Vanadium dioxide (VO2) has long been recognized as a a material of significant technological interest for optics and electronics and a promising candidate for making 'smart' windows: it can transition from a transparent semiconductive state at low temperatures, allowing infrared radiation through, to an opaque metallic state at high temperatures, while still allowing visible light to get through. So far, VO2 hasn't been considered to be particularly suited for large-scale practical smart-window applications due to its low luminous transmittance and solar modulating ability. Researchers in China have now developed a process that can prepare VO2 thin-films with a controllable polymorph and morphology. Their results show that with increased porosity and decreased optical constants the performance of the VO2 films is enhanced, leading to a higher transmittance of visible light and improved solar modulating ability.
Block copolymer lithography is a cost-effective, parallel, and scalable nanolithography for the densely packed periodic arrays of nanoscale features, whose typical dimension scale is beyond the resolution limit of conventional photolithography. So far, it has been impossible to utilize block copolymer lithography on low surface energy materials such as Teflon, graphene or gold, where block copolymer thin film generally de-wets. To address this technological challenge, researchers in South Korea introduced block copolymer lithography that employs polydopamine coating - inspired by the adhesive proteins secreted by mussels - as a surface pretreatment for universal wettability generally applicable to arbitrary surfaces.
Currently, the primary tool for defining patterns at the micro- and nanometer scale is the mask aligner. Even where soft lithography methods are used, mask aligners are still often required to fabricate the masters. A mask aligner is a machine that is bulky in size and weight and is limited in the area that it can pattern in a single step. Also, a significant amount of infrastructure is needed for operation, such as high voltage power supplies and gas cooling lines. The average cost of this tool is in the six figures, which is a barrier for many labs and businesses in research and development of nanotechnologies. Researchers have now developed a compact and portable photolithography system based on a solid-state light source to remove these limiting factors and, at the same time, make available the high quality patterns that a mask aligner can produce.
Researchers have, for the first time, compared the energetic cost of silk and synthetic polymer fiber formation and demonstrated that, if we can learn how to spin like the spider, we should be able to cut the energy costs for polymer fiber processing by 90%, leaving alone the heat treatment requirements. The two routes of polymer fiber-spinning - one developed by nature and the other developed by man - show striking similarities: both start with liquid feed-stocks sharing comparable flow properties; in both cases the 'melts' are extruded through convergent dye designs; and for both 'spinning' results in highly ordered semicrystalline fibrous structures. In other words, analogous to the industrial melt spinning of a synthetic polymer, in the natural spinning of a silk the molecules (proteins) align (refold), nucleate (denature) and crystallize (aggregate).
Directed self-assembly of block copolymers is a candidate lithography for use in future nanoelectronics and patterned media copolymer with resolutions down to the sub-10nm domain. Variations of this effective nanofabrication technique have been used to write periodic arrays of nanoscale features into substrates at exceptionally high densities with resolutions that are difficult or impossible to achieve with top-down techniques alone. However, in many cases these approaches are either too costly or too complex due to the required number of processing steps, for instance expensive, time-consuming substrate pre-patterning. Researchers at the Molecular Foundry have now shown that block copolymers can be aligned on an unpatterned substrate using a removable and reusable mold applied from above.
There is a lot of buzz in the computer industry about so-called three-dimensional (3D) chips, promising higher performance with lower energy consumption, and paving the way for exascale computers (which would represent a thousandfold increase in performance over the current petascale architecture). However, these chips are not intrinsically built, true 3D chips; rather, they are stacked layers of up to 100 separate chips. In a major breakthrough in the field of photonic crystals, researchers in The Netherlands have developed a novel process that allows for rapid fabrication of large 3D photonic crystals in mono-crystalline silicon using CMOS compatible processes.
Conventional microfluidic devices are fabricated in inherently planar, block-like devices. In contrast, an important feature of naturally self-assembled systems such as leaves and tissues is that they are curved and have embedded fluidic channels that enable the transport of nutrients to, or removal of waste from, specific three-dimensional regions. Since most microfluidic devices are created using layer-by-layer lithographic patterning and molding methods, it is challenging to create microfluidic networks in curved or folded geometries. However, such networks are important to pattern chemicals in 3D and also to create realistic models of tissues. Researchers have now demonstrated, for the first time, a strategy to self-assemble curved and folded microfluidic polymeric devices with materials used in conventional planar, microfluidics namely SU8 and PDMS.
Cost of ownership has become a critical challenge facing future research in nanofabrication. As potential applications have broadened beyond the high-volume manufacture of integrated circuits, demand has increased for a robust tool capable of lithography at high pattern density and fidelity but also at low cost and thus suitable for scientific research, rapid prototyping, and low-volume manufacturing. Unfortunately, current manufacturing technologies employed in the chip industry are anything but 'low cost'. Researchers have now demonstrated a new source for lithography that has both higher per-particle exposure efficiency and a higher brightness than the sources conventionally used for lithography at the 10 nm scale.