In this paper, we reported the mechanism of a bimodal Weibull distribution for TDDB of gate dielectric in GaN MISHEMT. It is shown that the properties of traps in the dielectric layer would have a great influence on the long time reliability and life time prediction process.
Spatiotemporal recognition of multiple mechanical stimuli is essential for electronic skin (e-skin), which can provide more complete and accurate interaction information to enable elaborated functions, such as gesture recognition, object manipulation, and fine tactile discrimination. However, nonspecific sensor response and performance sacrifice for integration limit the perceptual capability of the current systems. Here, we report a bioinspired e-skin that can measure strain, shear and pressure independently with direction information using three-dimensional integrated, mechanically isolated multiple sensors. Novel microstructures of collapsed nanocone clusters, hemi-ellipsoids, and wrinkles are introduced in different sensors to achieve a gauge factor of 6 with a linear working range of 80% (linearity > 0.99) for strain, a sensitivity of 0.1 N−1 for shear force, and a sensitivity of 3.78 kPa−1 for pressure, and all of these sensors possess short response times on the order of 100 ms. The independent, highly sensitive, and fast response of these sensors makes real-time recording and mapping of multiple mechanical stimuli to be achieved. Multi-touch gesture recognition and perception of a red bean (0.065 g) in the hand are demonstrated to illustrate the potential applications in wearables, robotics and bionic prostheses.
A new type of solar active carbon-doped Bi3O4Br catalyst was synthesized by combining hydrothermal and post-thermal treatment. The activity of the material under sunlight and visible light was 3.3 times and 2.7 times that of Bi3O4Br, respectively. The C-doping on Bi3O4Br nanosheets increased the built-in electric field strength, thus significantly promoted the migration of charge carriers and enhanced the photocatalytic activity. In addition, replacing Br with C with a smaller atomic radius can shorten the interlayer spacing, which is beneficial to carrier separation. Experiments showed that the doping of C shortened the semiconductor band gap by 9.8% and expanded the absorption range of visible light. Among the photogenerated reactive species, h+ played a major role in the degradation of 1-methylpyrene (a typical polycyclic aromatic hydrocarbons), followed by O2∙- and •OH. Based on intermediate analysis and DFT calculation, we proposed the degradation mechanism and pathways. Quantitative structure–activity relationship (QSAR) analysis showed that some toxic intermediates were produced during the photocatalysis process, but the overall environmental risk was greatly reduced. This work provides new perspective for understanding non-metallic doping in semiconductor photocatalysts to enhance the built-in electric field, and this technology can be extended to other semiconductor materials.
In bioaugmented wastewater treatment systems, it is essential for recalcitrant pollutant-degrading bacteria to form biofilms. Inducing biofilm formation in these bacteria, however, is challenging as it involves multiple inter-related regulating pathways and environmental factors. Herein, we report the remarkable promoting effect of Ca2+ on biofilm formation of two novel pyridine-degrading bacteria with poor innate biofilm-forming capabilities, Pseudomonas sp. ZX01 and Arthrobacter sp. ZX07. The roles of Ca2+ in different biofilm development stages were investigated. Our data showed strong influences of Ca2+ on the initial attachment of the two strains onto positively charged glass surfaces by altering cell surface charge as well as the cation bridging effect. Contrary to many other biofilm promoting mechanisms, Ca2+ downregulated the extracellular polymeric substances (EPS) production per cell in both Pseudomonas sp. ZX01 and Arthrobacter sp. ZX07, while increasing biofilm biomass. This is attributed to the strong cationic bridging between Ca2+ and EPS which can elevate the efficiency of the extracellular products in binding bacterial cells. Furthermore, Ca2+ increased the protein-to-polysaccharide (PN/PS) ratio in biofilm EPS of both strains, which favored cell aggregation, and biofilm establishment by increasing the hydrophobicity of cell surfaces. More intriguingly, the intracellular c-di-GMP, which can drive the switch of bacterial lifestyle from planktonic state to biofilm state, was also elevated markedly by exogenous Ca2+. Taken together, these results would be of guidance for applying the two strains into bioaugmented biofilm reactors where Ca2+ supplement strategy can be employed to facilitate their biofilm formation on the surfaces of engineering carriers.
Fluid immobilizations in tight formations augment the importance of CO2 molecular diffusions in the processes of geological carbon utilization and storage. This study, for the first time, investigates the CO2 diffusions in unconventional tight formations which are saturated with in-situ gas-dissolved pore fluids, both experimentally and theoretically. A novel high-pressure high-temperature diffusion cell was designed to reproduce the actual CO2 diffusions in extremely low-permeability on-site geological cores saturated with methane-dissolved crude oils at the reservoir conditions and various scenarios (e.g., different gas–liquid ratios). On the other hand, a comprehensive mathematical model, which consists composition and diffusion models, was developed for quick predictions and in-depth evaluations. The CO2 diffusion coefficients at the pressure of 18.5 MPa and temperature of 80 °C with varying gas–liquid ratios were obtained from a genetic algorithm-fitting of the measured and calculated data. With the gas–liquid ratios increasing from 0 to 40 sm3/m3, the CO2 diffusion coefficient was found to decrease from 7.90 × 10−9 to 3.09 × 10−9 m2/s and the average velocity of diffusion front reduced from 0.0121 to 0.0050 m/d. This finding indicates methane dissolutions into the crude oil at the reservoir conditions would be detrimental for the CO2 diffusions. Hence, the methane amount is suggested to be well controlled in the processes of geological carbon storage and utilization for oil production. This study will support the foundation of more general application pertaining to geological CO2 utilization and storage, especially in the unconventional tight or shale oil reservoirs.
Biological nervous systems evolved in nature have marvelous information processing capacities, which have great reference value for modern information technologies. To expand the function of electronic devices with applications in smart health monitoring and treatment, wearable energy-efficient computing, neuroprosthetics, etc., flexible artificial synapses for neuromorphic computing will play a crucial role. Here, carbon nanotube-based ferroelectric synaptic transistors are realized on ultrathin flexible substrates via a low-temperature approach not exceeding 90 °C to grow ferroelectric dielectrics in which the single-pulse, paired-pulse, and repetitive-pulse responses testify to well-mimicked plasticity in artificial synapses. The long-term potentiation and long-term depression processes in the device demonstrate a dynamic range as large as 2000×, and 360 distinguishable conductance states are achieved with a weight increase/decrease nonlinearity of no more than 1 by applying stepped identical pulses. The stability of the device is verified by the almost unchanged performance after the device is kept in ambient conditions without additional passivation for 240 days. An artificial neural network-based simulation is conducted to benchmark the hardware performance of the neuromorphic devices in which a pattern recognition accuracy of 95.24% is achieved.
High-speed flexible circuits are required in flexible systems to realize real-time information analysis or to construct wireless communication modules for emerging applications. Here, we present scaled carbon nanotube-based thin film transistors (CNT-TFTs) with channel lengths down to 450 nm on 2-mu m-thick parylene substrates, achieving state-of-the-art performances of high on-state current (187.6 mu A mu m(-1)) and large transconductance (123.3 mu S mu m(-1)). Scaling behavior analyses reveal that the enhanced performance introduced by scaling is attributed to channel resistance reduction while the contact resistance (180 +/- 50 k omega per tube) remains unchanged, which is comparable to that achieved in devices on rigid substrates, indicating great potential in ultimate scaled flexible CNT-TFTs with high performance comparable to their counterparts on rigid substrates where contact resistance dominates the performance. Five-stage flexible ring oscillators are built to benchmark the speed of scaled devices, demonstrating a 281 ps stage delay at a low supply voltage of 2.6 V. High-speed flexible circuits are essential in flexible systems for real-time information analysis and wireless communication. Here, flexible circuits are reported with a 281 ps stage delay based on scaled carbon nanotube thin film transistors.
Periodate (PI)-based advanced oxidation process has recently attracted great attention in the water treatment processes. In this study, solar irradiation was used for PI activation to disinfect waterborne bacteria. The PI/solar irradiation system could inactivate Escherichia coli below the limit of detection (LOD, 10 CFU mL–1) with initial concentrations of 1 × 106, 1 × 107, and 1 × 108 CFU mL–1 within 20, 40, and 100 min, respectively. •O2– and •OH radicals contributed to the bacterial disinfection. These reactive radicals could attack and penetrate the cell membrane, thereby increasing the amount of intracellular reactive oxygen species and destroying the intracellular defense system. The damage of the cell membrane caused the leakage of intracellular K+ and DNA (that could be eventually degraded). Excellent bacterial disinfection performance in PI/solar irradiation systems was achieved in a wide range of solution pH (3–9), with coexisting humic acid (0.1–10 mg L–1) and broad solution ionic strengths (15–600 mM). The PI/solar irradiation system could also efficiently inactivate Gram-positive Bacillus subtilis. Moreover, PI activated by natural sunlight irradiation could inactivate 1 × 107 CFU mL–1 viable E. coli below the LOD in the river and sea waters with a working volume of 1 L in 40 and 50 min, respectively. Clearly, the PI/solar system could be potentially applied to disinfect bacteria in water.
