May 27, 2006

Advancing the automation and chemistry of scanning tunneling microscopes: autonomous atom assembler

This is movement towards the transition stage of molecular nanotechnology. If the goals described here are achieved (automated three dimensional pick and place of atoms) and that is then sped up and made massively parallel that level of technology would be the level of transition stage molecular manufacturing. The article is from late 2003. The researcher Bob Cellota is now the director of the NIST center for nanoscale science and technology

Researchers are advancing the automation and chemistry of scanning tunneling microscopes

Current work and progress:
-Moving the atom tip even closer so that the atom on the tip and the atom on the surface can form a temporary, sort of tunable, temporary chemical bond and then using the forces of that chemical bond, we move atoms around on the surface. Now that's been done before, by hand to make very beautiful structures on the surface. And what we're in the middle of is teaching a computer how to do this. So this can autonomously assemble whatever structures we want starting from a random collection of atoms. We just feed it a drawing of what we'd like and it figures out how to move the atoms and in what order and at what speeds and in which ways to create the structures we want. And we call this an autonomous atom assembler. Celotta's autonomous atom assembler does it's work in a high vacuum, at low temperatures.
-It's just beginning to work and we're making simple structures on the surface of circles, triangles and squares and once we learn the kind of rules it needs to have in order to make these structures -- let me give you an example of a rule -- if you're going to move an atom past another atom, you don't want to get too close because there'll be a chemical attraction between the two and they'll form a dimer -- a two atom pair. So you have to give it a certain wide berth when you put them together and we also have to make the quickest routes possible and we have to worry about other defects in the surface. So we're teaching it a whole bunch of rules to follow and then trying to see how well we can construct a surface where it just does all the thinking. And of course, when you try to teach a computer to do something, you have to know all the rules. So it forces it to understand all the kinds of interaction that can happen on the surface and be able to convey that to the computer so it can work correctly.

Looking at the next steps to advancing scanning tunneling microscopes.
-Have different kinds of atoms and keep them straight, so that you can assemble things out of multiple species of atoms on the surface.
-Do things in three dimensions to bring atoms up so you assemble a small cluster of atoms, say a square that was all filled in on one layer and then build something on top of that square.
-Another major step would be to actually understand the interaction between the atom on the tip and the atom on the surface -- that is actually understand the forces ... and it's really chemistry on a very fine level
-Reliably figure out how to pick an atom up on the surface and put it on the end of the tip and then also reliably put it back exactly onto the surface where you want it. It's kind of like a crane on a construction site. So we're actually now moving the atoms around more like bulldozers where we're pushing them around on the surface or dragging them around on the surface might be more correct. A future enhancement might be to pick each one up selectively and put it down.

May 26, 2006

Artificial islands

other tech: Japanese make Robot hand controlled by thought alone

The robotic hand mimics the movements of a person's real hand, based on real-time functional magnetic resonance imaging (fMRI) of their brain activity. It marks another landmark in the advance towards prosthetics and computers that can be operating by thought alone. An fMRI machine probes activity within the brain by monitoring blood flow to different regions. It uses a powerful magnetic field combined with radiofrequency pulses to probe the magnetic state of hydrogen atoms in water molecules within body tissue.

An alternative and more portable method is to measure electrical activity inside the brain using electrodes either implanted in brain tissue or attached to the scalp. US researchers have previously used brain implants to allow monkeys to remotely operate robotic arms.

One day, Kamitani believes, the robot hand could be made to respond faster than a user's real one. "The next step for me is to decode faster, even before the person moves their hand, by reading the brain activity related to intention," he told New Scientist.

But he admits that fMRI scanning technology must be improved dramatically before this could be possible, and before the system could be used practically. "We will need several breakthroughs in related technologies, including those for brain scanning hardware, before this type of non-invasive systems will be used in daily life," he says.

For now, the fMRI technique is too cumbersome and expensive but could help scientists better understand how the brain works because it provides higher resolution.

Carbon Nanotube Computers: complex circuits arranged

IBM researchers have made an important breakthrough: arranging nanotube transistors for complex circuits. Researchers at IBM have overcome an important obstacle to building computers based on carbon nanotubes, by developing a way to selectively arrange transistors that were made using the carbon molecules. The achievement, described in the current issue of Nano Letters, could help make large-scale integrated circuits built out of carbon nanotubes possible, leading to ultrafast, low-power processors. According to estimates, carbon nanotubes have the potential to produce transistors that run 10 times faster than even anticipated future generations of silicon-based devices, while at the same time using less power. To gain control over the arrangement of transistors, the IBM researchers coated the nanotubes with molecules that bind only to patterns of metal oxide lines on a surface, and not to the areas in-between.

To make working transistors, the researchers laid down lines of aluminum using a lithography technique. These wires serve as the gates that turn the transistors on and off. They then oxidized the aluminum to form a thin aluminum oxide layer on top of the wires, which acts as both a dielectric and the material to which the nanotubes will bind. After applying carbon nanotubes in solution and allowing them to bind to the aluminum oxide, the researchers deposited palladium leads perpendicular to the aluminum/aluminum oxide wires. These leads crossed over the nanotubes, becoming the source and drain of the transistor.

While developing this method of organizing nanotube transistors is an important step, much work remains to be done before commercial processors will be available. For one thing, exploiting the full potential of nanotube transistors will require improving the leads, possibly by using nanotubes in place of the palladium wires.

But perhaps a more pressing problem is finding reliable and inexpensive ways to isolate different types of carbon nanotubes. Current fabrication techniques produce a mix of nanotubes with different sizes and electronic properties, not all of which will work well in integrated circuits.

Because of these challenges, the first applications of carbon nanotube transistors will probably not be as high-performance processors, Hannon says, but highly sensitive sensors that work even with a mix of different nanotubes.

Invisibility part II

Anyone making such a cloak would have to choose what form of radiation one wanted invisibility from. The invisibility would work both ways--a person hidden from the visible light spectrum would have to use infrared or sonar or microwaves to see out. Note: I believe they could leave a pinhole in the visible spectrum which would be difficult to spot that someone inside could use to look out.

More technical details at the MIT technology review The cloaking effect depends on a material's "refractive index," or its ability to influence the direction of light that passes through it. Light tends to prefer the quickest route between two points, which is normally a straight line. With metamaterials, however, the quickest path can be one that bends around an object.

But bending light is just one of the requirements for cloaking. "You have to return the light to the same path it was pursuing before it hit the cloak; otherwise it casts a shadow," says Pendry. Similarly, when light enters the cloak, it must not be reflected. "One way to think about it is that this material gives the appearance of being like space," says Smith, in that space can bend light and also has no reflection.

"It's a breakthrough," says George Eleftheriades, an expert in metamaterials at the University of Toronto. However, he says, there is a limitation: "It won't work for every frequency."

Indeed current materials are capable of redirecting only microwaves, which means the cloaking device Smith and Schurig are developing will work only against radar or other microwave emitters. While this is likely to prove useful for future stealth planes, we are still at least a decade away from cloaking objects from visible light.

It will be difficult to cover the whole visible spectrum. An object would be encased in a shell of metamaterials and they would create an illusion akin to a mirage, said David Schurig of Duke University in North Carolina, who worked on the second report. The light rays end up behind the object as if they had traveled in a straight line.

Cloaking could be used on space probes to protect sensitive equipment from cosmic radiation.

May 25, 2006

Carbon nanotubes collapse with powerful force to extrude and squeeze metal wire

Carbon nanotubes collapse with powerful force when bombarded by electrons and have potential as nanoscale extruders, cylinders, and jigs Engineers use a variety of tools to manipulate and process metals. For example, handy "jigs" control the motion of tools, and extruders push or draw materials through molds to create long objects of a fixed diameter. The newly reported findings suggest that nanotubes could perform similar functions at the scale of atoms and molecules, the researchers say. In the experiments, nanotubes withstood pressures as high as 40 gigapascals, just an order of magnitude below the roughly 350 gigapascals of pressure at the center of the Earth. The researchers filled carbon nanotubes with nanowires made from two extremely hard materials: iron and iron carbide. When irradiated with an electron beam, the collapsing nanotubes squeezed the materials through the hollow core along the tube axis, as in an extrusion process. In one test, the diameter of iron carbide wire decreased from 9 nanometers to 2 nanometers as it moved through the tube, only to be pinched off when the nanotube finally collapsed. This picture shows an iron carbide wire thinning as it moves through the nanotube as the wire collapses.Iron carbide wire thinning and collapsing from pressure from carbon nanotube

china announces military modernization plans

New study suggests Invisibility metamaterials possible in 5 years

Precise and creative control of material below the wavelength of a radiation (like visible light 390 to 780 nanometers) can be used to create invisibility. Better nanoprecise materials help facilitate this. radio and radar wave invisibility is projected for 18 months and visible light in 5 years.

Pendry and his co-authors also propose using metamaterials because they can be tuned to bend electromagnetic radiation - radio waves and visible light, for example - in any direction. A cloak made of those materials, with a structure designed down to the submicroscopic scale, would neither reflect light nor cast a shadow.

Instead, like a river streaming around a smooth boulder, light and all other forms of electromagnetic radiation would strike the cloak and simply flow around it, continuing on as if it never bumped up against an obstacle. That would give an onlooker the apparent ability to peer right through the cloak, with everything tucked inside concealed from view.

Already the scientists are a long way towards the easier goal of creating a cloak that can render objects invisible to radar or radio waves. Both have longer wavelengths than visible light, making them less challenging to work with.

"We are confident we can build a cloak that will work for radar within 18 months," said Prof Pendry, one of the authors of a research paper published today in the journal Science.

Here is the abstract at the journal Science, on Metamaterials and Negative Refractive Index. the article discusses the potential that these materials may hold for realizing new and seemingly exotic electromagnetic phenomena.

Here is some background on metamaterials

other tech: Improvements in superconducting wire and wire production

May 24, 2006

Challenges making bulk carbon nanotubes strong enough for a space elevator

Researcher predicts that carbon nanotubes will have trouble getting more than 30 GPa of strength Laboratory tests have shown that individual nanotubes can withstand an average of about 100 GPa, an unusual strength that comes courtesy of their crystalline structure. But if a nanotube is missing just one carbon atom, this can reduce its strength by as much as 30%. And a bulk material made from such tubes is even weaker. Most fibres made from nanotubes have so far had a strength much lower than 1 GPa. Using a mathematical model that he has devised himself, and which has been tested by predicting the strength of materials such as nano-crystalline diamond, Pugno calculates that large defects will unavoidably bring a cable's strength below about 30 GPa.

Bradley Edwards, whose space elevator feasibility study for NASA and a subsequent book have made him the most frequent spokesman for the space elevator project. Edwards, who is president and founder of the Dallas-based company Carbon Designs, shrugs off the controversy, and says that with adequate funding he could make cables at or above the 62-GPa benchmark in just three years. He suggests that the key step is carefully spinning long nanotubes together in a close-packed way, which encourages cooperative frictional forces that make the strengths of individual nanotubes less crucial.

I think the space pier concept is superior. Achieving the goal of very cheap launches to orbit without having and maintaining the maximum material strength. A space pier only needs 5 GPa strength material. M5 Fiber is that is already strong enough for a space pier

Space elevators on the moon and mars would still be easy. Long skyhooks could be made to take cargo from space planes going to 100km.
High Altiture Long Endurance platforms can be made better with progressively better tethers and climbers that are being developed for the space elevator

May 23, 2006

Nanowires stabilized by water could achieve 10,000 terabits per cubic centimeter

Ultra dense nanowire memory is possible Spanier as estimating the density of computer memory drives made of nanowires to be 10,000 terabits of data per cubic centimeter as opposed to the five gigabits per cubic centimeter of current flash memory drives. It's probably going to be fairly long before this can be achieved, however. Spanier predicts in the near future the development of new types of chemical sensors, emerging from the study of the interaction of a variety of molecules with nanoscaled ferroelectrics and ultra thin films.

Other article, discussing that a cubic centimetre of ferroelectric memory could hold as much as 12.8m GB of data.

Researchers at Drexel University and the University of Pennsylvania, both in Philadelphia, and Harvard University in Massachusetts, US, discovered that water turns barium titanate (BaTiO3) nanowires into a potential form of computer memory. The New Scientist magazine site was one of the first to discuss this development

May 22, 2006

other tech: Radically improved thermophotovoltaics (TPV) could provide efficient power for car sub-systems

The research is applying new materials, new technologies and new ideas to radically improve an old concept -- thermophotovoltaic (TPV) conversion of light into electricity. Rather than using the engine to turn a generator or alternator in a car, for example, the new TPV system would burn a little fuel to create super-bright light. Efficient photo diodes (which are similar to solar cells) would then harvest the energy and send the electricity off to run the various lighting, electrical and electronic systems in the car.

Such a light-based system would not replace the car's engine. Instead it would supply enough electricity to run subsystems, consuming far less fuel than is needed to keep a heavy, multi-cylinder engine running, even at low speed. Also, the TPV system would have no moving parts; no cams, no bearings, no spinning shafts, so no energy would be spent just to keep an engine turning over, even at idle.

It definitely the best system for running any subsystems like air conditioning, radio, tv and other electronics etc... It looks like a good fit for hybrid cars.

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