need for frequent recharging precludes continuous operation, potentially leading to adverse outcomes being overlooked. Additionally, the scattered locations of the sensors hamper wearability. Herein, we present a compact vital-sensing band with uninterrupted power supply designed for continuous monitoring of core body temperature (CBT) and pulse rate. The band─which comprises two sensors, a power source (i.e., a flexible thermoelectric generator (TEG) and a battery), and a flexible circuit─is worn on the forearm. The CBT is calculated by measuring the skin temperature and heat flux, while a triboelectric nanogenerator-based self-powered pressure sensor is utilized for pulse rate monitoring. The TEG is a flexible unit that converts body heat into electricity, accumulating a total energy of 314 mJ (100%). Out of this total energy, only 43.2 mJ (7.2%) is utilized for CBT measurements, while the remaining 270.80 mJ (92.8%) is stored in the battery. This enables reliable and continuous operation of the vital-sensing band, highlighting its potential for use in healthcare applications.

Self-Powered Standalone Performance of Thermoelectric Generator for Body Heat Harvesting

Self-Powered Standalone Performance of Thermoelectric Generator for Body Heat Harvesting

The Effect of Giving Hot-Packs on The Grade of Shivering in Post-Surgery Caesarean Section Patients at Grandmed Hospital Lubuk Pakam

Shivering after anesthesia is a recovery mechanism in the body due to negative side effects such as discomfort and pain due to stretching of the surgical scar, and increased muscle activity following increased oxygen demand. When a client experiences shivering, it is necessary to warm the body with heat therapy given to clients whose temperature is ? 36?C. A hot-pack is a closed package containing gel with a temperature of 40?C. The hot-pack will be given on the right and left inner arms for about 15 minutes. The type of research used is pre-experimental with one group Pre-test and Post-test design. The technique used in sampling in this study is non-probability sampling, in the form of Accidental sampling with a sample size of 20 respondents, while the instrument used in this study is an observation sheet. This study uses univariate and bivariate analysis. In this study, bivariate analysis was carried out using the Paired T-Test. Based on the Statistical Test conducted using the Paired Sample T-test method, the value obtained was p value 0.000 (? <0.05) which means Ho is rejected and Ha is accepted. This means that there is an Effect of Giving Hot-Packs on the Degree of Shivering in Post-Caesarean Section Patients at Grandmed Hospital Lubuk Pakam. This study concludes that giving hot-packs reacts to skin receptors and channels the temperature effect on body heat so that it can reduce shivering.

Low-Cost Hyperelastic Fuller-Dome-Structured Nanocellulose Aerogels by Dual Templates for Personal Thermal Management.

It is critically important to maintain the body's thermal comfort for human beings in extremely cold environments. Cellulose nanofibers (CNF)-based aerogels represent a promising sustainable material for body's heat retention because of their renewability and low thermal conductivity. However, CNF-based aerogels often suffer high production costs due to expensive CNF, poor elasticity and/or unsatisfactory thermal insulation owing to improper microstructure design. Here, a facile dual-template strategy is reported to prepare a low-cost, hyperelastic, superhydrophobic Fuller-dome-structured CNF aerogel (CNF@PU) with low thermal conductivity. The combination of air template by foaming process and ice template enables the formation of a dome-like microstructure of CNF@PU aerogel, in which CNF serves as rope bars while inexpensive polyurethane (PU) acts as joints. The aerogel combines ultra-elasticity, low thermal conductivity (24mW m-1 K-1), and low costs. The as-prepared CNF@PU aerogel demonstrates much better heat retention than commercial thermal retention fillers (e.g., Flannelette and goose down), promising its great commercial potential for massively producing warming garments. This work provides a facile approach for creating high-performance aerogels with tailored microstructure for effective personal thermal management.

Daily Diet and Temporal Variation of Swainson's Hawk Prey Deliveries

ABSTRACT The quantity and timing of prey delivery affect the development of altricial young, can induce trade-offs in parental behavior, and ultimately influence fitness of the young. We investigated the dynamics of prey deliveries in a population of Swainson’s Hawks (Buteo swainsoni) in northern California to better understand its temporal component. We installed 12 motion-triggered cameras in nests between 2013 and 2018, and documented 466 unique prey deliveries. Of those, 455 prey items were identifiable to at least class. Mammals made up the majority of prey in terms of number of deliveries (88.2%) and estimated biomass delivered to the nest (97.1%). Of those, pocket gophers (Thomomys spp.) and voles (Microtus spp.) together made up almost half of the deliveries and biomass. Most prey was delivered to the nest in midday (i.e., 1000–1459 H), suggesting these are important foraging hours for this population. However, afternoon air temperatures in the study area can be high and may require that nestlings be shaded, setting up a potential trade-off between foraging and protecting the nestlings’ thermal homeostasis. Our study provides initial insight into the daily temporal dynamics of prey delivery for one of the latest-breeding raptors in North America.

Mechanically Adaptable High‐Performance p(SBMA‐MMA) Copolymer Hydrogel with Iron (II/III) Perchlorate for Wearable Thermocell Applications

AbstractQuasi‐solid‐state thermocells (QTECs) show promise as a power source for wearable devices by converting body heat into electricity. While significant progress has been made with p‐type elements for QTECs, challenges remain with their n‐type counterparts. Here, a high‐performance n‐type QTEC element is presented, using a copolymer hydrogel that outperforms conventional p‐type elements. This copolymer hydrogel combines hydrophilic zwitterionic sulfobetaine methacrylate (SBMA) for ionic conduction and hydrophobic methyl methacrylate (MMA) for structural stability. By increasing the MMA content from 35 to 100 wt.%, versatile control is achieved over the hydrogel's elastic modulus (72 kPa to 127.7 MPa) and tensile strength (54 kPa to 6.7 MPa). A high mechanical toughness of 7.2 MJ m−3 is also achieved at 68 wt.% MMA. The mechanically robust and high toughness p(SBMA‐MMA) hydrogel is then immersed in Fe(ClO4)2/3 solutions of different concentrations to evaluate its performance as an n‐type QTEC element. The hydrogel with 0.8 M Fe(ClO4)2/3 exhibits a high ionic Seebeck coefficient of −1.7 mV K−1, a power density of 1.1 mW m−2 K−2, and an elastic modulus of 1.6 MPa, which is similar to that of human skin. Finally, the optimized n‐type p(SBMA‐MMA) hydrogels demonstrate the potential application for wearable devices.

A case of acute pulmonary edema caused by exertional heat stroke

This paper reports a case of acute pulmonary edema caused by exertional heat stroke due to imbalance of body heat production and heat dissipation caused by high intensity military training physical activities. The patient's lesions developed rapidly and pulmonary edema progressed rapidly and diffusingly. After early identification, active invasive mechanical ventilation and hormone therapy, the pulmonary imaging lesions of pulmonary edema were rapidly absorbed, and the dyspnea was improved. This article discusses the incidence, imaging features and treatment of acute pulmonary edema caused by exertional heat stroke, and provides reference for clinical diagnosis and treatment.

Microstructured Reflective Coatings on Commodity Textiles for Passive Personal Cooling.

As the effects of climate change become more severe and widespread, maintaining personal thermal homeostasis becomes necessary for survival. In principle, advanced textiles and garments have the ability to leverage light absorption, transmission and/or reflection, in addition to straightforward convection, to heat or cool bodies in extreme temperature conditions. For cooling, in particular, surfaces adept at selectively reflecting or refracting high-energy incident light (200 nm-2.5 mm) from the sun while transmitting or emitting infrared light (8-13 mm) from radiant body heat boast the ability to maintain cooler body temperatures, even when exposed to direct sunlight and the open sky. Here, we present a strategy to transform common clothing into implements for passive personal cooling. As confirmed by Mie scattering calculations, cheap and biocompatible calcium carbonate and barium sulfate micro/nanoparticles are found to serve as suitable reflectors for radiative cooling. Finite-difference time domain simulations reveal, surprisingly, that higher reflectance is achieved with surface coatings containing these materials, as compared to extruded metamaterial fibers containing CaCO3 and BaSO4 particles embedded within a polymer matrix. A stepwise process involving photoinitiated chemical vapor deposition and ion-exchange driven crystal growth is used to create a lamellar composite coating comprised of alternating CaCO3 and BaSO4 nano/microparticle layers directly on the surface of common fabrics. A polyester poplin fabric coated in this manner shows a cooling ability of up to 8 °C compared to an uncoated sample, achieving a maximum cooling of 6 °C below ambient temperature. Wash and durability testing of the lamellar coating reveal no mechanical degradation and no evident attenuation in the material's performance, affirming its resilience and long-term effectiveness as a functional textile coating for personal cooling. We also assess the performance of our coated fabrics in multiple outdoor environments to conclude that we can achieve up to 3.4 °C of sub-ambient cooling in optically complex built environments.

Utilization of Tea Polyphenols as Color Developers in Reversible Thermochromic Dyes for Thermosensitive Color Change and Enhanced Functionality of Polyester Fabrics

Thermochromic textiles possess the capability to indicate ambient temperature through color changes, enabling real-time temperature monitoring and providing temperature warnings for body heat management. In this study, three thermochromic dyes—blue, red, and yellow—were synthesized using crystalline violet lactone (CVL), 6′-(diethylamino)-1′,3′-dimethyl-fluoran (DDF), and 3′,6′-dimethoxyfluoran (DOF) as leuco dyes, respectively, with biomass tea polyphenol serving as the color developer and tetradecanol as the phase change material. The chemical structures of these dyes were characterized using UV spectroscopy, infrared spectroscopy, Raman spectroscopy and 1H NMR. The thermochromic mechanisms were investigated, revealing that the binding bonds between the leuco dyes and the color developer broke and reorganized with temperature changes, imparting reversible thermochromic property. Polyester fabrics were dyed using an impregnation method to produce three reversible thermochromic fabrics in blue, red, and yellow. The structure and properties of these fabrics were analyzed, showing a significant increase in the UPF value from 26.3 to approximately 100, indicating enhanced UV resistance. Water contact angle measurements revealed that the contact angle of undyed polyester fabrics was 139°, while that of dyed polyester fabrics decreased by about 40°, indicating improved hydrophilicity. Additionally, the fabric inductive static tester showed that the static voltage half-life of dyed polyester fabric was less than 1 s, demonstrating a significant antistatic effect. Infrared thermal imaging results indicated that during the warming and cooling process, the thermochromic polyester fabric exhibited specific energy storage and insulation effects at 38 °C, close to the human body temperature. This study presented a novel approach to developing smart color-changing textiles using biomass-derived thermochromic dyes, offering diverse materials for personal thermal management, and intelligent insulation applications.

Assessment of early neonatal practices to prevent hypothermia ; A comparative study

Background Globally, neonatal deaths are significantly attributed to hypothermia. This is mostly because of its co-morbidity with asphyxia, premature birth and severe neonatal infections. Worldwide, neonatal hypothermia case fatality rates (CFRs) range from 8.5% to 52%. This study aimed to assess how well a video-based training intervention on mothers’ knowledge and practices in preventing neonatal hypothermia worked. Methods The knowledge and practices of two groups of primi-para mothers—one control group and one intervention group—were compared in order to achieve this. A total of 124 primipara mothers took part in the research. Using a video based tool, the intervention group was educated about preventing hypothermia in newborns. Both control and intervention group mothers were interviewed to compare the knowledge and practices. Results Sixty-one of the sixty-two mothers in the control group were unsure of which body area to cover in order to preserve the baby’s body heat. Following the intervention, 61 out of 62 mothers in the group recognised which body part to cover to protect the baby’s body heat. In the post-intervention group, 98.4% of moms wore a cap over their baby’s head, compared to just 35.5% in the control group. Conclusion The results of this study demonstrate the significant improvement in mothers’ knowledge and actions about the prevention of neonatal hypothermia resulting from the use of a video-based training tool.

Flexible polyester-embedded thermoelectric device with Bi2Te3 and Te legs for wearable power generation

This study presents an approach for powering wearable sensors by integrating nanostructured bismuth telluride (Bi2Te3 and Te legs) into flexible polyester substrates. The choice of polyester as the substrate is because it is widely used in clothing, especially in items such as shirts, blouses, dresses, and sportswear. This enables seamless integration with wearable devices. By capturing wasted body heat, our small and flexible thermoelectric generators (TEGs) offer long-term operation without the need to plug the batteries. We demonstrate the feasibility of using commercially available polyester for reproducible electrochemical deposition of highly oriented Bi2Te3 and Te material. Through electrodeposition, we embed Bi2Te3 and Te legs within the flexible polyester, creating a cost-effective and easily scalable hybrid system for wearable energy harvesting.Our optimized TEG design, which can be worn on the arm or forehead, achieves impressive power density compared to existing state-of-the-art solutions. With a mere 3.5 °C temperature difference, only two pairs of p- and n-type legs, and a thickness of approximately 15 µm, our TEG generates a maximum open circuit voltage of ∼0.1 mV and a maximum power density of ∼0.04 mW·K-1·cm−2. With 250 pairs, 10 mV can be reached. This cost-effective design also integrates electrical contacts, surpassing previous flexible TEG performances. These advancements make our TEGs suitable for driving microwatt-level electronic sensors and open new avenues for efficient energy harvesting in wearable applications.

Body heat energy driven knitted thermoelectric garments with personal cooling

Wearable, thermoelectric (TE) devices have gained significant interest in recent years as they can both generate output power from converting body heat into electrical energy and be utilized in personal cooling through the Peltier effect. Currently, researched wearable TE cooling devices focus on devices that can be attached to the human body in specific locations and use heat sinks or elongated thermoelectric pillars to increase their effectiveness, making them hard and bulky. In addition, these devices are attached, not integrated, to wearable garments, making their manufacturing a multi-step process. To address this issue, we developed a knitted TE garment through a single-step manufacturing process that offers energy generation and personal cooling capabilities. The functioning of the cooling device was mathematically modelled and analyzed to understand its scalability, optimization, and to show its potential. This garment features excellent thermoelectric generation of 7.48 mV and 0.46 mA on the human body, and the ability to cool the human body up to 1.5 °C. The observations proved that the mathematical model could predict the behavior of the TE device closely. The results showed that the proposed method of knitted TE cooling garment manufacturing is a viable and scalable process.

Preferences for drinking water temperature in mice vary with ambient temperature.

Temperature detection and temperature preference are critical for the maintenance of thermal homeostasis and protection from noxious temperature. Methods to measure the time spent on plates of different temperatures such as the two-plate test and thermal-gradient test are generally used to evaluate temperature preference. In this study, we established a temperature preference test that assesses water drinking behavior by modifying the two-bottle taste preference test. We found that mice in a common-temperature environment of 23 °C avoid drinking water more than 40 °C. While mice in a common-temperature environment preferred 10 °C and 30 °C water equally, mice in a hot environment at 35 °C preferred to 10 °C water compared to 30 °C water. Moreover, mice in a cold environment of 10 °C did not avoid drinking 40 °C water compared to 10 °C water. From these results, the temperature preference test that we developed could be used to evaluate temperature preference owing to the ambient temperature changes.

Thermogalvanic hydrogel with controllable ion confined transportation and its application for self-powered lactic acid sensor

Low-grade heat energy (below 100 °C) is abundantly available in the natural environment, yet effective utilization remains challenging. Liquid-state thermocells, also known as thermo-electrochemical cells or thermogalvanic cells, have emerged as promising solution for converting low-grade heat into electrical energy due to their high Seebeck coefficients (mV·K–1). However, traditional liquid-state thermocells suffer from the issue of liquid leakage caused by frequent cooling or heating during operation. Here in this work, we propose thermogalvanic hydrogels through introducing redox ions into hydrogel framework. The thermoelectric performance of the proposed hydrogel is highly dependent on the ion concentration, which is attributed to the confined ion transportation in micro/nano channels caused by the salting out effect. After the optimization of thermoelectric parameters, a Π-shaped thermocell composed of three p-n pairs is fabricated to harvest low-grade body heat energy. An open-circuit voltage of 163 mV, a short-current density of 0.7 mA·m–2 and a maximum power density of 26.7 μW·m–2 are achieved at a temperature difference of 30 K. To further demonstrate the practical potential, the thermoelectric generator is integrated with a lactic acid sensor to sensitively detect the lactic acid concentration without any external power supplies.

Interfacial engineering of flexible Ag2-xSnxS on carbon fabric for enhanced wearable thermoelectric generator

Smart wearable devices are still powered by batteries requiring constant recharging, which is a key challenge faced in wearable technologies. Fabrication of flexible thermoelectric materials that can utilize body heat for wearable applications are an attractive alternative to batteries. Developing a thermoelectric material that is flexible, affordable, and has good performance remains a considerable challenge owing to the constrained thermoelectric efficiency of conducting polymers and the inherent rigidity of inorganic materials. Here, we have used a solvothermal technique to incorporate Ag2-xSnxS into conductive carbon fabric as a flexible thermoelectric material. To further enhance its thermoelectric performance, various concentrations of Ag2-xSnxS are grown on carbon fabric. The monoclinic phase of Ag2S on carbon fabric was verified by XRD analysis. After analyzing the thermoelectric characteristics of Ag1.84Sn0.16S, a maximum power factor of 110 μW/mK2 was observed for the SSS8 sample. This value is four times higher than the percentage of pristine Ag2S-CF. The W-TEG device fabricated using 3 pair modules produced an output voltage ranging from 0.09 to 1.5 mV across a temperature gradient of 3 to 8 K.

Analysis of variables in finite element analysis for multi-pass welding in nuclear power plant components, part 1: Comprehensive study with experimental validation using scientific weld specimen

The influence of various parameters in welding simulations using finite element analysis (FEA) was investigated in this study. Welding experiments and finite element simulations were conducted to analyze residual stress and post-welding distortion. It was a specially designed V-groove specimen, filled with bead passes using Gas Tungsten Arc Welding (GTAW), that facilitated the measurement of distorted shapes and residual stress. Advanced measurement techniques, including three-dimensional laser scanning and the contour method, were used to capture detailed data on the welded specimen. Three different heat source models (body heat flux, temperature boundary, and Goldak's double-ellipsoidal model) were employed in the simulations, and their effect on residual stress distributions was analyzed. Additionally, the effects of hardening models, bead deposition methods, bead shape modeling, welding sequences, and lumping of weld passes on simulation were systematically analyzed. The findings suggest that a combined approach using different modeling techniques and careful calibration of parameters can enhance the reliability of simulations in predicting weld residual stress and distortions.