Abstract Natural wood possesses a unique 3D microstructure containing hierarchical interconnected channels along its growth direction. This study reports a facile processing strategy to utilize such structure to fabricate carbon/silicone composite based flexible pressure sensors. The unique contribution of the multichannel structure on the sensor performance is analyzed by comparing the pressure response of the vertically cut and horizontally cut composite structures. The results show that the horizontally cut composite based sensors exhibit much higher sensitivity (10.74 kPa −1 ) and wider linear region (100 kPa, R 2 = 99%), due to their rough surface and largely deformable microstructure. Besides, the sensors also show little hysteresis and good cycle stability. The overall outstanding sensing properties of the sensors allow for accurate continuous measurement of human pulse and respiration, benefiting the real‐time health signal monitoring and disease diagnoses.
Wet etching of silicon carbide typically exhibits poor etching efficiency and low aspect ratio. In this study, an etching structure that exploits anisotropic charge carrier flow to enable high-throughput, external-bias-free wet etching of high-aspect-ratio SiC micro/nano-structures is demonstrated. Specifically, by applying a catalytic metal coating at the bottom surface of a SiC wafer while introducing patterned ultraviolet light illumination from its top surface, spatial charge separation across the wafer is achieved, i.e., photogenerated electrons are channeled to the bottom to participate in the reduction reaction of an oxidant in the etchant solution, while holes flow to the top to trigger oxidation of SiC and subsequent etching. Such design largely suppresses recombination-induced charge losses, and when used in combination with a top metal catalyst mask, the structure yields a remarkable vertical etching rate of 0.737 µm min-1 and an aspect ratio of 3.2, setting new records for wet-etching methods for SiC.
Sensors are one of the foundations of the modern Internet of Things (IoT) with enormous demand and widely distributed, but most of them rely on power to work independently. To continuously and conveniently power the sensor, a rapid development of self-powered sensors has occurred in recent years. Some existing sensors are fabricated to be small, have long transmission distances and do not require any external power supply. However, the harsh and complex processes for processing such sensors are not beneficial to their universal availability. Therefore, in this work, a laser-induced graphene-based self-powered wireless sensor is proposed. This sensor is fabricated by the facilely and efficient laser processing method, and can harvest external energy, detect the direction of moving objects and sensing simultaneously. It shows great potential in infrastructure monitoring, wearable electronic, smart home, etc.
Directional liquid transport has significant domestic and industrial applications. Tapered objects have theoretically and experimentally been demonstrated to have the ability to spontaneously transport liquids. However, the transporting distance is limited, and consecutively and spontaneously transporting liquids has always been a challenge. In this work we proposed to exploit ladderlike tapered pillars, which are inspired by relay races, to increase the transport distance. These pillars were designed using a developed numerical model and fabricated by a novel alternating etching and coating method followed by wettability enhancement. We demonstrated through experiments that the resulting pillars could consecutively and spontaneously transport a liquid droplet at an average velocity of 0.139 m/s with a maximum acceleration of 5 g. The optimum window of the tilt angle range (0°-25°), contact angle (50°), and the chemical modification time (5 min) were obtained. Such ladderlike tapered pillars are able to improve the water-collection efficiency. These results may provide a new and systematic way to design and fabricate materials and structures for directional liquid transport.
Advanced carbon materials have played an important function in the field of energy conversion and storage. The green and low-carbon synthesis of elemental carbon with controllable morphology and microstructure is the main problem for carbon materials. Herein, we develop a green and low-carbon method to synthesize porous carbon by reacting CO2 with LiAlH4 at low temperatures. The starting reaction temperatures are as low as 142, 121, and 104 °C for LiAlH4 reacting with 1, 30, and 60 bar CO2, respectively. For the elemental carbon, the porosity of elemental carbon gradually decreased, whereas its graphitization degree increased as the CO2 pressure increased from 1 bar to 60 bar. CO2 serves as one of the two reactants and the CO2 pressure can adjust the thermodynamic and kinetic properties of the formation reaction for synthesizing elemental carbon. The mechanism for CO2 pressure-dependent microstructure and morphology of carbon is discussed on the basis of the formation reaction of elemental carbon and gas blowing effect of H2 and CO2. The elemental carbon with different morphology and microstructure exhibits distinct electrochemical lithium storage performance including reversible capacity, rate capability, cycling stability, and Coulombic efficiency, owing to their different lithium storage mechanism. The elemental carbon synthesized at 30 bar CO2 delivers the highest reversible capacity of 506 mAh g−1 after 1000 cycles even at 1.0 A g−1. Advanced energy storage technology based on the green and low-carbon synthesis of carbon materials is a requisite for providing a stable and sustainable energy supply to meet the ever-growing demand for energy.
Laser directed energy deposition (LDED) offers great potential for fabricating dual nickel-based alloy blisks, due to its capability for in-suit alloying and creating graded powder-ratio zones to join dissimilar materials. However, blisk blades, which demand high-temperature durability, typically utilise γ'-strengthened nickel-based alloys, such as K477, which present challenges due to their poor weldability and high susceptibility to cracking. This study investigates the manufacturability of γ'-strengthened K477 for blisk blades and the mixtures of K477 and GH4169 for graded powder-ratio zones. The research focuses on the influence of laser power and powder ratios on microstructure, precipitated phases, elemental segregation, and crystal texture to elucidate the mechanisms of cracking. The results reveal that both solidification and liquation cracking contribute to crack formation, with liquation cracking being more pronounced at higher laser power. To address these challenges, an optimised laser power combined with a 0°/90° alternating rotation scanning strategy enables the successful deposition of high-density blocks (>99.8%) suitable for mechanical testing. These deposited blocks demonstrate exceptional mechanical properties at both 25°C and 870°C. This work provides a robust technical foundation for the reliable manufacturing of K477 and its transition zones with GH4169 in dual nickel-based alloy blisks using LDED.
COCOMO II is a constructive cost model that is widely used in the world.With function points or source lines of code and adjustment factors as input, it can predict software cost.Software process performance model is mainly used to indicate the relationship between the attributes and product in the software development process.Based on COCOMO II and process performance model theory, the viability that COCOMO II serves as a software process performance model is introduced in this paper.Controllable factors, the way to adjust them and benefits we can get are proposed.
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