Mechanical Self-Assembly of a Strain-Engineered Flexible Layer: Wrinkling, Rolling, and Twisting

Self-shaping of curved structures, especially those involving flexible thin layers, has attracted increasing attention because of their broad potential applications in e.g. nanoelectromechanical/micro-electromechanical systems (NEMS/MEMS), sensors, artificial skins, stretchable electronics, robotics, and drug delivery. Here, we provide an overview of recent experimental, theoretical, and computational studies on the mechanical self-assembly of strain-engineered thin layers, with an emphasis on systems in which the competition between bending and stretchingenergy gives rise to a variety ofdeformations,such as wrinkling, rolling, and twisting. We address the principle of mechanical instabilities, which is often manifested in wrinkling or multistability of strain-engineered thin layers. The principles of shape selection and transition in helical ribbons are also systematically examined. We hope that a more comprehensive understanding of the mechanical principles underlying these rich phenomena can foster the development of new techniques for manufacturing functional three- dimensional structures on demand for a broad spectrum of engineering applications.Comment: 91 pages, 35 figures, review articl

The CUAVA-1 CubeSat—A Pathfinder Satellite for Remote Sensing and Earth Observation

In this paper we report a 3U CubeSat named CUAVA-1 designed by the ARC Training Centre for CubeSats, UAVs, and Their Applications (CUAVA). CUAVA, funded by the Australian Research Council, aims to train students, develop new instruments and technology to solve crucial problems, and help develop a world-class Australian industry in CubeSats, UAVs, and related products. The CUAVA-1 project is the Centre’s first CubeSat mission, following on from the 2 Australian satellites INSPIRE-2 and UNSW-EC0 CubeSats that launched in 2017. The mission is designed to serve as a precursor for a series of Earth observations missions and to demonstrate new technologies developed by our partners. We also intend to use the satellite to provide students hands-on experiences and to gain experience for our engineering, science and industry teams for future, more complex, missions

Atomic layer deposition of TiO2-nanomembrane-based photocatalysts with enhanced performance

In this study, TiO2 and TiO2-ZnO nanomembranes were fabricated by atomic layer deposition using the three-dimensionally porous template and their photocatalytic properties were investigated. The nanomembranes were firstly deposited onto the surface of polyurethane porous sponge templates (sacrificial templates), followed by a calcination at 500 or 800 °C. Three-dimensionally porous structures as a replica of the porous sponge templates were thus achieved. By a pulverizing process, the porous structures were broken into small pieces, which were then employed as photocatalyst. Experimental results show that the degree of crystallinity is raised by increasing of the nanomembrane thickness due to the increase of the grain size with minimizing the number of grain boundaries in the thicker nanomembrane, which is beneficial to enhance the photocatalysis efficiency. On the other hand, the photocatalytic activity can also be improved by TiO2-ZnO composite, due to lower electron-hole recombination possibility and better carrier conductivity

TiO2 Nanomembranes Fabricated by Atomic Layer Deposition for Supercapacitor Electrode with Enhanced Capacitance

Abstract TiO2 is a promising environment friendly, low cost, and high electrochemical performance material. However, impediments like high internal ion resistance and low electrical conductivity restrict its applications as electrode for supercapacitor. In the present work, atomic layer deposition was used to fabricate TiO2 nanomembranes (NMs) with accurately controlled thicknesses. The TiO2 NMs were then used as electrodes for high-performance pseudocapacitors. Experimental results demonstrated that the TiO2 NM with 100 ALD cycles had the highest capacitance of 2332 F/g at 1 A/g with energy density of 81 Wh/kg. The enhanced performance was ascribed to the large surface area and the interconnectivity in the case of ultra-thin and flexible NMs. Increased ALD cycles led to stiffer NMs and decreased capacitance. Moreover, one series of two supercapacitors can light up one light-emitting diode with a working voltage of ~ 1.5 V, sufficiently describing its application values

Cycling-Induced Capacity Increase of Graphene Aerogel/ZnO Nanomembrane Composite Anode Fabricated by Atomic Layer Deposition

Abstract Zinc oxide (ZnO) nanomembranes/graphene aerogel (GAZ) composites were successfully fabricated via atomic layer deposition (ALD). The composition of GAZ composites can be controlled by changing the number of ALD cycles. Experimental results demonstrated that the anode made from GAZ composite with ZnO nanomembrane of 100 ALD cycles exhibited highest specific capacity and best rate performance. A capacity increase of more than 2 times during the first 500 cycles was observed, and a highest capacity of 1200 mAh g−1 at current density of 1000 mA g−1 was observed after 500 cycles. On the basis of detailed electrochemical investigations, we ascribe the remarkable cycling-induced capacity increase to the alloying process accompanied by the formation of a polymer layer resulting from kinetically activated electrolyte degradation at low voltage regions

The growth mechanisms of TiO2 film onto PET surfaces by atomic layer deposition

Atomic layer deposition (ALD) was used to coat a polyethylene terephthalate (PET) polymer substrate with TiO _2 film. The TiO _2 was grown onto the surface with better film coverage by using thicker ALD deposition. Further evaluation on the coated substrates indicated that the reactive sites of –C=O that existed on PET surface played a significant contribution to facilitating the initial ALD growth of the TiO _2 thin film. The chemical composition of the coated substrates was characterised using energy dispersive X-ray spectroscopy, which showed that increasing the TiO _2 film thickness increased the Ti element content. Two growth mechanisms, namely, diffusion growth and direct coordination through the precursor coordination with surface reactive sites of –C=O with product release occurred simultaneously in the initial growth of TiO _2 coating onto PET polymer by ALD. The surface alteration of the coated ALD was characterised by Fourier transform infrared spectroscopy, which showed that the hydroxyl –OH groups emerged in the TiO _2 ALD film

"Sri Lankan Tamil Party Backs Opposition for President" by The Associated Press

"The Rajapaksa regime has been particularly harmful to the wellbeing of the Tamil-speaking peoples of Sri Lanka," the party said in a statement. It said the government had "failed to engage genuinely in a process of evolving an acceptable political solution, except to engage in deceitful and dilatory exercises." It said instead of resettling, rehabilitating and providing livelihood opportunities for hundreds of thousands of Tamil civilians displaced by the conflict, the government had resorte..