Neno teconoligy & Science

                                                           Nanotechnology

• Nanotechnology is science and engineering at the scale of atoms and molecules. Get the basics on this amazing new technology in our beginner's guide,

In its original sense, 'nanotechnology' refers to the projected ability to construct items from the bottom up, using techniques and tools being developed today to make complete, high performance products.

• When K. Eric Drexler (right) popularized the word 'nanotechnology' in the 1980's, he was talking about building machines on the scale of molecules, a few nanometers wide—motors, robot arms, and even whole computers, far smaller than a cell.

•  Drexler spent the next ten years describing and analyzing these incredible devices, and responding to accusations of science fiction. Meanwhile, mundane technology was developing the ability to build simple structures on a molecular scale. As nanotechnology became an accepted concept, the meaning of the word shifted to encompass the simpler kinds of nanometer-scale technology. 

• The U.S. National Nanotechnology Initiative was created to fund this kind of nanotech: their definition includes anything smaller than 100 nanometers with novel properties.

• Much of the work being done today that carries the name 'nanotechnology' is not nanotechnology in the original meaning of the word. Nanotechnology, in its traditional sense, means building things from the bottom up, with atomic precision. This theoretical capability was envisioned as early as 1959 by the renowned physicist Richard Feynman.

I want to build a billion tiny factories, models of each other, which are manufacturing simultaneously. . . The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big.

                                                                                       — Richard Feynman, Nobel Prize winner in physics

• Based on Feynman's vision of miniature factories using nanomachines to build complex products, advanced nanotechnology (sometimes referred to as

molecular manufacturing will make use of positionally-controlled mechanochemistry guided by molecular machine systems.

• Formulating a roadmap for development of this kind of nanotechnology is now an objective of a broadly based technology roadmap project led by Battelle (the manager of several U.S. National Laboratories) and the Foresight Nanotech Institute.

• Shortly after this envisioned molecular machinery is created, it will result in a manufacturing revolution, probably causing severe disruption. It also has serious economic, social, environmental, and military implications.

• Nanotechnology (sometimes shortened to "nanotech") is the manipulation of matter on an atomic and molecular scale. Generally, nanotechnology works with materials, devices, and other structures with at least one dimension sized from 1 to 100 nanometres. Quantum mechanical effects are important at this quantum-realm scale.

•  With a variety of potential applications, nanotechnology is a key technology for the future and governments have invested billions of dollars in its research. Through its National Nanotechnology Initiative, the USA has invested 3.7 billion dollars. The European Union has invested 1.2 billion and Japan 750 million dollars.

• Nanotechnology is very diverse, ranging from extensions of conventional device physics to completely new approaches based upon molecular self-assembly, from developing new materials with dimensions on the nanoscale to direct control of matter on the atomic scale. Nanotechnology entails the application of fields of science as diverse as surface science, organic chemistry, molecular biology, semiconductor physics, microfabrication, etc.

• Scientists currently debate the future implications of nanotechnology. Nanotechnology may be able to create many new materials and devices with a vast range of applications, such as in medicine, electronics, biomaterials and energy production. On the other hand, nanotechnology raises many of the same issues as any new technology, including concerns about the toxicity and environmental impact of nanomaterials, and their potential effects on global economics, as well as speculation about various doomsday scenarios. These concerns have led to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.

                                            
                                                Superlattices

• Protein cages can be used to guide the assembly of binary nanoparticle superlattices through tunable electrostatic interactions with charged gold nanoparticles.

                                         Memristive devices

• This Review looks at recent progress in the development and understanding of memristive devices, and examines the performance requirements for computing with such devices.

                                               Graphene

• Scanning tunnelling microscopy and X-ray photoemission spectroscopy measurements reveal that yttria, a high-κ dielectric, can form a complete monolayer on platinum-supported graphene.

                                         Organic electronics

• Weak van der Waals interactions control the packing of self-assembled monolayers in a molecular diode and have a remarkable effect on the device performance.

                                    Graphene heterostructures

• A tunnelling transistor based on stacks of chemically grown graphene and other two-dimensional layers shows record performance.

                                           Molecular motors

• A molecular motor adsorbed on a gold surface can be made to rotate in a clockwise or anticlockwise direction by selective inelastic electron tunnelling through different subunits of the motor.

                                         
                                           Superconductivity

• Experiments on an YBa₂Cu₃O_7–δ nano-island reveal fundamental information about the order parameter in this type of high-temperature superconducting material.

                                               Nanomaterials

• The metal detoxification pathway in the earthworm can be exploited for the synthesis of luminescent semiconductor quantum dots that could be used in live cell imaging.

        Environmental Regulator Launches New Effort to  Monitor Hormonelike Chemicals

• The U.S. Environmental Protection Agency, responding to scientists' concerns, will now study whether low doses of hormonelike chemicals cause human harm.

 

• Handling water bottles is one way people are exposed to the endocrine disruptor BPA. Image: Flickr/Klearchos Kapoutsis.

• Spurred by mounting scientific evidence, the U.S. Environmental Protection Agency is initiating a new effort to examine whether low doses of hormone-mimicking chemicals are harming human health and whether chemical testing should be overhauled.

• The EPA, responding to a report by a group of 12 scientists published in March, is collaborating with other federal agencies to assess whether the traces of chemicals found in food, cosmetics, pesticides and plastics affect human development and reproduction. As part of that review, they will evaluate whether current testing is capturing effects linked to hormone mimics, and if the agency should alter its risk assessments.

• The federal officials will complete a “state of the science” paper by the end of 2013, which then reportedly will be reviewed by a national panel of scientists.

• “The state of the science paper findings will provide information to help inform how the safety of chemicals [is] assessed,” according to the EPA website.

• “While EPA is interested in all aspects of low dose extrapolation, this short term effort is designed to meet immediate science-policy needs.”

• There is longstanding disagreement in the scientific community whether exposure to substances that mimic or block estrogen, testosterone and other hormones leads to human health impacts.

• However, a report released in March concluded that small doses can have big effects. For three years, researchers led by Tufts University’s Laura Vandenberg examined hundreds of studies on the effects of endocrine-disrupting chemicals and their report found that the evidence “clearly indicates that low doses cannot be ignored.”

• The scientists in that report criticized the federal government’s decades-old strategy for testing most chemicals – exposing lab rodents to high doses then extrapolating down for real-life human exposures. They said it is inadequate to protect people and urged reforms because hormone-like chemicals can have health effects at low doses that do not occur at high doses.

• The EPA, in its new effort, will evaluate this phenomenon, which is called "non-monotonic dose response."

• “Current testing paradigms are missing important, sensitive endpoints” for human health, the scientists said in their report, published in the journal Endocrine Reviews. “The effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health.”

• Pete Myers, founder of Environmental Health News and chief scientist at Environmental Health Sciences, was the senior author of the report.

• University of Missouri professor Frederick vom Saal, a co-author of the report, said it is about time the government takes low doses seriously.

• “I’m thrilled they’re doing this and it’s desperately needed,” said vom Saal, who studies effects of low doses of bisphenol A (BPA) in rodents. “Hopefully it won’t take long and we can stop asking whether there are low-dose effects and then deal with the fact that there are.”

• Vom Saal said the EPA and U.S. Food and Drug Administration (FDA) currently makes “very frightening assumptions” about exposures to these chemicals, such as BPA, which is found in canned food liners, polycarbonate plastic and some paper receipts.

• “You cannot test a hormone like you would a toxicant,” he said. “A chemical that adds or subtracts to hormones already in your body is going to have effects at low levels.”

• Vom Saal said federal agencies have for years determined the safety of endocrine-disrupting compounds without testing them at low levels. “There are no such thing as safe levels when you’re talking endocrine disruptors,” he said.

                    Graphene Towers Promise "Flexi-Electronics"

• 3-D graphene blocks—grown between forming ice crystals—add elasticity to the super strength and conductivity of sheets of graphene, a 2-D form of carbon first isolated less than a decade ago.

 

• The graphene towers' honeycomb structure gives it super strength and resilience. Image: L. Qiu, Monash University .

• It can support 50,000 times its own weight, springs back into shape after being compressed by up to 80% and has a density much lower than most comparable metal-based materials. A new superelastic, three-dimensional form of graphene can even conduct electricity, paving the way for flexible electronics, researchers say.

• The team, led by Dan Li, a materials engineer at Monash University in Clayton, Australia, coaxed 1-centimeter-high graphene blocks or 'monoliths' from tiny flakes of graphene oxide, using ice crystals as templates. The work is published today in Nature Communications.

• Graphene, a two-dimensional form of carbon that was first isolated less than a decade ago, has exceptional mechanical strength and electrical conductivity, but making use of these properties means first finding ways to scale up from nano-sized flakes (see ‘Graphene spun into metre-long fibers’).

• Li and his colleagues adapted an industrial technique called freeze casting to do just that. This involves growing layers of an oxygen-coated, soluble version of graphene called graphene oxide between forming ice crystals. On cooling the aqueous solution of graphene oxide flakes, a thin layer of the nanomaterial becomes trapped between the growing crystals, forming a continuous network that retains its structure once the ice is thawed.

• Researchers have used this method before, but the resulting material had poor mechanical strength — a property that Li attributes to the oxygen layer that coats each flake, which weakens bonding between neighboring flakes in the network.        

• In the latest study, researchers show that by partially stripping the oxygen coating before freeze casting, they could enhance the bonding between adjacent flakes in the network, producing much stronger materials.

• After freeze casting, the honeycomb-like network held its shape as the ice was removed. The researchers could then chemically convert the graphene oxide into graphene, strengthening inter-sheet bonding, and so the material itself, still further.

                                         
                                          Fill the void

Li attributes the new graphene's properties to its structure: the individual graphene sheets are neatly aligned, forming an ordered network of hexagonal pores.

• Rodney Ruoff, a researcher in graphene assemblies at the University of Texas at Austin, says that the material “is very interesting for the extremely low density that the researchers achieve, as well as its exceptional mechanics”. He adds that the structure could be used as a scaffold for flexible battery electrodes, or form the basis of many composite materials. “It would be interesting to fill the pores with rubber materials, for example,” he says. “There is a great interest in making rubber thermally or electrically conductive without harming its elastic properties.”

• Li says that the superelastic graphene has potential for use in biomedical applications. “Biomaterials people are very interested in this structure because the pore sizes match existing tissue scaffolds very well,” he says.

Self-Healing, Stretchable Wires Created Using Liquid Metal

• Researchers from North Carolina State University have developed elastic, self-healing wires in which both the liquid-metal core and the polymer sheath reconnect at the molecular level after being severed.

"Because we're using liquid metal, these wires have excellent conductive properties," says Dr. Michael Dickey, an assistant professor of chemical and biomolecular engineering at NC State and co-author of a paper on the work. "And because the wires are also elastic and self-healing, they have a lot of potential for use in technologies that could be exposed to high-stress environments."

• The researchers first created tiny tunnels, called microfluidic channels, in a commercially available self-healing polymer using solid wire. By filling those channels with a liquid-metal alloy of indium and gallium, they were able to create a liquid-metal wire in an elastic sheath. Because the wire is liquid, it can be stretched along with the polymer sheath.

• When the wires are sliced or severed, the liquid metal oxidizes -- forming a "skin" that prevents it from leaking out of its sheath. When the severed edges of the wire are placed back together, the liquid metal reconnects and the sheath re-forms its molecular bonds.

• "We're also excited about this work because it allows us to create more complex circuits and rewire existing circuits using nothing more than a pair of scissors by cutting and reconfiguring the wires so that they connect in different ways," Dickey says.

• Similarly, the technique developed by Dickey's team could be used to create complex, three-dimensional structures with connecting microfluidic channels, by cutting the polymer sheath into sections and reconnecting them at different angles with the channels still in alignment.