In the past, random defects caused by particle contamination were the dominant reason for yield loss in the semiconductor industry - defects occur in the patterning process (so-called process defects) when contaminants become lodged in or on the wafer surface. Trying to prevent such fabrication defects, chip manufacturers have spent much effort and money to improve the fabrication process, for instance by installing ultra-clean fabrication facilities. With the semiconductor industry's move to advanced nanometer nodes, and feature sizes approaches the limitation of the fabrication method used, particles are no longer the only problem for chip manufacturers. In a nanoscale feature-size fabrication environment, systematic variations, such as metal width and thickness variations or mask misalignment, are also major contributors to yield loss. Rather than perfecting a nanostructure by improving its original fabrication method, researchers at Princeton University have demonstrated a new method, known as self-perfection by liquefaction (SPEL), which removes nanostructure fabrication defects and improves nanostructures after fabrication.
Sophisticated molecular-size motors have evolved in nature, where they are used in virtually every important biological process. 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. Building nanoscale motors is not just an exercise in scaling down the design of a macroworld engine to nanoscale dimensions. Many factors such as friction, heat dissipation and many other mechanical behaviors are just very different at this scale - everything is constantly moving (under kinetic energy supplied by the heat of the surroundings) and being buffeted by other atoms and molecules (Brownian motion). In nature, biological motors use catalytic reactions to create forces based on chemical changes. These motors do not require external energy sources such as electric or magnetic fields. Instead, the input energy is supplied locally and chemically. Despite impressive progress over the past years, man-made nanomachines lack the efficiency and speed of their biological counterparts. New research has demonstrated that the incorporation of carbon nanotubes (CNT) into the platinum component of asymmetric metal nanowire motors leads to dramatically accelerated movement in hydrogen peroxide solutions, with average speeds of 50-60 micrometers per second.
It wasn't market forces that landed a man on the moon; and It wasn't market forces that led France to build a nuclear energy infrastructure that now enables it to generate some 75% of its entire energy needs from nuclear power (just an example of what energy policy can do; let's not get into a discussion here of nuclear energy, though). But somehow, the leading political and industrial forces in the United States - together with China the largest emitter of greenhouse gases on the planet - think that a task so fundamental and massive as fighting global warming and environmental pollution should mostly be left 'to the market'. Unfortunately, it's just a matter of economic reality that 'the market' will not invest in new energy technologies on a large scale until existing ways of producing energy become more expensive than producing alternative energies - which at the moment they aren't. As is the case with almost all emerging technologies, government initially lends a helping hand before the technology becomes a viable commercial proposition and the market takes over (remember how the Internet got created?). In the case of future clean energy technologies, it appears that this 'helping hand' needs to be massive and swift. It's not so much that clean/green tech wouldn't develop over time on its own. But it's against the backdrop of accelerating global warming that it becomes a top priority that requires massive public resources.
The race is on to develop the next generation of nanotechnology-enabled electrochemical energy storage devices, also knows as batteries. Lithium of course has long been recognized as an ideal material for energy storage due to its light weight and high electrochemical energy potential, as witnessed by the ubiquitous use of Li-ion batteries. There still seems to be considerable potential to further improve the performance characteristics of these Li-ion batteries. There have been many design approaches to creating lithium ion batteries but they usually share common features: The positive electrode is typically a lithium metal oxide, with various metals used such as cobalt, nickel, and manganese. The negative electrode is typically a carbon compound or natural or synthetic graphite. Researchers in Germany have now demonstrated a simple route for transforming cheap commercial carbon nanotubes into highly efficient carbon for electrochemical energy storage applications. When tested as electrode materials for lithium batteries, this composite material exhibits excellent performance over long test cycles.
In case you haven't seen the absolutely amazing animation 'Cellular Visions: The Inner Life of a Cell' yet, go watch it now. In it, there is a sequence where a motor protein is sort of 'walking' along a filament, dragging this round sphere of lipids behind it. This kind of nanoscale biological motor is able to load/unload particular types of cargo without external stimuli, and transport them along cytoskeletal filaments by using the energy of adenosine triphosphate (ATP) hydrolysis within cells. Nanotechnology researchers are fascinated by the various molecular delivery systems that have evolved in nature and they are receiving increasing attention as blueprints for nanoscale actuators and building blocks to construct artificially-engineered bio-hybrid systems. Some researchers expect that artificial molecular transport systems which utilize microtubules motility will be an alternative way to pressure-driven or electrokinetic flow-based microfluidic devices. Researchers in Japan propose a molecular transport system that can achieve autonomous loading/unloading of specified cargoes. This system loads a cargo molecule through DNA hybridization.
Future nanomanufacturing processes will rely on two basic principles: a combination of chemical synthesis and self-assembly on one hand and robotic nanofabrication on the other. While the former is a controlled 'natural' process relying on chemistry and self-organization principles of nature, the latter will be an industrial process similar in concept to today's automated manufacturing assembly lines. Robotic assembly lines in modern factories have come a long way since the early 20th century when Henry Ford first used an assembly line on an industrial scale for his Model T automobile. Nevertheless, the principle is the same. Rather than having a single craftsman or team of craftsmen create each part of a product individually and assemble them together into a single item, an assembly line is a (often completely automated) manufacturing process in which interchangeable parts are added to a product in a sequential manner to create a finished product. While sporadic automation of certain tasks has already begun (for instance, automated microrobotic injection of foreign materials into biological cells), nanotechnology techniques today are pretty much where the industrial world was before Ford's assembly line - a domain of highly skilled artisans and not of automated mass production. It has long been a dream for nanotechnologists that robots could one day be used in an assembly line type of process to manufacture nanodevices. Researchers are beginning to develop the first rudimentary nanomanipulation devices that could lead to future automated manufacturing systems. Now, a team of scientists in Canada have reported the first demonstration of closed-loop force-controlled grasping at the nanonewton level.
Following up on yesterday's Spotlight about graphene quantum dots, today we look at what might be the first realistic application of this revolutionary material. Back in December we reported on the development of transparent and conductive graphene-based composites for use as window electrodes in solid-state dye sensitized solar cells. While the researchers who conducted this work produced graphene by chemical oxidation of graphite, a multi-step process, new results from the University of Manchester group that discovered graphene in 2004 show a simpler route to producing graphene films that cannot only be used for solar cells but might be well suited for liquid crystal displays.
We have written about scientists' fascination with graphene - the flat one-atom thick sheet of carbon - before. Over the past couple of years, graphene has become a new model system for condensed-matter physics - the branch of physics that deals with the physical properties of solid materials - because it enables table-top experimental tests of quantum relativistic phenomena, some of which are unobservable in high-energy physics. The behavior of electrons in graphene is very different from their behavior in typical semiconductors. In the latter, they possess a mass, and a finite energy (called the energy gap) is necessary to move the electrons from the valence to the conductance band and they move like regular particles, increasing their speed as they get accelerated. In graphene, electrons move with a constant speed - much faster than electrons in other semiconductors - independent of their kinetic energy (similar to the behavior of photons), and there is no energy gap. Graphene, which basically is an unrolled, planar form of a carbon nanotube therefore has become an extremely interesting candidate material for nanoscale electronics. Researchers in the UK have now, for the first time, shown that it is possible to carve out nanoscale transistors from a single graphene crystal.