Along with control of fire, iron smelting is one of the founding technological pillars of civilization. Industry has used the same basic process to make iron for over 3000 years. Yet, it is also one of the major global sources of greenhouse gas release. Iron, a basic commodity, is still produced by the greenhouse gas intensive reduction of iron oxide by carbon-coke and currently accounts for the release of one quarter of worldwide carbon dioxide emissions by industry. For instance, on average 1.9 tonnes of carbon dioxide are emitted for every tonne of steel produced. Due to a large share of coal in the energy mix of current production technology, the CO2 emissions are high. Through a new understanding of the chemistry of iron at high temperature, researchers have uncovered an effective new carbon-dioxide-free process to form iron.
Molding - a manufacturing technique that dates back to the Bronze Age - also has found applications in nanofabrication techniques in the production of high-density optical and magnetic storage media, organic light-emitting diodes, polymer photovoltaic cells, and field-effect transistors. The basic idea of molding is to shape a pliable raw material such as plastic, glass or metal into a desired form by filling it into the mold. Whether it is on the macro- or nanoscale, most molding methods are limited to replicate the patterns that are identical to the original master. To pattern different structures, new masters are needed for every different structure. Researchers have now developed an all-moldable nanofabrication platform that can generate, from a single master, nanoscale patterns with programmable densities, fill factors, and lattice symmetries. They have named this technique solvent-assisted nanoscale embossing (SANE).
A problem with conventional photolithography techniques is that they cannot achieve the small size requirement of nanoholes and nanopillars, required for various nanofabrication applications, because of the wavelength limitation of the exposure light source. Other nanolithography techniques, such as electron-beam lithography, focused ion beam milling, and x-ray lithography, have the high resolution to form these nanoholes and nanopillars. However, these techniques are all very expensive or have too low a throughput to fabricate a large area of repetitive nanopatterns. A low cost nanosphere lithography method for patterning and generation of semiconductor nanostructures provides a potential alternative to conventional top-down fabrication techniques.
Sophisticated molecular-size motors have evolved in nature, where they are used in virtually every important biological process. Some fascinating examples in nature are DNA and RNA polymerase, rotary motors such as ATP synthase, and flagella motors. In contrast, the development of synthetic nanomotors that mimic the function of these amazing natural systems and could be used in man-made nanodevices is in its infancy. Nevertheless, scientists are making good progress in achieving cargo transport by artificial nanomachines although often these advances are handicapped by several drawbacks. Researchers in Germany have now demonstrated the directed loading and transport of microobjects by high propulsion powered tubular microbots driven by a microbubble propulsion mechanism.
Biomechanical energy is one of the main energy components in biological systems. Developing an effective technique that can convert biomechanical energy into electricity is important for the future of in vivo implantable biosensors and other nanomedical devices. Researchers have already shown the conversion of biomechanical energy into electricity by a muscle-movement-driven nanogenerator to harvest mechanical energy from body movement under in vitro conditions. In a first demonstration of using nanotechnology to convert tiny physical motion into electricity in an in vivo environment, the same team has now reported the implanting of a nanogenerator in a live rat to harvest energy generated by its breath and heartbeat.
After achieving the 45-nm process, today's semiconductor industry is nearing the 20-nm process and looking for techniques that would enable sub-22-nm-half-pitch line patterns. Following the continuous increase in exposure tool numerical aperture, researchers are pursuing reductions in exposure wavelengths. This effort had them look at extreme ultraviolet (EUV: 13.4 nm in wavelength) as an exposure light source. Unlike the numerical aperture engineering, change of a light source to EUV demands development of its related components, such as photoresist and optics. Until a reliable solution for EUV lithography is developed, EUV interference lithography (EUVIL) would not solely advance the lithographic technology but would also help to optimize photoresist materials for EUV.
The manufacture of certain types of nanostructures - nanotubes, graphene, nanoparticles, etc. - has already entered industrial-scale mass production. However, the controlled fabrication of nanostructures with arbitrary shape and defined chemical composition is still a major challenge in nanotechnology applications. It appears that electron beams from electron microscopes (EM) - nowadays routinely focused down to the nanometer regime - are ideal candidates for versatile tools for nanotechnology. However, their usage is mostly restricted by the conditions in the corresponding electron microscopes, since most EMs are housed in high vacuum chambers the unintended electron-beam-induced deposition of residual gases is a problem, as well as the maintenance of well defined sample conditions. Researchers in Germany have now presented a novel way to use a highly focused electron beam to lithographically fabricate clean iron nanostructures. This new technique expands the application field for focused electron beams in nanotechnology.
Current fabrication technologies for nanoscale devices include deep-UV or electron-beam (e-beam) lithography. Both of these techniques involve successive deposition of metal or insulating layer and a resist layer, which is patterned using a UV source or a scanning electron beam. The process needs to be repeated for each layer of the architecture while the sample is taken out of the high vacuum chamber. Thus, multilayer lithography processes seriously compromise throughput and cost. In addition, the resolution is limited in the sub-10 nm regime. Researchers at the Institute of Bioengineering and Nanotechnology (IBN) in Singapore have now successfully demonstrated, for the first time, a lithography-free, direct-write technique for fabricating discrete field-effect transistors, as well as digital logic gates on a single nanowire.