Converting body heat into electricity is a promising strategy for supplying power to wearable electronics. To avoid the limitations of traditional solid-state thermoelectric materials, such as frangibility and complex fabrication processes, we fabricated two types of thermogalvanic gel electrolytes with positive and negative thermo-electrochemical Seebeck coefficients, respectively, which correspond to the n-type and p-type elements of a conventional thermoelectric generator. Such gel electrolytes exhibit not only moderate thermoelectric performance but also good mechanical properties. Based on these electrolytes, a flexible and wearable thermocell was designed with an output voltage approaching 1 V by utilizing body heat. This work may offer a new train of thought for the development of self-powered wearable systems by harvesting low-grade body heat.
Sustainable electrical potential of tens of millivolts can be induced by water vapor adsorption on a piece of porous carbon film that has two sides with different functional group contents. Integrated experiments, and Monte Carlo and ab initio molecular dynamics simulations reveal that the induced potential originates from the nonhomogeneous distribution of functional groups along the film, especially carboxy groups. Sufficient adsorbed water molecules in porous carbon facilitate the release of protons from the carboxy groups, resulting in a potential drop across the carbon film because of the concentration difference of the released free protons on the two sides. The potential utilization of such a phenomenon is also demonstrated by a self-powered humidity sensor.
Converting body heat into electricity is a promising strategy for supplying power to wearable electronics. To avoid the limitations of traditional solid-state thermoelectric materials, such as frangibility and complex fabrication processes, we fabricated two types of thermogalvanic gel electrolytes with positive and negative thermo-electrochemical Seebeck coefficients, respectively, which correspond to the n-type and p-type elements of a conventional thermoelectric generator. Such gel electrolytes exhibit not only moderate thermoelectric performance but also good mechanical properties. Based on these electrolytes, a flexible and wearable thermocell was designed with an output voltage approaching 1 V by utilizing body heat. This work may offer a new train of thought for the development of self-powered wearable systems by harvesting lowgrade body heat.Given the recent developments in the area of wearable electronics and e-skins, [1][2][3][4][5][6] the emerging need for selfpowered energy supply has heightened the interest in energy harvesting from the environment or human beings. Among recognized energy-harvesting technologies, such as solar cells [7,8] and triboelectric and electret generators, [9,10] thermal energy is a potential power source that is widely available in the environment and in industrial processes. [11,12] However, human bodies are also a permanent heat source, with a surface temperature of about 32 8C and possibly tens of degrees temperature difference between the human body and its environment. [13,14] Hence, it is of practical meaning to convert body heat energy, a type of low-grade heat, into electricity for directly powering wearable electronics. [15][16][17] The most convenient strategy to utilize low-grade heat is thermal-electric conversion. Traditional thermoelectric generators utilizing the Seebeck effect are mainly based on solidstate semiconductors or conducting polymers, [18,19] with output voltages limited by the relatively low Seebeck coefficient (several hundreds mV K À1 ). Meanwhile, the frangibility and expensiveness of thermoelectric materials as well as their complicated fabrication processes are other obstacles restricting their application in wearable electronics. [20] Alternatively, a large thermovoltage can be derived from thermogalvanic effects, resulting from temperature-dependent entropy changes during electron transfer between redox couples and electrodes. [21][22][23][24] Previous reports mainly focused on the exploration of electrode materials, such as carbon nanotubes (CNTs) and graphene, [25][26][27][28] to achieve high thermal-electric conversion efficiencies. However, because of the aqueous electrolytes used in thermocells, large-scale integration and packaging of the units would be more difficult in applications, especially for wearable devices. [29] Inspired by the successful application of gel electrolytes in solid-state electrochemical energy storage systems and stretchable ionic conductors, [30][31][32][33] we surmised that solid-state or quasi-solidstate gel...
Adsorption-driven heat pumps (AHPs) based on metal–organic frameworks (MOFs) have been garnering rapidly growing research interests due to their outstanding adsorption performance.
BackgroundAcute diarrhea is a leading cause of morbidity and mortality in children, particularly in those under the age of 5 years. Rotavirus is recognized as the leading cause of acute diarrhea in children, however, the contribution of bacterial pathogens as causative agents varies throughout the world. Here we report a hospital-based prospective study to analyze the characteristics of bacterial pathogens associated with acute diarrhea in children under 5 years of age.MethodsStool samples were collected from 508 patients with acute diarrhea under 5 years of age who presented at our hospital. Nine pathogens were isolated and identified by culturing, serology or PCR, these included Salmonella spp., Shigella spp., Vibrio cholerae, diarrheagenic Escherichia coli (DEC), Aeromonas spp., Plesiomonas spp., Vibrio parahaemolyticus, Campylobacter spp. and Yersinia enterocolitica. Antimicrobial sensitivity tests of these pathogens were conducted. The most commonly detected pathogen, Salmonella spp., was further investigated by PCR and sequencing of antibiotic resistance-related genes.ResultsPathogens were identified in 20.1 % of the 508 samples. The most commonly detected pathogens were Salmonella spp. (8.5 %), followed by DEC (4.7 %), Campylobacter jejuni (3.0 %) and Aeromonas spp. (2.0 %). The resistance rates to ampicillin and tetracycline in Salmonella spp. were >60 %, but were <30 % to cephalosporins and quinolones. More than 50 % of DEC strains displayed resistance to ampicillin, cefotaxime and tetracycline, and 60 % of C. jejuni strains were resistant to ciprofloxacin but highly sensitive to the other antibiotics. Among 12 cephalosporin-resistant Salmonella isolates, TEM-1 and CTX-M-14 determinants were present in two (16.7 %) isolates. PCR screening for plasmid-mediated quinolone resistance genes revealed gyrA mutations in one of three highly quinolone resistant isolates.ConclusionsSalmonella spp., DEC, Campylobacter spp. and Aeromonas spp. were the most commonly detected bacterial pathogens in children under the age of 5 years with acute diarrhea. Our findings indicate that ampicillin and tetracycline are not suitable as first line therapeutic drugs against Salmonella spp. Resistance to third generation cephalosporins and quinolones was also detected. TEM-1 and CTX-M-14 genetic determinants, and gyrA mutations, were the major mechanisms associated with high levels of cephalosporin and quinolone resistance, respectively, in Salmonella isolates.
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