Technology Trends

Gecko lizards, which can climb any vertical surface and hang from a ceiling with one toe, have fascinated scientists for a long time. Their foot-hairs have a structure which allow them to strongly adhere to any type and shape of surface. Now, according to this short news release from the National Science Foundation (NSF), researchers from the University of Akron, Ohio, have developed synthetic hairs from multiwalled carbon nanotubes (MWNT) that have adhesion forces 200 times higher than those observed with gecko foot-hairs. This could lead to new dry adhesives used in microelectronics, robotics or space applications. Read more…

Here is the first paragraph of the NSF press release (here is another link if you want to see a picture of a gecko lizard).

Renowned for their ability to walk up walls like miniature Spider-Men–or even to hang from the ceiling by one toe–the colorful lizards of the gecko family owe their wall-crawling prowess to their remarkable footpads. Each five-toed foot is covered with microscopic elastic hairs called setae, which are themselves split at the ends to form a forest of nanoscale fibers known as spatulas. So when a gecko steps on almost anything, these nano-hairs make such extremely close contact with the surface that they form intermolecular bonds, thus holding the foot in place.

So researchers from the University of Akron, helped by a $400,000 grant from the NSF, have developed synthetic hairs from carbon nanotubes that have adhesion forces 200 times higher than those observed with gecko foot-hairs. Here is a link to their own news release.

They built new structures, based on multiwalled carbon nanotubes (MWNT) constructed on polymer surfaces with strong nanometer level adhesion. These structures can be used as dry adhesives similar to or stronger than gecko foot-hairs.

Here is an example of such nanostructures.

The pictures above illustrate the topography and force measurement of multiwalled carbon nanotube brushes on PMMA with a scanning force microscope (SPM). (A) and (B) show real SPM height images taken by tapping mode for vertically and horizontally aligned MWNT, respectively. The bars represent 5 nm and 150 nm, respectively (Credit: University of Akron).

[Note:PMMA, which stands for Poly(methyl methacrylate), is a transparent plastic sold under different names, such as Plexiglas, and is often simply called Acrylic.]

The research paper about this work has been published by Chemical Communications on July 5, 2005 under the title “Synthetic gecko foot-hairs from multiwalled carbon nanotubes” (Issue 30, 2005, Pages 3799 - 3801). Here is a link to the short abstract.

We report a fabrication process for constructing polymer surfaces with multiwalled carbon nanotube hairs, with strong nanometer-level adhesion forces that are 200 times higher than those observed for gecko foot-hairs.

The full paper is available for free for registered users of the Institute of Physics for a duration of one month. Here is a link to this paper (PDF format, 3 pages, 313 KB).

For more information, you also can read a previous entry about a related project, “Spider Legs Lead to Better Post-it Notes.”

These two projects don’t follow the same approach, but they have a similar goal: design improved adhesives that will have critical applications in microelectronics, information technology, robotics, space and other areas.

Sources: National Science Foundation news release, via EurekAlert!, August 15, 2005; and various web sites

Related stories can be found in the following categories.

• Chemistry
  


• Materials
  


• Nanotechnology
  


• Nature
  


• Science
  

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Scientists at the University of Manchester, in the UK, have discovered a new class of materials which are one atom thick and exhibit properties previously never thought possible. With these new materials, they are promising us a ‘new industrial revolution.’ Not only these new materials are ultra-thin, but they can also be ultra-strong, highly-insulating or highly-conductive. Apparently, this new class of materials has been validated by the scientific community, and even if some applications are probably decades away, you can expect to see ‘ultra-fast transistors, micromechanical devices and nano-sensors based on the discovered one-atom-thick crystals already in a few years time.’ Read more…

Here is the introduction of the news release from the University of Manchester.

Scientists at The University of Manchester have discovered a new class of materials which have previously only existed in science fiction films and books.

A team of British and Russian scientists led by Professor Andre Geim, [director of the Manchester Centre for Mesoscience and Nanotechnology,] have discovered a whole family of previously unknown materials, which are one atom thick and exhibit properties which scientists had never thought possible.

After this press release lingo, let’s move — gradually — to some more technical details.

The materials have been created by extracting individual atomic planes from conventional bulk crystals by using a technique called ‘micromechanical cleavage’. Depending on a parent crystal, their one-atom-thick counterparts can be metals, semiconductors, insulators, magnets, etc. Previously, it was thought that such thin materials could not exist in principle, but the research team have, for the first time, demonstrated that they are not only possible but fairly easy to make.

Below are some pictures of these very small two dimensional crystals (Credit for images and legend: University of Manchester).

[Here you can see] single-layer crystallites of (a) NbSe₂, (b) graphite, (c) Bi₂Sr₂CaCu₂O_x and (d) MoS₂ visualized by AFM (a,b), SEM (c) and in an optical microscope (d). All scale bars are 1µm.

Dr Kostya Novoselov, a key investigator in this research, added: “Probably the most important part is that our discovery is not limited to just one or two new materials. It is a whole class of new materials, thousands of them. And they have a variety of properties, allowing one to choose a material most appropriate for a particular application.

This fascinating research work has been published by the Proceedings of the National Academy of Sciences (PNAS) in its July 18, 2005 issue under the name “Two-dimensional atomic crystals.” Here is a link to the abstract.

We report free-standing atomic crystals that are strictly 2D and can be viewed as individual atomic planes pulled out of bulk crystals or as unrolled single-wall nanotubes. By using micromechanical cleavage, we have prepared and studied a variety of 2D crystals including single layers of boron nitride, graphite, several dichalcogenides, and complex oxides. These atomically thin sheets (essentially gigantic 2D molecules unprotected from the immediate environment) are stable under ambient conditions, exhibit high crystal quality, and are continuous on a macroscopic scale.

And here is a link to the full paper from which the above figure has been extracted. Below is the conclusion of this paper.

We have demonstrated the existence of 2D atomic crystals that can be prepared by cleavage from most strongly-layered materials. It is most unexpected if not counterintuitive that isolated 2D crystals can be stable at room temperature and in air, leaving aside the fact that they maintain macroscopic continuity and such high quality that their carrier mobilities remain almost unaffected. The found class of 2D crystals offers a wide choice of new materials parameters for possible applications and promises a wealth of new phenomena usually abundant in 2D systems. We believe that, once investigated and understood, 2D crystals can also be grown in large sizes required for industrial applications, matching the progress achieved recently for the case of single-wall nanotubes.

Finally, even if these new materials are only one atom thick, they still have three dimensions. The idea of 2D crystals and materials in our 3D world would be too disturbing. What do you think of these discoveries? Can we really talk about ‘flat’ materials? And will this research lead to a new industrial revolution? Please post your comments below.

Sources: University of Manchester news release, July 18, 2005; and various web sites

Related stories can be found in the following categories.

• Future
  
  
• Materials
  
  
• Nanotechnology
  
  
• Physics
  
  
• Science
  

A team of chemists from the University of California at Los Angeles (UCLA) has built the world’s first nano valve. This device can trap and release molecules on demand. This mechanical system can control molecules like a water faucet you can open or close at wish. This nano valve has moving parts — switchable rotaxane molecules — attached to a piece of porous glass, with pores only a few nanometers in size. As this nano valve is much smaller than living cells, we can imagine a day when we swallow a nano valve combined with bio-molecules to release drugs inside our bodies. But the full potential of artificial molecular machines will take a long time to materialize. Read more…

“With the nano valve, we can trap and release molecules on demand. We are able to control molecules at the nano scale,” said Jeffrey I. Zink, a UCLA professor of chemistry and biochemistry, a member of the California NanoSystems Institute at UCLA, and a member of the research team.

The image below shows how the nano valve works. And here is a link to a larger version of this diagram.

[On this picture,] “a” shows the structural formula of the rotaxane molecule and the procedure for tethering it to the surface of a tiny piece of glass while “b” shows how the nano valve opens and closes (Credit for image and legend: UCLA).

Now, here are more technical details about this nanofaucet.

This nano valve consists of moving parts — switchable rotaxane molecules that resemble linear motors designed by California NanoSystems Institute director Fraser Stoddart’s team — attached to a tiny piece of glass (porous silica), which measures about 500 nanometers, and which Thoi Nguyen is currently reducing in size. Tiny pores in the glass are only a few nanometers in size.

The valve is uniquely designed so one end attaches to the opening of the hole that will be blocked and unblocked, and the other end has the switchable rotaxanes whose movable component blocks the hole in the down position and leaves it open in the up position. The researchers used chemical energy involving a single electron as the power supply to open and shut the valve, and a luminescent molecule that allows them to tell from emitted light whether a molecule is trapped or has been released.

The research work has been published in the July 19, 2005 of the Proceedings of the National Academy of Sciences as an “open access article” under the name “A reversible molecular valve.” Here is a link to the abstract.

In everyday life, a macroscopic valve is a device with a movable control element that regulates the flow of gases or liquids by blocking and opening passageways. Construction of such a device on the nanoscale level requires (i) suitably proportioned movable control elements, (ii) a method for operating them on demand, and (iii) appropriately sized passageways.

These three conditions can be fulfilled by attaching organic, mechanically interlocked, linear motor molecules that can be operated under chemical, electrical, or optical stimuli to stable inorganic porous frameworks (i.e., by self-assembling organic machinery on top of an inorganic chassis).

In this article, we demonstrate a reversibly operating nanovalve that can be turned on and off by redox chemistry. It traps and releases molecules from a maze of nanoscopic passageways in silica by controlling the operation of redox-activated bistable [2]rotaxane molecules tethered to the openings of nanopores leading out of a nanoscale reservoir.

And if you really want to read more about this molecular valve, here is a link to the full paper (PDF format, 6 pages, 495 KB). But if you’re not a chemist, I doubt you’ll understand the contents.

I’ll leave the last words to Fraser Stoddart.

“Building artificial molecular machines and getting them to operate is where airplanes were a century ago,” Stoddart said. “We have come a long way in the last decade, but we have a very, very long way to go yet to realize the full potential of artificial molecular machines.”

And now, I’m waiting for your own comments: what do you think of these future molecular machines?

Sources: UCLA news release, July 15, 2005; and various web sites

Related stories can be found in the following categories.

• Biotechnology
  
  
• Chemistry
  


• Medicine
  


• Nanotechnology
  

Nanoscientists and food industry specialists are meeting right now at Nano4Food 2005, a conference held in Wageningen, The Netherlands, on June 20-21. They will discuss how nanotechnology can help food processing companies to improve the safety and quality of their products by using nanosensors and diagnostic machines. But, in this article, FoodProductionDaily.com writes that there is another subject on the agenda. New kinds of foods, embedded with nanoparticles, could one day deliver their contents in our bodies, such as medicines or nutrients. So far, food companies are only investigating, and no product has been released yet. But technology is almost ready for these companies to sell you interactive drinks you can play with, changing colors or textures. Read more…

Let’s start with a financial forecast from an analyst — who certainly never ate nanofood. And don’t forget to read this again in 2010!

The nanofood market is expected to rise from $2.6bn today to $7bn next year and to $20.4bn in 2010 according to a study by consultant Helmut Kaiser.

Please notice that ‘nanofood market’ doesn’t mean edible food. And this brings us back to how nanotechnology can be used for food safety.

On the processing line nanotechnology can be used to create tiny sensors and diagnostic machines that can help ensure food does not leave the factory with contaminants. Such nanodevices can also help processors detect harmful microbes and determine the shelf life for their foods. Such fine scale detection could help food processors make strategic decisions, such as the best transportation method for their products and storage methods, said Frans Kampers [, the program manager of bio-nanotechnology at Wageningen University.]

“The use of nanotechnology to ensure the quality of a food product has obvious benefits for consumers,” he said. However, such robotic nanosensors and detectors are still being developed in food processing and research laboratories. Kampers forecasts that the first such machines will appear on the food production line within four years.

On the other hand, incorporating nanoparticles in our food is an entirely different story.

Researchers generally refer to nanofoods as being embedded with either “soft particles”, those using common biological materials or with “hard particles”, made up of non-organic substances.

“Soft particles” might be harmless to us, because our bodies can recognize them. But what about these “hard particles”?

Here the work is more speculative as the body is not used to ingesting and processing such substances, even if they are so tiny. As they are so tiny, nanoparticles exhibit different chemical behaviour than would normally be found in larger masses of material. Quantum mechanics, the behaviour of particles and surfaces at the microscopic level, comes into play.

“We do not really know exactly how these nanoparticles go through different routes in the body and where they end up,” said Kampers. “We need more research about the effects on food and on the body.”

So will we soon eat nanofoods? A long article from the Observer, U.K., about the cutting edge of food technology, published in May 2004, already mentioned that “food technologists are dreaming up ever new ways of feeding us — and the future is any colour you want.” Here is a selected quote.

Manuel Marquez-Sanchez [, a scientist at Kraft Foods,] has big hopes for nanotechnology. By manipulating ingredients at the nano level, and storing them in ‘nanocapsules’, he believes that Kraft will be able to devise such treats as an interactive, customisable drink. ‘The idea is that everyone buys the same drink, but you’ll be able to decide its colour, flavour, concentration and texture,’ he explains enthusiastically. ‘Once you have a technology to design nanocapsules, based on food-grade materials, you can offer products that put the consumer in control.’ Although the industry, one presumes, will wish to retain control of everything from labelling requirements and costs to the degree of prior safety testing.

So what do you think? Are you really ready for nanofood or not?

Sources: Ahmed ElAmin, FoodProductionDaily.com, June 17, 2005; and various web sites

Related stories can be found in the following categories.

• Biotechnology
  


• Environment
  


• Food
  


• Medicine
  


• Nanotechnology
  

The European Space agency (ESA) launched its Innovation Triangle Initiative in March 2004. The goal was to speed up the turnaround time from an idea to a product by creating a close collaboration between inventors and developers. Today, 27 space projects have been validated, “pioneering technology to explore other planets.” One of these projects is focused on smart new textiles, designed to be the basic building blocks of large structures to be deployed in space, such as future solar sails. Read more…

This specific project, completed in about nine months, combined the expertise in elastomers of the Cavendish Laboratory of Cambridge University in the UK, and the skills of two European companies, NTE in Spain, which already built large structures in space, and Grado Zero Espace in Italy for its knowledge of ‘intelligent’ textiles.

For example, below is a cooling jacket for astronauts who have to deal with high temperatures occurring during sun exposure in open space (Credit: Grado Zero Espace for its parent company, Corpo Nove). This jacket incorporates 50 meters of plastic tubing, each being 2 mm wide.

The company also designs I.O.W. (Intelligent Object to Wear), such as this motorbike jacket with its internal heating mechanism (Credit: Grado Zero Espace for its parent company, Corpo Nove).

Inside the jacket lining is a computerized microprocessor with hard disk (no bigger than a packet of cigarettes) which controls the body temperature over a series of electric heating pads.

Now, it’s time to look in details to how ’smart’ textiles can help space exploration, with some excerpts of the ESA news release.

In the future, huge ’sails’ powered by solar particles could be used to push spacecraft through space, in the same way that sails power yachts through the sea. Solar sails would have to cover an area of at least 10 000 square metres and need ultra-light and extremely large rigid structures of booms to hold them in place, a feat difficult to realise with today’s techniques.

The Italian company Grado Zero Espace came up with the idea of using an ‘intelligent’ textile to construct the extremely light and very long deployable booms that would be needed. The textile would be created by combining state-of-the-art materials and technologies such as carbon nanotubes, novel rubber-like materials named ‘nematic elastomers’ and special three-dimensional warp-knitted textile-based membranes.

Nematic elastomer composites are prepared by spreading carbon nanotubes on to a rubber matrix, with the nanotubes pre-aligned in one preferential direction. Due to this alignment of the fibres, the material’s properties are different along this direction. When an external electric field is applied, the nanotubes try to re-orient themselves and cause a change in shape of the whole rubber composite.

Finally, if you have an idea for a product which could be used in space, you still can submit a proposal to ESA’s Innovation Triangle Initiative which can provide you with seed money up to 150K euros.

Sources: ESA news release, June 16, 2005; and various web sites

Related stories can be found in the following categories.

• ESA
  
  
• Materials
  
  
• Nanotechnology
  
  
• Space
  
  
• Wearable
  

The Pittsburgh Post-Gazette reports that a robot combined with a swallowable camera could give doctors a better look inside the small intestine. This medical robot, dubbed ‘bugbot,’ is being developed at Carnegie Mellon University (CMU) in its NanoRobotics Laboratory. It will measure less than 800 nanometers in diameter and will transmit thousands of images during its trip inside yourself with its embedded camera. With the six legs attached to the microrobot, CMU researchers want to give more control to camera operators, such as coming back to a suspected lesion. This robot should be ready for human inspection within 2 to 3 years and opens the way for future nanorobots. Read more…

Here are the opening paragraphs of the Post-Gazette article.

The words “intestinal bug” could gain a whole new meaning if a Carnegie Mellon University engineer is successful in his efforts to develop a medical robot for examining the intestinal tract.

Metin Sitti, director of the NanoRobotics Lab, is developing a set of legs that could be incorporated into the swallowable camera-in-a-pill that has become available in the past four years for diagnosing gastrointestinal disorders in the small intestine.

The capsule camera snaps thousands of pictures as it makes its way slowly through the narrow tract, carried by the wave-like peristaltic motion that moves all contents through the intestines.

This picture, from Steve Mellon, of the Post-Gazette, shows Sitti with a prototype of his six-legged intestinal robot. And the newspaper has additional explanations about this robot in this graphical representation of intestinal locomotion.

So far, this robot is not really ready to explore your body.

[Sitti] has devised a simple, three-footed apparatus less than two-thirds of an inch in diameter to test its stopping power in flexible plastic tubes and, in preliminary testing in South Korea, in pig intestines. A six-footed apparatus for testing the inchworm-like locomotion has been assembled and will soon be ready for testing.

The legged devices thus far do not incorporate a camera and are not designed to be swallowed.

For more information about previous research on this subject, you can read more about Micro Swimming Robots at CMU’s NanoRobotics Laboratory.

Here are the goals of the project.

Developing a microrobot which can travel to currently inaccessible parts of the body and perform user directed tasks such as highly localized drug delivery and screening for diseases that are in their very early stages.

And here are the benefits expected by the researchers.

We envision this robot having the capability to swim to inaccessible areas in human body and perform complicated user directed tasks such as diagnosis of diseases at early stages and targeted drug delivery.

Now, let’s return to the Post-Gazette which tells us about the future of the ‘bugbot.’

If the gutbot proves feasible for the small intestine, other applications may await it in the colon. Though the colon can be visualized with a long, flexible colonoscope, the procedure is not a popular one. Sitti [and his fellow researchers] suggested it may someday be possible to use a legged camera introduced through the anus as a substitute for traditional colonoscopy. They emphasized, however, that such an application is still years away.

For that matter, Sitti said, it may be possible to someday equip an intestinal robot to perform surgeries beyond just biopsies. But for now, developing a robot that could improve diagnosis of digestive tract disease is the immediate concern.

Sources: Byron Spice, Pittsburgh Post-Gazette, May 30, 2005; and various websites

Related stories can be found in the following categories.

• Medicine
  


• Nanotechnology
  


• Robotics
  


• Vision and Visualization Apps
  

Scientists and the military often share a common quality: imagination. For example, in “US military ‘rocks’ spy world,” the Financial Times reports that the U.S. military is developing RFID sensors that will be installed in fake little rocks. These ‘rocks’ which will be the size of golf balls, will be sent from an aircraft and will detect enemies by ‘listening’ to them from 20 to 30 meters. These sensors should be operational within 18 months and they should be cheap enough to leave them on the battlefield after they completed their tasks. Read more…

RFID is being developed into many areas of use. RFID technology is slowly taking over the use of barcodes in many instances. However, there is still something to be said for using barcodes. Many businesses still utilize barcode printers and barcode readers as a way to manage their inventory. Is using RFID scanners better than barcode scanners? Perhaps, but that is something that has to be decided by the individual.

Here is some information picked from the short Financial Times article.

The devices, which would be no larger than a golf ball, could be ready for use in about 18 months. They use tiny silicon chips and radio frequency identification (RFID) technology that is so sensitive that it can detect the sound of a human footfall at 20ft to 30ft. The project is being carried out by scientists at North Dakota State University, which has licensed nano-technology processes from Alien Technology, a California-based commercial manufacturer of RFID tags for supermarkets.

It is an example of the increasing desire for the US military to co-operate with civilian industry and academic institutions in the development of battlefield technology that will reduce the risks to soldiers’ lives. Greg McCarthy, associate vice president at the university’s Center for Nanoscale Science and Engineering, said: “The military wants better sensing capability. People are being killed because someone’s sneaking up on a tent and blowing them up.”

The military don’t distribute many images of future technologies. This picture of RFID sensors hidden inside fake rocks comes from this page on Sci-Tech Today (Credit: unknown).

For — slightly — more information about this project, you can look at the Center for Nanoscale Science and Engineering (CNSE) site at North Dakota State University (NDSU), and especially to this page about MicroSensor Systems. Here is the introduction.

The MicroSensor Systems program (aka Ultra-Low Power Battlefield Sensor Communication Systems, ULPBSCS), is a Department of Defense funded program. This program built a Center of Excellence (COE) at NDSU devoted to wireless microsensor system research and development and to the production of wireless microsensor systems for dual (military and commercial) needs. A central component of the program is advanced rapid microelectronics fabrication technology transferred to the university from Alien Technology Corporation, for the purpose of microsensor fabrication.

I’m feeling somewhat frustrated not being able to give you more details or illustrations about this interesting concept. So, if you have more information about this project, please post your comments below. Thanks.

Sources: Jeremy Grant, Financial Times, May 26, 2005; and various websites

Related stories can be found in the following categories.

• Military Applications
  
  
• Nanotechnology
  
  
• RFID
  
  
• Sensors
  

In 2006, NASA plans to send in space the first prototypes of a ‘black box’ named Re-entry Breakup Recorder (REBR). These black boxes, conceptually similar to commercial aviation black boxes, are expendable and weigh about one kilogram according to Small Times. These micro spacecrafts will be attached to a main spacecraft and will separate from it when it re-enters the Earth’s atmosphere. The nanosensors, which will weigh only a few grams, will collect data, such as temperature or pressure and other data, and validate thermal protection systems for human missions. NASA plans to put similar nanosensors in the Crew Exploration Vehicle (CEV), NASA’s future replacement for the shuttle. And if everything goes fine, nanosensors will be used for explorations of the moon and might go to Mars around 2025. Read more…

Here is the introduction from Small Times.

A joint project of NASA and El Segundo, Calif.-based Aerospace Corp. will develop a “black box” that uses nanosensors weighing a few grams. The nanosensors will be used to gather data about flight vehicles re-entering the earth’s atmosphere from space. After the perilous high-speed part of re-entry, the black box will “phone home” and relay data by satellite prior to impact with land or sea. The black box will be especially useful in the event of what NASA scientists call an “uncontrolled re-entry.”

And here are some of the reasons why NASA is looking at nanotechnology.

“The black box is a companion spacecraft that is attached to the main spacecraft and there could be more than one,” said Dan Rasky, a scientist at NASA’s Ames Research Center in Silicon Valley. “It’s designed with a heat shield to be able to survive a re-entry and take data of interest at re-entry, such as vehicle position or temperature.”

Nanotechnology offers advantages critical to next-generation space travel, Rasky said. “The challenges we have with a small spacecraft are power and mass,” Rasky explained. Nanotechnology solutions are lightweight and low power. “There are a number of nanotechnology uses involving batteries with greatly improved performance and duty cycles.”

Below is a diagram of the Reentry Breakup Recorder, also known as the Black box. (Credit: The Aerospace Corporation)

And below is another diagram showing the packaging concept of the Black box. (Credit: The Aerospace Corporation)

You’ll find larger images of these diagrams (in Powerpoint format) on this page.

At the end of April 2005, NASA issued a press release which contains many more details, “Micro Spacecraft to Pave the Way for Future Space Exploration.”

NASA and its partner [, The Aerospace Corporation,] recently agreed to develop the first ‘black box’ for spacecraft and test a prototype of this device that will be based on technology that Aerospace has been working on for several years. The ‘black box’ is actually a very small ‘micro spacecraft’ that would be attached to larger space vehicles. A joint program between NASA and Aerospace will develop the black box micro spacecraft, among many other low-cost, miniature space systems, under the terms of a NASA-Aerospace agreement.

NASA also looks at the future of these micro spacecrafts.

Scientists additionally envision using micro spacecraft to do systematic studies of Mars, and sample returns from the moon, Mercury and Venus. Micro spacecraft may also conduct “on location” studies of Venus. Because they can be less expensive than other, more complicated spacecraft, a great number of micro probes could be sent to many more places in the solar system to gather data, researchers suggest. The gas giant planets of Jupiter, Saturn, Uranus and Neptune offer countless opportunities for micro spacecraft to study ‘volatiles’ - water vapor, ammonia, various isotopes and winds.

Small Times, as well as NASA, are using extensively the word ‘nanotechnology.’ But here is the first paragraph of this news release from the Aerospace Corporation from February 2005.

The Aerospace Corporation and NASA Ames Research Center have signed a memorandum of understanding to collaborate on the development of new small, lightweight, low-cost reentry systems and related nano and pico spacecraft technologies, including miniature sensor systems.

Pico spacecraft technologies? WOW!!!

Anyway, without more details from NASA, it seems to me that these nanosensors belong more to the microscale than to the nanoscale dimension.

Sources: Richard Acello, Small Times, May 23, 2005; and various websites

Related stories can be found in the following categories.

• NASA
  
  
• Nanotechnology
  
  
• Sensors
  
  
• Space
  

Many announcements related to nanotechnology have been made last week, so I just want to make a quick summary. A team of chemists have found that buckyballs could have a negative impact on our environment while other researchers used nanotechnology to find tumors before they are visible in conventional MRI. A team at CMU could revolutionize nanoelectronics manufacturing by making ordered nanocarbons while a chemist at New York University thinks that DNA molecules could lead to the smallest computing devices ever built. Cornell University researchers have designed a nanoscale switch linking electronics to photonics and others at the University of Leeds, U.K., have identified antimicrobial nanoparticles for safer food packaging. In the commercial sector, Dimatix is developing nano-printing technologies which could lead to human skin cells, and Accelrys is using molecular modeling and simulation software tools to design potential new materials. Read more…

Please read all the articles or news releases mentioned above to find more information about these new discoveries. Here I just want to focus — briefly — on three of them.

Let’s first look briefly at this new use of nanotechnology to find tumors.

Biomedical engineers have used nanotechnology to find human melanoma tumors in mice while the growths are still invisible to conventional magnetic resonance imaging (MRI).

Earlier detection can potentially increase the effectiveness of treatment. This is especially true with melanoma, which begins as a highly curable disorder, then progresses into an aggressive and deadly disease.

A second benefit of the approach is that the same nanoparticles used to find the tumors could potentially deliver stronger doses of anti-cancer drugs directly to the tumor site with fewer side effects.

Now, here is a short description of the nano-printing technologies developed by Dimatix.

Dimatix currently employs about 50 people in its Santa Clara offices, where it is developing ink-jet printing technologies for a wide range of possible uses. Some futuristic uses of Dimatix’s super-small ink jets could include making semiconductor interconnects, or electronic screen displays so thin and flexible they wrap around a column in a department store.

Dimatix is developing a new generation of print heads that can deposit microscopic droplets of conductive ink, or even droplets of organic materials. They call these nano-particle inks, because they are at the atomic level in size, or smaller than a virus.

In the future, Dimatix expects its printing technologies to be used in the life sciences, where scientists could re-create human cells by layering down DNA substrates.

Finally, it’s time to look at the modeling software tools developed by Accelrys.

Here is the introduction of the article.

As electronics companies find themselves increasingly needing to characterise their materials at nanometre length scales, they are resorting to modelling software packages that until recently were seen as pure research tools.

Cambridge-based molecular modelling and simulation specialist Accelrys says its products, which are built on quantum mechanical descriptions of particular systems, are now being employed for real-world applications, rather than simply in more blue skies research.

Accelrys’ tools are typically applied in the fields of chemistry and fundamental materials science. They are used to address questions of what is happening at the molecular and atomic scales, and below, and enable the modelling of properties such as the electronic behaviour of solids, molecules, interfaces, and molecules on surfaces.

And here is the conclusion from Stephen Warde, European director of marketing for Accelrys.

“What our technology can help you do today is make smarter decisions about materials designs, and understand the materials science issues in more depth… I think it’s fair to say that we’re at the beginning of making those sorts of connections.”

And for more information about the involvement of Accelrys in this field, please read this page about Life Science Modeling.

Sources: American Chemical Society, May 9, 2005; The Whitaker Foundation, May 18, 2005; Carnegie Mellon press release, May 6, 2005; Spencer Reiss, Technology Review, June 2005; Cornell University news release, May 19, 2005; Food Production Daily, May 13, 2005; Therese Poletti, Mercury News, May. 16, 2005; Harry Yeates, ElectronicsWeekly.com, May 19, 2005; and various websites

Related stories can be found in the following categories.

• Chemistry
  


• Innovation
  


• Materials
  


• Medicine
  


• Nanotechnology
  


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Laser lights can be used for optical sensing applications, for example to identify unknown gases emitted by an engine. And as these unknown substances react differently to different wavelengths, researchers at the University of Wisconsin at Madison have developed unique wavelength-agile lasers. And I’m amazed by the beauty and the simplicity of their idea. They’re using white lasers which produce all colors simultaneously — but with a twist. The white laser light goes through a 20-kilometers long optical fiber before reaching its target. And because different colors ‘travel’ at different speeds, this produces independent results for the different wavelengths. The researchers are using spectral resolutions smaller than a thousandth of a nanometer and they are able to get all the results within a millionth of a second. This method could be used to design cleaner engines or data storage applications in a few years. Read More…

Let’s start with some technical explanations about this technology developed by Professor Scott Sanders in his labs.

Sanders’ laser builds on a phenomenon known as supercontinuum generation, in which researchers convert single-color lasers, such as a green or a red laser, into a multicolored beam using a special kind of optical fiber. Photonic crystal fibers enable them to generate this “white” laser beam, says Sanders.

While that method produces a range of laser colors-and thus, a large amount of information-the drawback is that the white laser delivers all of the colors simultaneously, says Sanders. Rather, researchers want to measure rapidly their subjects’ responses to individual colors.

So by directing the laser through an additional optical fiber about 20 kilometers long, Sanders created what he calls a “color-dependent speed limit.” Although all of colors leave the white laser at the same time, red travels through the fiber more quickly, while blue brings up the rear, and the rest of the colors fall somewhere in the middle. In photographs, they look like a continuous stream; in reality, each color exits the long fiber one after the other, like drops from a faucet. The entire laser scan occurs in a couple of millionths of a second.

Below is a photo showing how UW-Madison engine researchers gather useful data about the gases they study by using these wavelength agile lasers (Credit: UW-Madison College of Engineering).

Here is a link to a higher quality of this picture (3,264 x 2,448 pixels, 5.04 MB).

This research work about ‘rainbow’ lasers is making the cover story of Optics and Photonics News in its May 2005 issue. Full access to the paper (PDF format, 6 pages, 446 KB) is available via this page about “Wavelength-Agile Lasers.”

The figure below, which shows the evolution of wavelength-agile lasers within the author’s laboratory, has been extracted from this article (Credits: UW-Madison College of Engineering and Optics and Photonics News).

These colorful lasers should soon be used in such applications as spectroscopy or high-speed scanning.

Sources: University of Wisconsin at Madison, April 28, 2005; and various websites

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Today, anticancer drugs are delivered to patients in such a way that they can destroy both infected and healthy cells. But now, researchers at the Institute of Bioengineering and Nanotechnology (IBN), in Singapore, have designed ’smart’ nanocarriers which deliver the drugs exactly where they are needed, reducing side effects and suppressing cancer growth. Their core-shell nanoparticles are both sensitive to temperature — which has been done before — and to acidic levels. When these nanocarriers encounter acidic environments such as tumor tissues, they break apart and release the molecules they contain. So far, this technology has only been tested on mice, but the researchers have filed an application patent in the U.S., so expect to see practical applications in a few years. Read more…

Before going further, please note that this IBN news release, published by PhysOrg.com on April 26, 2005, was originally issued by IBN on March 21, 2005. You can find the original version here (PDF format, 2 pages, 49 KB).

So what’s the situation of anticancer drugs delivery today?

Anticancer drugs are now being administered to patients using methods that cause the indiscriminate killing of both diseased and healthy cells. [...] Hence, there is a crucial need for the development of more effective cancer therapy, which not only minimizes side-effects but also directly targets diseased cells.

Scientists at IBN have found a way to tackle this problem through the use of anticancer drug delivery vehicles that transport drugs only to where they are needed in the body. This method significantly reduces or even eliminates the severe side-effects typically induced by conventional chemotherapeutics.

So what exactly is this new method?

The team led by IBN Group Leader Dr Yi-Yan Yang has created ’smart’ nanocarriers that can house anticancer drugs in their inner cores. Such polymeric core-shell nanoparticles are small in size (generally less than 200 nm), with shells that protect enclosed bioactive compounds against degradation and digestive fluids.

These nanocarriers, which are both pH-sensitive and temperature-sensitive, are structurally stable in the normal physiological environment. However, in slightly acidic environments that are characteristic of tumor tissues and endosomes (a cell component), they deform and precipitate, thus releasing the enclosed drug molecules.

The key idea behind this new technology is obviously that these nanocarriers are pH-sensitive.

“Previous attempts by other scientists involved the use of core-shell nanoparticles that were only sensitive to temperature. Drug delivery may be controlled by superficially heating and cooling the environment of the nanoparticles,” said lead scientist Dr Yang.

“The novelty of our invention compared to carriers that are only temperature-sensitive is the ability of IBN’s core-shell nanoparticles to target drugs to deep tissues or cell compartments without changes in temperature.”

Now, two questions need to be answered: is this technology efficient? and does it suppress side effects?

So far, the IBN team has proven that their core-shell nanoparticles can deliver anticancer drugs much more efficiently into cancer cells, compared to current techniques. Their in vivo studies using a mouse breast tumor model has also shown that doxorubicin (an anti-cancer drug) loaded in these smart nanoparticles can suppress tumor growth more efficiently than free doxorubicin.

“IBN’s ’smart’ nanocarriers do not show significant cytotoxicity, and offer great potential in targeting drugs to tumor tissues with high efficacy,” added Dr Yang. “This invention may also be used in in vitro and animal studies for drug discovery.”

The research work has been published online by Advanced Materials on February 4, 2005(Volume 17, Issue 3, Pages 318-323) under the title “pH-Triggered Thermally Responsive Polymer Core-Shell Nanoparticles for Drug Delivery.” Unfortunately, this link to the paper doesn’t provide an abstract.

But you’ll find few more details on this page at IBN about “Stimuli-Sensitive Core-Shell Nanoparticles for Cancer Therapy.” [Please note that the URL of this page has been built manually: it's not directly available from the IBN site.]

Conventional chemotherapies for cancer treatment have significant toxic side-effects due to the non-specific absorption of anticancer drugs by all cells. The aim of our project is to develop a smart and safe delivery system to target drugs specifically to tumor cells.

In this project, novel core-shell polymer nanoparticles are designed with their lower critical solution temperature (LCST) being dependent on the ambient pH. This value is above the nominal physiological temperature of 37°C at pH 7.4, but decreases to a temperature below the physiological temperature with a small decrease in pH. The resulting change in LCST causes the core-shell nanoparticles to deform and precipitate in an acidic environment, triggering the release the chemotherapeutics at low pH. In addition, a biological signal has been conjugated to the shell of the nanoparticles, which can recognize tumor cells. This system may be able to target drugs to tumor cells and release the drugs intracellularly.

Finally, the researchers filed a patent application in the U.S. under the name “Nanostructured thermosensitive membranes as wound dressing.”

I can’t give you more details today as the search engine of the United States Patent and Trademark Office (USPTO) seems to be broken, returning internal errors. But try another day: with the name, it should be pretty easy to find it in the USPTO database.

Sources: Institute of Bioengineering and Nanotechnology, March 31, 2005; and various websites

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I’m sure that almost all of you have used a fountain pen. But imagine a pen drawing lines only 40 nanometers in width. Now, it can be done with the Nanofountain Probe (NFP) developed by scientists at Northwestern University. This innovative fountain pen “employs a volcano-like dispensing tip and capillary fed solutions to enable sub-100 nanometer molecular writing.” But it needs to be mounted on an atomic force microscope (AFM) to be useful, so it probably is something you’ll not find at your local drugstore for a while. However, this nanofountain probe could have applications for nanosensors, biotechnology and pharmaceuticals. Read more…

Here is the description of the Nanofountain Probe.

The Nanofountain Probe (NFP) developed by Horacio D. Espinosa, professor of mechanical engineering, and his colleagues employs a volcano-like dispensing tip and capillary fed solutions to enable sub-100 nanometer molecular writing. The NFP was microfabricated on a chip to be mounted on commercially available AFMs.

The device consists of an on-chip reservoir, microchannels and a volcano-like dispensing tip. The microchannels are embedded in the AFM cantilevers of the chip and the volcano dispensing tip has an annular aperture to guide ink dispensing. The ink on the reservoir is driven through the microchannel via capillary action to reach the dispensing tip. At present, the smallest feature width achieved with the device is 40 nanometers.

Below are two images illustrating the technology, with associated comments from the researchers.

High-speed patterning over large areas with the resolution of dip-pen nanolithography (DPN) is the goal of this research by both removing the need for repeated dipping as in the DPN technique and by parallelizing the writing. Our strategy is to combine continuous ink feeding with the DPN technique using micromachining technology.

A novel AFM cantilever integrated with microchannels has been designed and microfabricated. Ink is supplied and stored in an on-chip reservoir, and subsequently fed through the microchannels by capillarity to reach a volcano-shape dispensing tip attached at the end of the cantilever. Batch-fabricated chips can be mounted into commercial atomic force microscopes.

The images above and their legends belong to Espinosa’s Micro & Nanomechanics Laboratory and come from this page about the Nano Fountain Active Probe (NFAP).

But what will be able to do with these probes?

The standard microfabrication techniques used for the NFP chip — an important feature of this development — provides scalability to massively parallel arrays of probes and reservoirs for high throughput patterning with multiple molecular inks.

“The writing capability of such NFP arrays with chemical and bimolecular inks in fountain-pen mode is unique,” said Espinosa. “We believe the technology will likely lead to many high-impact applications in the field of nanosensors, biotechnology and pharmaceuticals.”

The research work has been published by Small, a new scientific journal from the Wiley & Sons group, under the name “A Nanofountain Probe with Sub-100 nm Molecular Writing Resolution.”

Here are two links to the (empty) abstract and to the full paper (PDF format, 4 pages, 176 KB). It also contains other images illustrating the technology.

Here is the conclusion of the paper.

In summary, sub-100 nm molecular patterning has been achieved in fountain-pen writing mode with an AFM probe integrated with a volcano tip, microchannels, and a reservoir. The volcano tip has experimentally shown controlled transport of ink to avoid molecular flooding of substrates, ensuring high-resolution patterning. Standard microfabrication techniques were used, which allow the fabrication of massively parallel fountain probe arrays and integration of multiple reservoirs for sub-100 nm patterning over large areas with multiple inks. The devices have application in the fields of nanolithography, combinatorial nanochemistry, biosensors, nanodevices, and beyond.

Finally, if you want to become a partner of Northwestern University to develop such applications, please check their Technology Transfer Program about the High Speed Nano Fountain Pen.

Sources: Northwestern University news release, April 26, 2005; and various websites

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Using a thin film of silver as the lens and ultraviolet (UV) light, scientists at UC Berkeley have built a superlens able to record images with a resolution of 60 nanometers and suitable for integration in today’s optical microscopes which have only a resolution of down to 400 nanometers. Scanning electron and atomic force microscopes can capture detail down to a few nanometers, but they need minutes to take an image, while this new superlens can take snapshots in a fraction of a second. In the short term, this superlens will lead to new nanoscale biomedical imaging devices. But it also can lead to other advances in nanoengineering such as higher density electronic circuitry or faster fiber optic communications systems. Read more…

Let’s start with a brief description of this achievement.

Using a thin film of silver as the lens and ultraviolet (UV) light, the researchers recorded the images of an array of nanowires and the word “NANO” onto an organic polymer at a resolution of about 60 nanometers. In comparison, current optical microscopes can only make out details down to one-tenth the diameter of a red blood cell, or about 400 nanometers.

At top (A) is the higher resolution image of the word NANO created with a silver superlens. Below that (B) is an image created during a control experiment in which the superlens is replaced by spacer layer. The averaged line width is 60 nanometers in image A with the superlens, and 321 nanometer in image B without the superlens. The scale bar in both images is 2 micrometers. (Image by Cheng Sun, UC Berkeley; legend from UC Berkeley).

Here is a link to a larger version (1,500 x 836 pixels, 214 KB).

[And here are the] detailed procedures of obtaining averaged line cross-section profiles (Color Scale 0-50nm): (A) AFM topography of NANO pattern of the recorded image; (B) Zoom-in AFM image of the letter “A”; (C) A further zoomed-in scan for sufficient digitization of individual lines (in this case each pixel measures 3.9nm) (Credit: UC Berkeley).

Here is what one of the scientists says about this superlens.

“The field of optics is involved in much of today’s technology, including imaging and photolithography, which is used to make semiconductors and integrated circuits,” said Xiang Zhang, UC Berkeley associate professor of mechanical engineering and principal investigator of the study. “Our work has a far reaching impact on the development of detailed biomedical imaging, higher density electronic circuitry and ever-faster fiber optic communications.”

The biggest advantage of optical microscopes equipped with this new superlens over scanning electron and atomic force microscopes is the speed at which it can take images.

“Optical microscopes can capture an entire frame with a single snapshot in a fraction of a second,” said Nicholas Fang, [one of Zhang's former Ph.D. students,] who is now an assistant professor of mechanical engineering at the University of Illinois at Urbana-Champaign.

“That opens up nanoscale imaging to living materials, which can help biologists better understand cell structure and function in real time, and ultimately help in the development of new drugs to treat human diseases.”

Besides using this superlens for optical imaging or high-density optoelectronics, these researchers have also long term visions — or dreams.

In the long run, this line of research could lead to even higher resolution imaging for distant objects, the researchers said. This includes more detailed views of other planets as well as of human movement through surveillance satellites.

Now, let’s go down to Earth.

The research work has been published by Science Magazine on April 22, 2005 under the title “Sub-Diffraction-Limited Optical Imaging with a Silver Superlens” (Vol. 308, Issue 5721, Pages 534-537). Here is a link (free registration required) to the abstract which is reproduced below for your convenience.

Recent theory has predicted a superlens that is capable of producing sub–diffraction-limited images. This superlens would allow the recovery of evanescent waves in an image via the excitation of surface plasmons. Using silver as a natural optical superlens, we demonstrated sub–diffraction-limited imaging with 60-nanometer half-pitch resolution, or one-sixth of the illumination wavelength. By proper design of the working wavelength and the thickness of silver that allows access to a broad spectrum of subwavelength features, we also showed that arbitrary nanostructures can be imaged with good fidelity. The optical superlens promises exciting avenues to nanoscale optical imaging and ultrasmall optoelectronic devices.

Finally, please note that the second image on this page has been extracted from the supporting online material for the article mentioned above (PDF format, 12 pages, 564 KB).

Sources: Sarah Yang, University of California at Berkeley news release, April 21, 2005; Science, Vol. 308, Issue 5721, Pages 534-537, April 22, 2005; and various websites

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Even if researchers are routinely building all kinds of nanodevices in their labs, the current production process of nanowires or nanosensors is similar to the car manufacturing process before Henry Ford. These nanostructures are almost handmade. Now, researchers at University of California Davis (UC Davis) have adapted a technology developed for Hewlett-Packard Laboratories. And they came with two new ways to massively produce nanowires of precise length. Their ‘nanobridges’ and ‘nanocolonnades’ are totally compatible with existing microelectronics fabrication processes. This opens the way for to a wide range of industrial-strength applications, such as bio-chemical sensing, nanoelectronics, nanophotonics, memory and logic devices for future computing. Read more…

First, let’s look at how most nanostructures are produced today.

Nanotechnology, the ability to create and work with structures and materials on an atomic scale, holds the promise of extreme miniaturization for electronics, chemical sensors and medical devices. But while researchers have created tiny silicon wires and connected them together one at a time, these methods cannot easily be scaled up.

“It takes weeks to make one or two, and you end up with different sizes and characteristics,” said M. Saif Islam, assistant professor of electrical and computer engineering, who joined UC Davis from Hewlett-Packard Laboratories in 2004.

Saif Islam and his Integrated Nanodevices and Systems Research (inano) group decided to adapt a technology developed for Hewlett-Packard.

While working at the Quantum Science Research group of Hewlett-Packard Laboratories, Islam and colleagues came up with a new approach. Silicon wafers used for building microcircuits are usually polished at one specific angle to the atomic planes of silicon. Instead, the group used a wafer that was polished at a different angle, changing the orientation of silicon atomic planes to the surface. Using a chemical vapor deposition technique, they could then grow identical, perpendicular columns of silicon.

The researchers have used this method to grow “nanobridges” across a gap between two vertical silicon electrodes. The nanobridges are strong, chemically stable and show better electrical properties than previous approaches, Islam said. They could be used for nanosized transistors, chemical sensors or lasers.

The research work about these ‘nanobridges’ has been published by Applied Physics A, in a special issue on nanotechnology. Here is a link to the abstract of this paper named “A novel interconnection technique for manufacturing nanowire devices” (Volume 80, Number 6, Pages 1133-1140, March 2005).

This paper reviews a novel bridging technique that connects a large number of highly directional metal-catalyzed nanowires between pre-fabricated electrodes and extends the technique to an electrically isolated structure that allows conduction through the nanowires to be measured.

Two opposing vertical and electrically isolated semiconductor surfaces are fabricated using coarse optical lithography, along with wet and dry etching. Lateral nanowires are then grown from one surface by metal-catalyst-assisted chemical vapor deposition; nanowires connect to the other vertical surface during growth, forming mechanically robust nanobridges.

By forming the structure on a silicon-on-insulator substrate, electrical isolation is achieved. Electrical measurements indicate that dopant added during nanowire growth is electrically active and of the same magnitude as in planar epitaxial layers.

Meanwhile, the research about ‘nanocolonnades’ was presented at the spring meeting of the Materials Research Society in San Francisco on April 1, 2005 under the name “Nano-Colonnades: A Novel Technique for Integration of Nanowire Devices.” Here is a link to the program of the symposium where this technology was described.

Finally, I was unable to find any pictures of these ‘nanobridges’ or ‘nanocolonnades.’ If anyone knows about such images, please send me a pointer and I’ll update this entry. Thank you in advance.

Sources: UC Davis News, April 7, 2005; and various websites

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Physicists from several U.S. labs have clocked the transition of vanadium dioxide nanoparticles from a transparent to a reflective, mirror-like state, at less than 100 femtoseconds (a tenth of a trillionth of a second). According to this Vanderbilt University report, this effect has a size limit: “it does not occur in particles that are smaller than about 20 atoms across (10 nanometers).” This opens the door — if I can say so — to windows that are transparent at low temperatures and block out sunlight when the temperature rises. But other applications are possible, such as nanosensors which could measure the temperature at different locations within human cells, or “ultrafast” optical switches which could be used in communications and optical computing. Read more…

Let’s start with an image which probably took lots of work to its creator, René Lopez.

[Note: the transition from visible to non-visible state of Don Quixote and Sancho Panza is viewable (no punt intended!) from the VU article or directly here (Macromedia Flash format).]

Now, let’s go back to the facts as exposed by the Vanderbilt University (VU) online journal.

How this material (vanadium dioxide or VO2) can turn from a transparent insulator into a reflective metal so rapidly has physicists scratching their heads, but a collaboration among researchers at Vanderbilt, Oak Ridge National Laboratory and Lawrence Berkeley National Laboratory has clocked the transfiguration at one-tenth of a trillionth of a second.

“The change from insulator to metal is called a phase transition,” explains Richard Haglund, a Vanderbilt physics professor. “Phase transitions in solids generally occur at the speed of sound in the material, but vanadium dioxide makes the switch 10 times faster. So far no one has succeeded in coming up with a definitive explanation for that rapid a change.”

But now, the researchers think they have one.

The researchers answered that question by detecting the appearance of a phenomenon called “surface plasmon resonance.” This is a form of electron wave that only occurs on the surfaces of metals and is responsible for the glowing colors of stained glass. Detection of this effect confirmed that vanadium dioxide can switch all the way from transparent to reflective in less than 100 femtoseconds (a tenth of a trillionth of a second).

The new Vanderbilt Institute of Nanoscale Science and Engineering (VINSE) allowed these researchers to go further and to discover that this switch effect had some size limits.

This has allowed them to verify that nanoparticles undergo the same phase transition as thin films. They also have determined that the effect has a size limit: It does not occur in particles that are smaller than about 20 atoms across (10 nanometers). The researchers have established that it is possible to raise and lower the temperature at which the insulator/metal transition takes place by as much as 35 degrees Celsius by adding small amounts of impurities.

And this temperature effect leads to new applications.

It is relatively easy to change the material’s transition temperature to body temperature (98 degrees Fahrenheit; 37 degrees Celsius) by adding precise amounts of impurities. Such doped nanoparticles would be small enough to measure the temperature at different locations within an individual cell and, when injected into the body, could pinpoint hot spots by turning into microscopic mirrors.

Of course, there will be other applications for such a fast ‘phase transition’ effect.

For example, they are exploring whether they can create an “ultrafast” optical switch by putting a layer of vanadium dioxide nanoparticles on the end of an optical fiber. Such a switch could be useful in communications and optical computing.

This research work has been explained in a paper published by Optics Letters in its March 2005 issue under the name “Photoinduced phase transition in VO2 nanocrystals: ultrafast control of surface-plasmon resonance” (Volume 30, Issue 5, 558-560). Here is the text of the abstract.

We study the ultrafast insulator-to-metal transition in nanoparticles of VO2, obtained by ion implantation and self-assembly in silica. The nonmagnetic, strongly correlated compound VO2 undergoes a reversible phase transition, which can be photoinduced on an ultrafast time scale. In the nanoparticles, prompt formation of the metallic state results in the appearance of surface-plasmon resonance. We achieve large, ultrafast enhancement of optical absorption in the near-infrared spectral region that encompasses the wavelength range for optical-fiber communications. One can further tailor the response of the nanoparticles by controlling their shape.

Sources: David F. Salisbury, in Exploration, the online journal of Vanderbilt University, April 6, 2005; and various websites

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