•A novel structural design of the wearable TEG to harvest body heat is developed.•The TEG features excellent flexibility and high power generation for body heat harvesting.•A miniaturized ...accelerometer is powered by the TEG to detect body motion through harvesting wrist heat.
Wearable thermoelectric generators (TEGs) enable the conversion of human body heat into microwatts to milliwatt electricity, which can be utilized to power miniaturized electronic devices for motion detection and healthcare monitoring. This paper presents a novel wearable TEG with 52 pairs of cubic-shaped thermoelectric legs to harvest human body heat. The thermoelectric legs are made of P-type and N-type Bi2Te3-based powder materials, and are connected electrically in series through soldering. The flexible printed circuit board (FPCB) with special holes is designed and used as substrate to enhance the flexibility of the TEG for wearable applications. The performances of the TEG, including the bulk thermoelectric legs, are characterized. The results show that the TEG can generate an open-circuit voltage of 37.2 mV at ΔT = 50 K, and the internal resistance of the TEG is quite low at a value of 1.8 Ω. Then the TEG was worn on a human wrist to harvest body heat and power a 3-axis miniaturized accelerometer for detection of body motion at ΔT = 18 K. The results demonstrate that the developed wearable TEG features high output performance and could be utilized for powering electronics and/or sensors by harvesting human body heat.
This paper introduces a novel method for characterizing the oxygen vacancy associates in hydrogenation-modified TiO2 by using a positron annihilation lifetime spectroscopy (PALS). It was found that a ...huge number of small neutral Ti3+–oxygen vacancy associates, some larger size vacancy clusters, and a few voids of vacancy associates were introduced into hydrogenated TiO2. The defects blurred the atomic lattice high-resolution transmission electron microscopy (HRTEM) images and brought about the emergence of new Raman vibration. X-ray photoelectron spectroscopy (XPS) measurement indicated that the concentration of oxygen vacancies was 3% in the TiO2 lattice. The photoluminescence (PL) spectroscopy, photocurrent, and degradation of methylene blue indicated that the oxygen vacancy associates introduced by hydrogenation retarded the charge recombination and therefore improved the photocatalytic activity remarkably.
This paper presents a flexible capacitive tactile sensor array embedded with a truncated polydimethylsiloxane pyramid array as a dielectric layer. The proposed sensor array has been fabricated with 4 ...× 4 sensor units. The measurement ranges of forces in the x-axis, y-axis, and z-axis are 0-0.5, 0-0.5, and 0-4 N, respectively. In the range of 0-0.5 N, the sensitivities of the sensor unit are 58.3%/N, 57.4%/N, and 67.2%/N in the x-axis, y-axis, and z-axis, respectively. In the range of 0.5-4 N, the sensitivity in the z-axis is 7.7%/N. Three-axis force measurement has been conducted for all the sensor units. The average errors between the applied and calculated forces are 11.8% ± 6.4%. The sensor array has been mounted on a prosthetic hand. A paper cup and a cube are grasped by the prosthetic hand and the three-axis contact force is measured in real time by the sensor array. Results show that the sensor can capture the three-axis contact force image both in light and tight grasping. The proposed capacitive tactile sensor array can be utilized in robotics and prosthetic hand applications.
Methanol steam reforming (MSR) is an attractive option for in-situ hydrogen production and to supply for transportation and industrial applications. This paper presents a novel thermally autonomous ...MSR microreactor that uses silicon carbide (SiC) honeycomb ceramic as a catalyst support to enhance energy conversion efficiency and hydrogen production. The structural design and working principle of the MSR microreactor are described along with the development of a 3D numerical model to study the heat transfer and fluid flow characteristics. The simulation results indicate that the proposed microreactor has a significantly low drop in pressure and more uniform temperature distribution in the SiC ceramic support. Further, the microreactor was developed and an experimental setup was conducted to test its hydrogen production performance. The experimental results show that the developed microreactor can be operated as thermally autonomous to reach its target working temperature within 9 min. The maximum energy efficiency of the microreactor is 67.85% and a hydrogen production of 316.37 ml/min can be achieved at an inlet methanol flow rate of 360 μl/min. The obtained results demonstrate that SiC honeycomb ceramic with high thermal conductivity can serve as an effective catalyst support for the development of MSR microreactors for high volume and efficient hydrogen production.
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•A novel methanol steam reforming microreactor using silicon carbide honeycomb ceramic is proposed.•The methanol steam reactor microreactor has low pressure drop (<1.2 Pa) and short startup time (<9 min).•The energy efficiency of the microreactor is 67.85% at methanol conversion of 86.78%.
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•A curing depth prediction model based on Jacob’s working curve was established.•Correction factor n was introduced to correct critical curing energy.•Printing process was ...quantitatively monitored through the degree of conversion of functional group and photopolymer opto-rheological properties.•A method for quick-selection of printing parameters was proposed and verified, and the final printing accuracy reached 12 μm.
Vat photopolymerization is a widely employed additive manufacturing (AM) technique that commonly applying a digital light processing (DLP) light engine to provide a patterned light source. Notably, printing extreme-size structures is challenging, and the selection of printing parameters was currently highly reliant on repeatable trial-and-error experiments. In this work, a theoretical model for curing depth prediction was established by observing the effect of light intensity. A correction factor n was introduced to optimize the relationship among the critical curing energy, exposure time, and light intensity. Forming experiments verified the accuracy of the proposed theoretical curing depth prediction model, and a correction factor n equal to 0.75 was obtained. Optical rheological characterization experiments and Fourier transform infrared spectroscopy (FTIR) supported the quantitative characterization of the DLP printing process while revealing a stepwise transition during photocuring. Finally, a guidance for quick selection of the optimal curing time for 3D structure was obtained and applied to the high-precision microstructure printing process. High-fidelity microneedle arrays with 12 μm details were printed. This method of rapid selection of printing parameters and printing microstructures with high-precision details can potentially be used in the field of 3D bioprinting.
N-doped biochar as adsorption material for heavy metal removal has attracted increasing concern in environmental application due to its unique features. Here, N-doped biochar was prepared by ...hydrothermal carbonization of
Camellia sinensis
branch waste using KOH/NH
4
Cl at 120–280 °C for 2 h under 0.4–6.5 MPa, followed by structural analysis. The results showed that the highest N content determined by elemental analysis could reach up to 6.18% in biochar, and the major N species were involved in graphitic N, pyrrolic N, and pyridinic N. Interestingly, these N-doped biochar exhibited the effective adsorption ability of Cu
2+
, Pb
2+
, Zn
2+
, and Cr
6+
. The batch adsorption behavior had a better adjustment to the pseudo-second-order kinetic and the Langmuir adsorption isotherm models. In brief, the present results are attributed to develop low-cost adsorbent for removing heavy metal ions.
Seawater intrusion has a serious impact on industry, agriculture, and people's daily life. Thus, the present study was designed to elucidate the pollution sources and groundwater evolution in typical ...intrusion areas of Shandong Province by hydrochemistry and environmental isotope techniques. The water samples were collected to analyze the groundwater evolution under different intrusion, and groundwater evolution in the south of Laizhou Bay from 2005 to 2019. The findings indicated that the groundwater level dropping funnel caused by overexploitation was the direct causation of seawater intrusion in the three typical intruded areas. The groundwater evolution paths demonstrated that the groundwater in the south of Laizhou Bay had the fastest evolution rate and the highest degree of evolution, followed by the Dagu River Basin. The groundwater evolution extent and fitting of mixing lines indicated that the groundwater in the south of Laizhou Bay, Longkou, and Dagu River Basin was dominated by palaeosaltwater intrusion, modern seawater intrusion, and sea-saltwater mixed intrusion, respectively. Palaeosaltwater mixing produces a more severe salinization effect compared to seawater mixing. Meanwhile, the isotopes are gradually enriched with the deepening of intrusion, while the decrease of isotopes is delayed compared with the saltwater retreat. This is caused by that the stable isotopes enriched in the aquiclude due to the chemical permeation effect will be released into the aquifer after the salinity attenuates in the aquifer. The palaeosaltwater intrusion caused by anthropogenic activities has promoted serious fluorine pollution in the south of Laizhou Bay, while the groundwater nitrate pollution in Longkou was the most serious, followed by the Dagu River Basin due to high-density agricultural and domestic activity.
Radon (222Rn) has been widely employed as a tracer for estimating submarine groundwater discharge (SGD). However, the uncertainty of the SGD estimation remains significant, due to the spatial ...variability of radon in groundwater. In this study, we analyzed the hydrochemical properties of seawater and coastal groundwater in the Upper Gulf of Thailand and discussed the distribution characteristics of 222Rn in aquifers in terms of aquifer lithology, groundwater system recharge conditions, and water retention time. The results suggested that the residence time of groundwater and the process of groundwater salinization have the greatest impact on the distribution of 222Rn activity. A 222Rn mass balance model, synthesizing the distribution characteristics of 222Rn in groundwater and tidal influences on SGD, was built to estimate the submarine groundwater discharge in the Upper Gulf of Thailand. The result showed that the SGD flux of the Upper Gulf of Thailand was 0.0203 m/d. Moreover, there is a positive correlation between tidal height and the activity of 222Rn in groundwater. The SGD observed during the low tide was about 1.25 times higher than that observed during the high tide. This may influence the marine geochemical cycles of elements and their impact on marine ecosystems.
Proton exchange membrane fuel cells (PEMFCs) have been utilized as a promising power source for new energy vehicles. Their performances are greatly affected by the structural design of the flow field ...in the bipolar plate. In this paper, we present a novel three-dimensional (3D) bionic cathode flow field, inspired by the small intestinal villi. The structural design and working principle of the 3D bionic flow field units are first described. A 3D numerical model is developed to study the mass transfer and distribution of the reactants and products, as well as the polarization performances of the PEMFC with the 3D bionic cathode flow field. The simulation results indicate that the proposed 3D bionic flow field can significantly improve the reaction gas supply from the flow field to porous electrodes, and thus would be beneficial for the removal of liquid water in the cathode. The mass transfer of gas in the PEMFC can be enhanced due to the increasing contact areas between the gas diffusion layer (GDL) and the cathode flow field, and the distribution of currents in the membrane would be more uniform. The obtained results demonstrated the feasibility of using the 3D bionic flow field for the development of highly efficient PEMFCs with high power density.
Superhydrophobic coatings have increasingly become the focal point of research due to their distinctive properties like water resistance, wear resistance, and acid-base resilience. In pursuit of ...maximizing their efficiency, research has primarily revolved around refining the fabrication process and the composition of emulsion/nanoparticle coatings. We innovatively devised a superhydrophobic coating by employing a spraying technique. This involved integrating a γ-Methacryloyloxypropyltrimethoxysilane (KH570)-modified ZrO2/SiO2/silicone-modified acrylic emulsion. A comprehensive evaluation of this coating was undertaken using analytical instruments such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and confocal laser scanning microscopy (CLSM). The coating demonstrated exceptional performance across a range of tests, including wear, immersion, and anti-icing cleaning, showcasing notable wear resistance, sodium chloride corrosion resistance, self-cleaning efficiency, and thermal stability. In particular, one coating exhibited super-hydrophobic properties, with a high contact angle of 158.5 degrees and an impressively low rolling angle of 1.85 degrees. This remarkable combination of properties is attributed to the judicious selection of components, which significantly reinforced the mechanical strength of the coating. These enhancements make it highly suitable for industrial applications where self-cleaning, anti-icing, and anti-contamination capabilities are critical.
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