Nanotechnology News Network

Cell Repair Nanorobot Design And Simulation

In this study I'll try to simulate simple mobile cell-repair nanorobot and try to analyse some kind of it's subsystems. A complete functional design of an artificial cell-repairer is beyond the scope of this paper. Here, I want to focus on the purely simulation aspects of the cell repair nanorobot's functions and parts.

What kind of robot will be this nanomedical device?

Due to it's functions in human bloodstream and tissues it must be mobile and have powerful navigation system.

It may have a wide range of sensors to navigate through human body and to fast molecular and cell identification.

It may have powerful transport subsystem to molecular deliver system (it must deliver molecules and atoms to the working nanomanipulators from storage systems).

Wide range of computer-guided nanomanipulators also required.

It may be manufactured from flawless diamondoid due to biocompability with human body.

It may have broadcasting system which can connect to other nanorobots and to macrocomputers.

Finally, it may have long telescopic manipulators to holding cells or surfaces.

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Some excellent background on Nanotubes culled from PhysicsWeb

Carbon nanotubes roll on

Nanotubes have an impressive list of attributes. They can behave like metals or semiconductors, can conduct electricity better than copper, can transmit heat better than diamond, and they rank among the strongest materials known - not bad for structures that are just a few nanometres across. Several decades from now we may see integrated circuits with components and wires made from nanotubes, and maybe even buildings that can snap back into shape after an earthquake.

More about nano tubes from Physics World...

Euler was the first to calculate what happens to a rod when it is compressed along its length (so-called axial compression). Initially the rod remains straight as the compression increases, before flipping into a curved form at the Euler limit. If this experiment is performed with a drinking straw at constant load, the straw will suddenly develop kinks, which remain if the load is removed. In other words, the kinks are plastic rather than elastic deformations.

Carbon nanotubes are different: first they will bend over to surprisingly large angles, before they start to ripple and buckle, and then finally develop kinks as well. The amazing thing about carbon nanotubes is that these deformations are elastic - they all disappear completely when the load is removed.

To see how these properties might be useful, imagine owning a BMW car made from carbon nanotubes and being unlucky enough to crash into a wall. Due to the high force of the impact, the nanotubes would bend and then buckle, squeezing your BMW into the shape of something like a Volkswagen Beetle. This would happen over a relatively long distance, which would provide an effective "crunch zone". Moreover, after the crash all the buckles and kinks would unfold and your BMW would "reappear" as if nothing had happened! To be completely safe, however, the nanotubes would have to be combined with energy-absorbing materials, otherwise the collision between the car and the wall would be completely elastic and you would rebound from the wall with the same speed as you hit it!

Nanotubes switch back and forth

Two groups of physicists have shown that carbon nanotubes respond to magnetic fields in ways that are not seen in other materials. Junichiro Kono and colleagues at Rice University and Florida State University and Alexey Bezryadin and co-workers at the University of Illinois at Urbana-Champaign have discovered that semiconducting nanotubes can be made metallic, and vice versa, by applying a magnetic field. In addition to their fundamental importance, the results could have practical applications (Science 304 1129 and 1132).

Carbon nanotubes are essentially rolled up sheets of graphite, just nanometres in diameter, that can be metallic or semiconducting depending on the direction in which the sheet has been rolled up. Kono and co-workers performed optical absorption and emission spectroscopy on solutions of semiconducting single wall nanotubes placed in strong magnetic fields of 45 Tesla. They found that the band gap between the conduction and valence bands in the nanotubes became smaller as the strength of the magnetic field was increased.

"This phenomenon is unique among known materials," Kono told PhysicsWeb. "Ordinary semiconductors show the opposite behaviour." The team believes that the band gap could disappear completely in higher fields, which would cause the semiconducting nanotubes to become metallic.

Meanwhile, Bezryadin and colleagues found that the band gap in a multi-walled metallic nanotube -- which was initially zero -- gradually widened as a magnetic field was applied, turning it into a semiconductor. Moreover, as the applied field was increased further, the band gap dropped back to zero and the nanotube became a metal again.

Although these effects have never been observed in nanotubes before, they agree with theoretical predictions. Both experiments also highlight the importance of a subtle quantum effect known as the Aharonov-Bohm effect. Although this effect has been observed in many systems before, including nanotubes, this is the first time that it has been shown to have an effect on the band structure of a solid.

"The discovery could lead to novel magneto-optical or magneto-electrical switching devices by magnetically controlling the metallicity of nanotubes," Kono told PhysicsWeb. "It could also lead to novel experiments on one-dimensional systems."

"Our work demonstrates that hollow molecules can change the energies of their orbitals in response to the magnetic flux threaded through the molecule," said Bezryadin. "This observation may have interdisciplinary importance, since electronic orbitals not only determine the energy of the molecule but also its chemical, mechanical and other properties. It might therefore be possible to control these properties by a magnetic field."

Kono's group now plans to study the effects of even stronger magnetic fields on nanotubes, while Bezryadin and co-workers will repeat their experiment at ultracold temperatures to obtain an even clearer picture of how the electron energy levels in the nanotubes respond to magnetic fields.

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Responsible Nanotechnology: Nanotechnology in Japan


Starting in 1992 (the year Eric Drexler published Nanosystems), Japan spent a decade developing the foundations for bottom-up nanotech. They worked on four things:

1. "identification and manipulation of atoms and molecules" -- Obviously of great importance for bottom-up nanofabrication.

2. "formation and control of nanostructures on the surface and at the interface of materials" -- Likewise, very important.

3. "spin electronics" -- I'm not sure why this was in there; possibly to provide a short-term profitable spinoff (no pun intended).

4. "theoretical analysis of the dynamic processes of atoms and molecules" -- This sounds like research into bonding, and quite possibly relevant to mechanochemistry.

The leader, Kazunobu Tanaka, designed a highly interdisciplinary and collaborative working environment. He called for strong university participation. He put together a laboratory with 100 scientists sharing facilities, including cafeteria and relaxation room. He also recommends active use of sabbatical leaves and flexible university curriculums.

According to one article, "Dr. Tanaka says nanotechnology in Japan will not make any progress unless project leaders and researchers with a wide outlook are brought up. He adds that the master plan for developing nanotechnology in Japan should be discussed from the mid- and long-term viewpoint by young researchers with strong physical and intellectual ability."

This sounds to me like a very effective process for developing advanced technology. And this is not just theory; it's been put into practice in a decade-long foundational project that finished two years ago. Japan has now put hundreds if not thousands of research-years into bottom-up fabrication. And they've had plenty of time to think about the implications and applications.

I'm encouraged that they appear to be socially conscious. The reason for the sabbaticals is to allow the researchers to "reconfirm the positioning of their own studies in society." And the purpose of the flexible university curriculums is "to respond quickly to changing times and to meet current social needs."

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Carbon-50 makes its debut

PhysicsWeb, 29 April 2004

Physical chemists in China have made carbon-50 molecules in the solid state for the first time.

Lan-Sun Zheng and colleagues at Xiamen University, and co-workers at the Chinese Academy of Sciences in Beijing and Wuhan, prepared the molecules - which they describe as a long sought little sister of carbon-60 - in an arc-discharge technique involving chlorine.

The result will allow scientists to study the properties of carbon-50 with a view to exploiting its unusual properties. The method developed by the Chinese team also opens the way to making other small, cage-like carbon molecules or "fullerenes" (S-Y Xie et al. 2004 Science 304 699).

The most common fullerene is carbon-60 - also known as buckminsterfullerene or "buckyball". This molecule, which contains 60 carbon atoms arranged in a spherical structure made up of pentagons and hexagons, was first created in 1985. Since then larger fullerenes containing between 70 and 500 carbon atoms have also been produced.

All the fullerenes made so far obey the isolated pentagon rule (IPR): this rule states that the most stable molecules are those in which every pentagon is surrounded by five hexagons. However, it is not possible to satisfy this rule in a molecule with fewer than 60 carbon atoms. This means that so-called non-IPR fullerenes should have unusual properties, but it also makes them structurally unstable and difficult to synthesise. Until now, fullerenes with fewer than 60 carbon atoms have only ever been made in the gas phase.

Zheng and colleagues succeeded in stabilising and capturing solid-state carbon-50 molecules using a graphite arc-discharge method. They added 0.013 atmospheres of carbon tetrachloride vapour to 0.395 atmospheres of helium in a sealed stainless steel vessel and then applied an electric field of 24 Volts. After purifying around 90 grams of soot that contained carbon-50 chloride (C50Cl10), they obtained about 2 milligrams of C50Cl10 that was 99.5% pure.

"The C50Cl10 looks like a spacecraft or a spinning planet with 10 reactive carbon-chlorine arms ready for further chemical functionalization," team member Su-Yuan Xie told PhysicsWeb (see figure). Like derivatives of carbon-60 and 70, Xie says that carbon-50 could easily react with a variety of organic groups to form new compounds with interesting chemical and physical properties. Moreover, the technique could also be extended to synthesise other small fullerenes, such as carbon-54 and carbon-56.

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New Spin On Computing

Information Week, Antone Gonsalves, TechWeb News, April 26, 2004

IBM and Stanford University on Monday launched a joint research center focused on an area of nanotechnology called "spintronics," which could one day end the irritating delay people experience when they turn on their computers.

Spintronics involves use of the spin property of electrons--tiny particles in atoms that produce electricity when flowing through a conduit. Controlling the spin of electrons within a computer's CPU, the chip that provides processing power, is how researchers hope to create the fast-loading computer as well as other enhancements.

IBM and Stanford disclosed the formation of the Spintronic Science and Applications Center, or SpinAps, at IBM's Almaden Research Center in San Jose, Calif. Spintronics research will be conducted at Almaden and at Stanford's labs. However, IBM and Stanford researchers don't expect to see commercial products using their work for five to 10 years.

Most of today's electronic research focuses on the ability of electrons to carry an electrical charge. By focusing on an electron's spin properties, IBM and Stanford researchers hope to make breakthroughs in chip design, an IBM spokesman said.

The new design involves stacking layers of material, two or three atoms thick, to control the spin of electrons as they travel through the layers. Among the benefits would be the creation of magnetic random access memory.

RAM is where the computer loads the software needed to run when the machine is turned on. It's this process that takes time. In addition, when the computer is turned off, everything in RAM disappears, which means the process has to be repeated.

Magnetic RAM, on the other hand, would remain on, even when the computer is shut off, which means computer-launching software would be saved. As a result, turning on a computer would immediately take it to its previous state.

"RAM is volatile, which means if you shut down the power, then the information is gone," the spokesman said. "What spintronics allows you to do is set state through electron-spin interaction, so (the chip) doesn't need power to keep the information."

In addition, magnetic RAM won't leak power like the RAM used in today's computers. Because of power leakage, computers have to constantly reload RAM with the software needed to keep the machine running.

"It's like having a leaky bucket, and you have a faucet on to keep the level of water the same," Ross said. "The power is like the faucet. You have to keep it on as the power leaks out."

Eliminating this inefficient power usage means a laptop will run longer on its battery, and computer makers would be able to find new ways to use the power that will no longer be needed for RAM, Ross said.

Spintronics is a field within nanotechnology, the science of developing materials at the atomic and molecular level in order to imbue them with special electrical and chemical properties. Nanotechnology is expected to make major contributions to the fields of computer storage, semiconductors, biotechnology, manufacturing and energy.

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Soldering iron added to nano-toolkit

New Scientist

An atomic-scale conveyor belt may also be the smallest soldering iron ever created. The new device, which ferries molten metal, is made from carbon nanotubes just 20 millionths of a millimetre in diameter.

The discovery could pave the way for nano-machines that are pieced together from smaller components, rather than emerging from chemical reactions.

"There has been a dream for many years to build nano-structures piece by piece, like building a large-scale machine," explains Alex Zettl, who built the nano-soldering iron at the University of California in Berkeley. Then the structure is no longer constrained by the chemistry of its components, he says.

Currently, nano-probes can nudge atoms one at a time from one place to another. But to generate the flow of molten material necessary to solder parts together, hundreds of thousands of atoms must be moved.

Zettl begins by spraying pure carbon nanotubes with gaseous indium. The metal then condenses into solid droplets between one and 10 nanometres wide. Using a nano-manipulator built in his lab he connects the tubes to a circuit and applies a small voltage.

Heat from the resulting current melts the droplets, which scurry along the nanotube's surface and collect as a bubbling liquid at the negative end. Reversing the voltage shunts indium to the other end, meaning the movement is driven by electricity rather than a thermal effect. And varying the voltage changes the flow of liquid indium from a "drip-drip" to a "surge", Zettl says.

The liquid bubbles could be wicked off the ends of the tubes and used to solder tiny parts together, he says, though this has yet to be demonstrated.

Zettl is unsure why neutral indium atoms move in response to a voltage. "It looks like the indium is being positively charged," he says. He suggests that electrons may be migrating from the indium to the nanotubes.

Droplets of gold, tin and platinum can also be made to move from one end of the tube to the other. "It's the first time we have controllable, atomic scale motion of mass," Zettl told New Scientist.

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