Multiphoton lithography (MPL) is a microfabrication technique used to create three-dimensional microscale objects with complex geometrical arrangements. Of the various chemistries used to produce solid forms in MPL, protein photocrosslinking has been of particular value in biological applications. In new work, researchers have now described a strategy for creating a nearly unlimited range of microforms from crosslinked protein, including structures composed of multiple proteins. They also describe MPL microfabrication of complex unconstrained objects using high-viscosity protein-based reagents. To avoid drift during fabrication of microforms that are not in integral contact with a surface, the team developed a methodology for producing high-viscosity protein-based reagents, or "protogels". These materials allow the fabrication of protein-based objects that retain rotational and translational degrees of freedom.
Lithography based on block copolymer self-assembly has received significant attention due to the ability to achieve morphologies with dimensions in the range of 10 to 20 nm or even below. Block copolymer lithography is a cost-effective, parallel, and scalable nanolithography for densely packed periodic arrays of nanoscale features, whose typical dimension scale is beyond the resolution limit of conventional photolithography. Researchers have now introduced a conceptually new and versatile strategy to achieve asymmetric line patterns. This is the first work to demonstrate that highly asymmetric line nanopatterning is possible even though a block copolymer self-assembly technique is used.
Ultrasonic spray pyrolysis (USP) has been widely used in industry for spherical solid powder production, particularly of metal oxides. For some applications, though, porous particles are more desirable than dense ones. Back in 2005, researchers developed a technique to synthesize porous micro- and nanoparticles via USP. This method has since been expanded to prepare porous carbon microspheres. The high surface area and unique porous structures suggest that porous carbon spheres can be useful for electrode materials, adsorbents, and catalyst supports. Researchers at the University of Illinois already demonstrated the use of carbon microspheres as supercapacitors. Now, the team has expanded the aerosol synthesis of porous carbon materials by the use of energetic carbon precursors. Some of the resulting porous carbon spheres exhibit unique and unprecedented morphologies.
Buildings and other man-made structures consume as much as 30-40% of the primary energy in the world, mainly for heating, cooling, ventilation, and lighting. 'Smart' windows are expected to play a significant role in reducing the energy consumption of homes in two ways: by generating energy themselves; and by providing better insulation by allowing light in and keeping the heat out (in hot summers) or in (in cold winters). 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. In new work, researchers have now offered a simple method for promoting the production of monoclinic VO2 nanoparticles by doping.
Micro- and nanoporous materials can widely be found in nature, be it zeolite minerals, cell membranes, or diatom skeletons. Researchers are developing artificial analogues of such materials, i.e. nanoporous materials, for industrial applications in areas such as catalysis, water purification, environmental clean-up, molecular separation and proton exchange membranes for fuel cells. Manufacturing nanosieves with straight nanopores is still challenging, especially when the pore size is less than 10 nm. Researchers in Korea have now developed a novel material and fabrication technique that allows easy fabrication of nanosieves with sub-10 nm nanopores with straight pore-structure. With it, controlling the pore size from sub-nm to 5 nm becomes very easy.
Nanoporous alumina membranes are used in a wide range of applications, from photonics and sensors to bioelectronics or filtration membranes, since they are basically a 'universal' mold for making zero- or one-dimensional nanostructures of mostly any material or compound. With current fabrication processes, the main limitations of porous alumina templates are their pore size, which cannot be smaller than 25nm, and their polydomain structure, which prevents the possibility of addressing each nanopore individually for electronics applications. A new nanofabrication process by researchers from France and Germany allows to reduce the pore diameter while maintaining the self-ordering and keeping the lattice constant. This led to a new family of AAO templates with identical pores with a diameter below 10nm and a porosity of 3.5%.
Over the past few years, touchscreens have become ubiquitous in the world of mobile electronic devices. A next generation of touch sensing devices will be vastly more advanced and lead to ultrasensitive artificial skins. Another, novel model for advanced man-machine interactive systems could be based on moisture detectors. Here, actual touch is no longer necessary for a positioning interface to react; rather, the distribution of water molecules that exists around all humid surfaces, such as a human finger, would be sufficient to trigger a response. Researchers in China have now demonstrate such a flexible touchless positioning interface based on the spatial mapping of moisture distribution.
Many nanotechnology projects require some form of nanopatterning technique for fabricating the devices, structures and surfaces required in fields ranging from electronics to photonics, security, biotechnology and medicine. Although they may not be visible to the naked eye, the nanometer-sized trenches, ridges, curves and grooves of these patterns and surfaces have a very visible impact. Researchers have developed a wide range of nanopatterning techniques, from top-down methods such as nanoimprint, e-beam or UV lithography to bottom-up techniques such as transfer nanolithography or nanopositioning on DNA or protein scaffolds. A novel technique uses a biofunctionalization approach based on resist-less electron-beam-induced deposition of carbon-containing nanofeatures, that has been developed into a universal biofunctionalization platform. This unique ability can be exploited for biological experiments, where cells respond to the nanoscale density of activating molecules such as antibodies.