Morphable 3D mesostructures and microelectronic devices by multistable buckling mechanics.

Three-dimensional (3D) structures capable of reversible transformations in their geometrical layouts have important applications across a broad range of areas. Most morphable 3D systems rely on concepts inspired by origami/kirigami or techniques of 3D printing with responsive materials. The development of schemes that can simultaneously apply across a wide range of size scales and with classes of advanced materials found in state-of-the-art microsystem technologies remains challenging. Here, we introduce a set of concepts for morphable 3D mesostructures in diverse materials and fully formed planar devices spanning length scales from micrometres to millimetres. The approaches rely on elastomer platforms deformed in different time sequences to elastically alter the 3D geometries of supported mesostructures via nonlinear mechanical buckling. Over 20 examples have been experimentally and theoretically investigated, including mesostructures that can be reshaped between different geometries as well as those that can morph into three or more distinct states. An adaptive radiofrequency circuit and a concealable electromagnetic device provide examples of functionally reconfigurable microelectronic devices.

Positive correlation between PSI response and oxidative pentose phosphate pathway activity during salt stress in an intertidal macroalga.

Studies have demonstrated that photosynthetic limitations and starch degradation are responses to stress; however, the relationship between the two is seldom described in detail. In this article, the effects of salt stress on photosynthesis, the levels of NADPH and total RNA, the starch content and the activities of glucose-6-phosphate dehydrogenase (G6PDH) and ribulose-5-phosphate kinase (RPK) were evaluated. In thalli that underwent salt treatments, the cyclic electron flow through PSI showed greater stress tolerance than the flow through PSII. Even though the linear electron flow was suppressed by DCMU, the cyclic electron flow still operated. The electron transport rate I (ETRI) increased as the salinity increased when the thalli recovered in seawater containing DCMU. These results suggested that PSI receives electrons from a source other than PSII. Furthermore, the starch content and RPK activity decreased, while the content of NADPH and total RNA, and the activity of G6PDH increased under salt stress. Soluble sugar from starch degradation may enter the oxidative pentose phosphate pathway (OPPP) to produce NADPH and ribose 5-phosphate. Data analysis suggests that NADPH provides electrons for PSI in Ulva prolifera during salt stress, the OPPP participates in the stress response and total RNA is synthesized in excess to assist recovery.

3D hierarchical architectures based on self-rolled-up silicon nitride membranes.

This study presents the superior structural versatility of strained silicon nitride (SiNx) membranes as a platform for three-dimensional (3D) hierarchical tubular architectures. The effects of compressive and tensile stressed SiNx layer thickness on the self-rolled-up tube curvature, the sacrificial layer etching anisotropy on rolling direction and chirality, and stress engineering by localized thickness control or thermal treatment, are explored systematically. Using strained SiNx membranes as an electrically insulating and optically transparent mechanical support, compact 3D hierarchical architectures involving carbon nanotube arrays and passive electronic components are demonstrated by releasing the functional structures deposited and patterned in 2D. These examples highlight the uniqueness of this platform that exploits 2D processing and self-assembly to achieve highly functional 3D structures.

Modifying the Power and Performance of 2-Dimensional MoS2 Field Effect Transistors.

Over the past 60 years, the semiconductor industry has been the core driver for the development of information technology, contributing to the birth of integrated circuits, Internet, artificial intelligence, and Internet of Things. Semiconductor technology has been evolving in structure and material with co-optimization of performance-power-area-cost until the state-of-the-art sub-5-nm node. Two-dimensional (2D) semiconductors are recognized by the industry and academia as a hopeful solution to break through the quantum confinement for the future technology nodes. In the recent 10 years, the key issues on 2D semiconductors regarding material, processing, and integration have been overcome in sequence, making 2D semiconductors already on the verge of application. In this paper, the evolution of transistors is reviewed by outlining the potential of 2D semiconductors as a technological option beyond the scaled metal oxide semiconductor field-effect transistors. We mainly focus on the optimization strategies of mobility (µ), equivalent oxide thickness (EOT), and contact resistance (RC ), which enables high ON current (Ion ) with reduced driving voltage (Vdd ). Finally, we prospect the semiconductor technology roadmap by summarizing the technological development of 2D semiconductors over the past decade.

Quantitative Evaluation of Plant and Modern Urban Landscape Spatial Scale Based on Multiscale Convolutional Neural Network.

Modern urban landscape is a simple ecosystem, which is of great significance to the sustainable development of the city. This study proposes a landscape information extraction model based on deep convolutional neural network, studies the multiscale landscape convolutional neural network classification method, constructs a landscape information extraction model based on multiscale CNN, and finally analyzes the quantitative effect of deep convolutional neural network. The results show that the overall kappa coefficient is 0.91 and the classification accuracy is 93% by calculating the confusion matrix, production accuracy, and user accuracy. The method proposed in this study can identify more than 90% of water targets, the user accuracy and production accuracy are 99.78% and 91.94%, respectively, and the overall accuracy is 93.33%. The method proposed in this study is obviously better than other methods, and the kappa coefficient and overall accuracy are the best. This study provides a certain reference value for the quantitative evaluation of modern urban landscape spatial scale.

The threshold effect of cost-based environmental regulation on thermal power generation environmental governance efficiency.

A network data envelopment analysis slack-based measure (NSBM) was applied to explore the thermal power generation environmental governance efficiency (TGGE) of 30 provinces in China except Tibet from 2006 to 2015, and then the threshold panel data model was established to study the nonlinear impact of cost-based environmental regulation (CER) on TGGE. The results show that (1) thermal power generation efficiency (TGE) is relatively low but shows a fluctuation growth trend, and TGGE is lower than thermal power generation production efficiency (TGPE); (2) CER has a significant single-threshold effect on the TGGE in China. When the proportion of CER to gross domestic production (GDP) is less than 3.023, the regulation has a significant positive effect on TGGE, while when the proportion of CER to GDP is larger than 3.023, the positive effect is greatly reduced from 0.073 to 0.002. The same conclusion can be obtained using the ratio of CER to gross industrial output value as the threshold variable, although with a different threshold value. From the average value of the sample period, for the vast majority of provinces, the effects of CER on TGGE are not significant. Based on these, relevant policy implications are presented to further promote TGGE.

Ultra-Small, High-Frequency, and Substrate-Immune Microtube Inductors Transformed from 2D to 3D.

Monolithic on-chip inductors are key passive devices in radio frequency integrated circuits (RFICs). Currently, 70-80% of the on-wafer area of most RFIC chips is occupied by the sprawling planar spiral inductors, and its operation frequency is limited to a few GHz. With continuous scaling of the transistor technology, miniaturization and high frequency operation of inductors have become the bottleneck to meet future demands of wireless communication systems. Here we report on-chip self-rolled-up 3D microtube inductors with extremely small footprint, unprecedented high frequency performance and weak dependence on substrate conductivity. The serpentine metal strips are deposited on an oppositely strained silicon nitrides (SiNx) bilayer. After releasing from the sacrificial layer underneath, the metal/SiNx layer is scrolled into a 3D hollow tubular structure by the strain induced unidirectional self-rolled-up technology. Compared to the planar spiral inductors with similar inductances and quality (Q) factors, the footprint of tube inductors is reduced by as much as two orders of magnitude, and the frequency at peak Q factor improves more than 5 times on doped substrates. The self-rolled-up 3D nanotechnology platform employed here, that "processes in 2D but functions in 3D", is positioned to serve as a global solution for extreme RFIC miniaturization with improved performance.