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

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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

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At Argonne National Laboratory (ANL), researchers are using new materials to build new and more efficient batteries to put in the vests that will wear next-generation soldiers. For example, the future Army’s Power Vest will use lithium-ion (Li-ion) batteries which will deliver almost twice energy as current Li-ion ones. But Argonne scientists are also developing implantable batteries. These rechargeable batteries, which are 100 times smaller than a standard AA battery, can power implantable microstimulator systems designed to help patients with neurological disorders, such as Parkinson’s disease, or muscular impairments. These batteries are currently under evaluation by industrial partners and should soon be available. Read more…

The ANL news release is almost written in PR lingo, so you’ll find below only short excerpts of it. Let’s start with the body batteries.

Below is a picture of “the world’s smallest cylindrical, rechargeable battery ever made. It is 100 times smaller than a standard AA battery.” (Credit: ANL)

With research partners Quallion LLC and the University of Wisconsin, Argonne developed the battery chemistry for a tiny rechargeable battery — the smallest cylindrical polymer rechargeable battery ever made. The battery is 100 times smaller than a standard AA battery, and powers an implantable microstimulator system designed to help patients with neurological disorders and muscular impairments, such as stroke, Parkinson’s disease and urinary incontinence.

These microstimulator systems would be implanted near nerves, where they emit electrical micropulses that stimulate nearby muscles and nerves. Batteries previously used for medical devices are large, have short lives and are not rechargeable.

Quallion is already selling implantable batteries and here are its I SERIES Specifications.

Now, let’s look at the wearable batteries designed for the Army at ANL’s Chemical Engineering Division known as CMT.

The Army’s Power Vest requires almost double the best energy density currently available and safe, stable operation at varying temperatures. Some of CMT’s patented electrode materials and one of its electrolyte systems are being adapted for the Power Vest.

Compared to conventional materials, Argonne’s new cathode material extends the useable capacity from 150 milliampere-hours per gram to 260. When combined with Argonne’s new process for making spherical dense cathode particles, the combination could provide a 40 percent increase in available energy from the same size battery.

If you’re interested by these developments of new batteries at ANL, you should check this page about their lithium battery technology patents.

Sources: Evelyn Brown, Argonne National Laboratory news release, June 24, 2005; and various web sites

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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

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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

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According to this news release from the National Science Foundation (NSF), American researchers have developed a porous-silicon diode that “convert low levels of radiation into electricity and can have useful lives spanning several decades.” The new ‘BetaBattery’ is more efficient than conventional chemical batteries and potentially cheap to manufacture. It uses a radioactive source as its fuel, the tritium, an hydrogen isotope. When the tritium releases electrons in a process called beta decay, the ‘BetaBattery’ generates electricity by absorbing these electrons. So far, the ‘BetaBattery’ doesn’t deliver as much power as chemical batteries, but it could be extremely useful to power devices which have a long life and are difficult to service, such as structural sensors in bridges and satellites. Read more…

Here is the description of the ‘BetaBattery’ concept.

Using some of the same manufacturing techniques that produce microchips, researchers have created a porous-silicon diode that may lead to improved betavoltaics. Such devices convert low levels of radiation into electricity and can have useful lives spanning several decades.

While producing as little as one-thousandth of the power of conventional chemical batteries, the new “BetaBattery” concept is more efficient and potentially less expensive than similar designs and should be easier to manufacture.

The battery’s staying power is tied to the enduring nature of its fuel, tritium, a hydrogen isotope that releases electrons in a process called beta decay. The porous-silicon semiconductors generate electricity by absorbing the electrons, just as a solar cell generates electricity by absorbing energy from incoming photons of light.

This is not the first time that a radioactive element or even the tritium is used. The real difference of this new device is not its source.

The new cell will have a unique advantage — the half-millimeter-thick silicon wafer into which researchers have etched a network of deep pores. This structure vastly increases the exposed surface area, creating a device that is 10 times more efficient than planar designs.

On the photo below, “Wei Sun of the University of Rochester holds the wafer test fixture the researchers used to test the new porous-silicon diode and its interactions with tritium gas. The diode is the dark wafer in the center of the top plate.” (Credit: University of Rochester; BetaBatt, Inc.)

You can see a larger version of this picture and other images on this page at NSF.

And what will be some applications for these future batteries?

“The initial applications will be for remote or inaccessible sensors and devices where the availability of long-life power is critical,” says Larry Gadeken of BetaBatt, [the only commercial entity involved in this research].

If the new diode proves successful when incorporated into a finished battery, it could help power such hard-to-service, long-life systems as structural sensors on bridges, climate monitoring equipment and satellites.

If you’re interested by the subject, the research work has been published by Advanced Materials on May 3, 2005 (Volume 17, Issue 10, Pages 1230-1233), under the name “A Three-Dimensional Porous Silicon p-n Diode for Betavoltaics and Photovoltaics.” Here is a link to the paper if you’re a registered user (there is no abstract).

And please note that BetaBatt, from Houston, is already selling “a quarter size battery with a 12-20 year lifespan and mission critical reliability” based on its patent number 6,774,531 which carries the name “Apparatus and method for generating electrical current from the nuclear decay process of a radioactive material.”

Sources: National Science Foundation news release, May 10, 2005; and various websites

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As it is often the case, a recent discovery just came out from a simple idea. By studying diseases in which the human body generates too much bone, UCLA researchers have discovered a natural molecule that can be used to generate new bone growth in patients who lack it. This new molecule has aptly been named UCB, or University of California Bone. This new protein for growing bones is more precise and has less side effects than the ones currently used by orthopedic surgeons to aid in bone repair. But if you suffer from a bone deficit today, you’ll have to wait almost ten years before an FDA approval and a commercial introduction of products based on this discovery. Read more…

Here is the beginning of this UCLA news release.

Bioengineering professor Ben Wu at UCLA’s Department of Bioengineering, and Kang Ting, Thomas R. Bales Professor at UCLA’s School of Dentistry, are developing a new molecule they’ve named UCB, or University of California Bone.

[Note: while I was doing my homework research for this entry, I discovered that Kang Ting was sometimes named Eric Ting. I wonder if he prefers to be called Kang or Eric.]

The core technology developed by Wu and Ting is potentially the most significant advancement in bone regeneration since the discovery of bone morphogenetic proteins by Dr. Marshall Urist at UCLA in the 1960s.

“For the average person, this new development potentially means faster, more reliable bone healing with fewer side effects at a lower cost,” Ting said. “In more severe cases, such as in children born with congenital anomalies, the new protein may offer an advanced solution to repair cleft palates, which involves bone deficiencies, and also aid in repairing other bone defects such as fractures, spinal fusion and implant integration.”

Before going further, here is an illustration showing the results of UCB.

On the right part of the image, you can see the bone defect, corrected by the UCB on the left side (Credit: UCLA School of Engineering).

Here is a link to a larger version (1,513 x 517 pixels, 123 KB).

As I mentioned above, UCB is more precise than the bone morphogenetic protein currently used.

With bone morphogenetic proteins, bone formation has been observed to occur at locations outside of the intended implant site, and tissue other than bone also has been reported. In contrast, UCB’s main effects appear to be more specific towards bone formation process, giving surgeons increased control over where bone forms. According to Wu, UCB is more specific because it works downstream from the body’s “master switch” for bone formation.

It’s nice to discover a useful new protein, but how do you move it near the bones when it has to do its work?

The team at UCLA is developing a carrier that is engineered for UCB activities in the biological environment. “It’s the right combination of carrier and protein that further increases the stability and activity of UCB,” Ting said. “For certain clinical applications, we will need to develop injectable options that are minimally invasive. For other clinical applications, we will need moldable carriers that can hold the UCB in place better.”

And when will this molecule be available to patients?

The team of UCLA researchers, under the business name Bone Biologics, already has begun forming partnerships that may assist in the development of appropriate carriers for UCB. Wu and Ting anticipate FDA approval and first sales of the product in the next seven to nine years.

For more information about Bone Biologics, you can read this article from the UCLA Daily Bruin.

Finally, Xinquan Jiang, a visiting scholar from Shanghai, China, and working in Ting’s Lab, won the prestigious 2005 Hatton Award given by the International Association of Dental Research (IADR) for this new technology.

Sources: University of California at Los Angeles news release, April 21, 2005; and various websites

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You certainly know that it’s possible to alter the shape of plastics and polymers by heating them. But now, a team of American and German researchers have found a way to change plastics shape with light, according to this MIT news release. These special polymers can move to new shapes by being exposed to light of specific wavelengths. And they’ll retain this stable new shape until they’re illuminated with another source of light of a different wavelength. This discovery has many potential applications, particularly for medical applications, such as expandable strings keeping blood vessels opened during surgery. Read more…

Here is the introduction of this news release.

Picture a flower that opens when facing the sunlight. In work that mimics that sensitivity to light, an MIT engineer and his German colleagues have created the first plastics that can be deformed and temporarily fixed into shape by light.

Here is how this works.

Key to the work: “molecular switches,” or photosensitive groups that are grafted onto a permanent polymer network. The resulting photosensitive polymer film is then stretched with an external stress and illuminated with ultraviolet light of a certain wavelength. This prompts the molecular switches to crosslink, or bind one to another.

The result? When the light is switched off and the external stress released, the crosslinks remain, maintaining an elongated structure. Exposure to light of another wavelength cleaves the new bonds, allowing the material to spring back to its original shape.

“This is really a new family of materials that can change from one shape to another by having light shined on them,” said Institute Professor Robert Langer of MIT.

And what are some possible applications of these new materials?

Imagine, for example, a “string” of plastic that a doctor could thread into the body through a tiny incision. When activated by light via a fiber-optic probe, that slender string might change into a corkscrew-shaped stent for keeping blood vessels open.

The team is also looking at other medical and industrial applications, such as “paper clips that relax when you don’t need them anymore.”

This research work has been published by Nature in its April 14, 2005 isuue under the title “Light-induced shape-memory polymers.” Here is a link to the abstract and below is the text of this abstract.

Materials are said to show a shape-memory effect if they can be deformed and fixed into a temporary shape, and recover their original, permanent shape only on exposure to an external stimulus. Shape-memory polymers have received increasing attention because of their scientific and technological significance.

In principle, a thermally induced shape-memory effect can be activated by an increase in temperature (also obtained by heating on exposure to an electrical current or light illumination). Several papers have described light-induced changes in the shape of polymers and gels, such as contraction, bending or volume changes. Here we report that polymers containing cinnamic groups can be deformed and fixed into pre-determined shapes — such as (but not exclusively) elongated films and tubes, arches or spirals — by ultraviolet light illumination.

These new shapes are stable for long time periods, even when heated to 50 °C, and they can recover their original shape at ambient temperatures when exposed to ultraviolet light of a different wavelength. The ability of polymers to form different pre-determined temporary shapes and subsequently recover their original shape at ambient temperatures by remote light activation could lead to a variety of potential medical and other applications.

Finally, if the subject interests you, here are two references to previous papers about shape-memory polymers, “Biodegradable, Elastic Shape-Memory Polymers for Potential Biomedical ApplicationsScience” published by Science in May 2002 (free registration for access to the full paper) and “Shape Memory Polymers: Biodegradable Sutures,” published by Materials World in July 2002.

Sources: Elizabeth Thomson, MIT News Office, April 14, 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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Today, we’re using basically two ways to move data in our computers. Transistors carry small amounts of data and are extremely small, while fiber optic cables can carry huge amounts of data, but are much bigger in size. Now, imagine a single technology combining the advantages of photonics and electronics. This Stanford University report says a new technology can do it: plasnomics. (For more about plasmons, read this Wikipedia article.) Theoretically, it is possible to design plasnomic components with the same materials used today by chipmakers, but with frequencies 100,000 times greater than the ones of current microprocessors. There is still a challenge to solve before getting plasnomic chips. Plasmons can only travel a few millimeters before dying while today’s chips are typically about a centimeter across. Read more…

Let’s start with some technical explanations.

Surface plasmons are density waves of electrons — picture bunches of electrons passing a point regularly — along the surface of a metal. Plasmons have the same frequencies and electromagnetic fields as light, but their sub-wavelength size means they take up less space. Plasmonics, then, is the technology of transmitting these light-like waves along nanoscale wires.

“With every wave you can in principle carry information,” says Mark Brongersma, assistant professor of materials science and engineering. [...] “Plasmon waves are interesting because they are at optical frequencies. The higher the frequency of the wave, the more information you can transport.” Optical frequencies are about 100,000 times greater than the frequency of today’s electronic microprocessors.

But let’s get back to the technology.

Plasmons are generated when, under the right conditions, light strikes a metal. The electric field of the light jiggles the electrons in the metal to the light’s frequency, setting off density waves of electrons. The process is analogous to how the vibrations of the larynx jiggle molecules in the air into density waves experienced as sound.

Plasmon waves behave on metals much like light waves behave in glass, meaning that plasmonic engineers can employ all the same ingenious tricks — such as multiplexing, or sending multiple waves — that photonic engineers use to cram more data down a cable.

This sounds good, but is it possible to use this technology today?

Because plasmonic components can be crafted from the same materials chipmakers use today, Stanford engineers are hopeful they can make all the devices needed to route light around a processor or other kind of chip. These would include plasmon sources, detectors and wires, which the lab already has made, as well as splitters and even transistors.

While an all-plasmonic chip might be feasible someday, Brongersma expects that in the near term, plasmonic wires will act as high-traffic freeways on chips with otherwise conventional electronics.

And even Brongersma recognizes that more research needs to be done before getting plasnomic chips.

The potential of plasmonics right now is mainly limited by the fact that plasmons typically can travel only several millimeters before they peter out. Chips, meanwhile, are typically about a centimeter across, so plasmons can’t yet go the whole distance.

The distance a plasmon can travel before dying out is a function of several aspects of the metal. But for optimal transfer through a wire of any metal, the surface of contact with surrounding materials must be as smooth as possible and the metal should not have impurities.

For more information, you can check the following resources.

• “Plasmonic computer chips move closer,” an article published by New Scientist on March 17, 2005
  
  
• The Brongersma Group website and its current research projects
  
  
• The abstract of a presentation given on May 21, 2005 at the March 2005 Meeting of the American Physical Society, “Sub-wavelength confinement and the diffraction limit for surface plasmon waveguides”
  

Sources: David Orenstein, Stanford University Report, March 16, 2005; and various websites

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In “Wearable Computers You Can Slip Into,” BusinessWeek Online reviews several new unobtrusive wearable devices, such as a handbag with embedded chips. When this bag becomes available for about $150 in two or three years, it will remind you to grab your wallet or to pick an umbrella before going out. And according to research firm IDC, the clunky wearable computers which required users to be wrapped in wires like Christmas gifts are quickly becoming things of the past. The future of wearable computers is already here, especially for some health-care applications, such as a ’smart band’ that collects data on your physical activities and can be used as a weight-loss monitoring tool. But read more…

Let’s start with a bag designed by Gauri Nanda and fellow researchers at the MIT.

Gauri Nanda sees a wearable computer as a… handbag — one that’s built out of four-inch squares and triangles of fabric, with tiny computer chips embedded in it. Assembled together with Velcro that conducts electricity, these pieces form a bag that looks, feels, and weighs like your typical leather purse.

That’s where the similarities end: This bag can wirelessly keep tabs on your belongings and remind you, just as you’re about to leave the house, to take your wallet. It can review the weather report and suggest that you grab an umbrella — or your sunshades. This purse can even upload your favorite songs onto your scarf.

Of course, this kind of bag is using new technologies, such as RFID tags embedded in your wallet, or special fabrics, such as the Aracon fiber from DuPont. But the surprising thing is that — no pun intended — it will not break your wallet. Such a bag will cost only about $150.

Now, here is the ’smart band’ from BodyMedia, which is about to be deployed in fitness clubs.

Here, you can see how this works in the above image (Credit: BodyMedia). The unobtrusive ’smart band’ collects data on your physical activity, which is then processed by proprietary algorithms and finally displayed on a variety of devices.

Originally released three years ago as a tool for researchers — auto makers, for example, used it to understand stress in drivers — the band is about to enter the mainstream. Later this month, Apex Fitness Group, which distributes fitness products to 1,200 health clubs such as 24-hour Fitness, will begin promoting the band for consumers as a weight-loss monitoring tool [and under a cute trademarked name -- bodybugg.]

Then, there is a special shirt developed by VivoMetrics to monitor patients at hospitals, and which can also be used to accelerate new treatment trials.

Because of the volume of data it collects, the shirt can significantly reduce the number of participants in trials, as well as the trials’ duration. In the case of one study for a sleep drug, traditional methods like hooking up patients to various machines at a special sleep lab “would have been at least 10 times more expensive and would have taken 10 times longer,” says Steven James, a San Diego consultant to pharmaceutical companies. During this trial, 15 patients simply wore the shirts at home overnight. VivoMetrics sells a set of six shirts and related software and data recorders for $15,000.

Finally, BusinessWeek Online reports about the Nomad head-mounted display from Microvision, Inc. You can find more information about this device in a previous post from December 2004, “New Wearable Armyware.”

Sources: Olga Kharif, BusinessWeek Online, March 8, 2005; and various websites

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Today, we’ll look at nanotechnology under an unusual angle: the impact on the jewelry industry. In this long article, “The Weird World of Precious Metal Nanotechnology,” published by AJM Magazine (The Authority on Jewelry Manufacturing), Michael Cortie, professor at the University of Sydney, Australia, explains why gold is often used by nanotechnologists. Not only gold exhibits very interesting properties at the nanoscale level, but it’s also a bargain when compared to current prices of carbon nanotubes. And gold — and silver — nanoparticles can offer a range of unusual colors, suitable for fine jewelry or luxurious coatings. Finally, Cortie envisions smart jewelry made possible through the use of nanotechnology, such as a pendant that could include cell phone capabilities.

Please read the whole article for many more details about the birth of nanotechnology and let’s jump to the section explaining why gold is so often used by nanotechnologists. Here are two important paragraphs.

Thousands of technologists have independently arrived at this conclusion. As a result, gold particles, wires, and surfaces are at the heart of much of nanotechnology. At this scale, the inherent softness of pure gold is not an issue, nor is its high intrinsic value. In addition to resistance to corrosion, gold’s electrical conductivity and special affinity for sulfur-containing organic molecules are also particularly attractive features. These properties allow chemists to design molecules that can stick onto the gold in a controlled fashion, and then be probed by electrical currents. This permits the bottom-up assembly of quite interesting and promising structures, such as ultra-sensitive biosensors.

It is important to note that the relatively high value of gold is not expected to impede its penetration into the high tech markets. The value of the tiny amounts of gold used in existing or anticipated nanotech products is completely swamped by the overall added value of the product. Manufacturers will use gold when it provides the best technological performance, and they will not be overly concerned by its price. A $20 medical test kit or sensor might contain gold worth only 50 cents, yet it may be this critical ingredient that makes the whole device possible. In any case, gold is far cheaper than the highly touted carbon nanotube, the other material frequently associated with nanotechnology. Single-wall carbon nanotubes cost $400 per gram when in reasonable purity. The cost increases to $1,500 per gram or $46,000 per troy ounce for highly processed carbon nanotubes. Gold is a bargain compared to this.

Now, it’s time to look at the unusual colors exhibited by gold nanoparticles.

After the images, here is an explanation.

One of the features of gold and silver nanoparticles is that they possess a range of quite unusual colors. Bulk gold has a familiar yellow color, which is caused by a reduction in the reflectivity of light at the blue end of the spectrum. However, if we subdivide the gold into smaller and smaller particles, there comes a point at which the particle size becomes smaller than the wavelength of incident light. New modes of interaction between the radiation and the gold become prominent, in particular interactions involving electronic oscillations called surface plasmons. When the particles of gold are small enough, they are ruby red in color. This coloration is due to the gold particles’ strong absorption of green light, corresponding to the frequency at which a resonance occurs with the gold.

Will these unusual colors be used for real jewels one day?

The jury is still out on this question. Certainly, to be of value in fine jewelry, the karatage of the colored gold should be high. This probably excludes many of the commonly prepared colored glasses as possible materials from which to produce a piece of jewelry. But it is worth noting that, in theory, interesting colors are possible up to about 23 karats. This is because of the high density of gold relative to the various candidate transparent matrix materials. The trick will be to find a matrix to hold the precious metal nanoparticles. However, the availability of gold gilding pastes and paints of very high metal content shows that there is no theoretical limitation that prevents this possibility.

Finally, Cortie looks at a future where we could carry ’smart’ jewels.

Will there be a general trend toward integrating some technological devices into items of jewelry? It is certainly becoming possible. Candidate functionalities include bracelets that could record their owner’s blood pressure and heartbeat, or a pendant that could include cell phone capabilities. There are problems of hallmarking, of course, and no doubt many would see such items as tawdry. However, a small market already exists for color-change and other novelty jewelry, so it is possible, for example, that an integration of electronic “smarts” with a gold nanoparticle color change functionality might appeal to some markets.

For more information, an extended — and more technical — version of Cortie’s work has been published in June 2004 by Gold Bulletin under the title “The Weird World of Nanoscale Gold” (PDF format, 8 pages with diagrams, 120 KB).

Source: Michael Cortie, for AJM Magazine (The Authority on Jewelry Manufacturing), March 2005

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If you enjoy fishing, I have some good news for you. According to New Scientist in “Light-emitting line reels in the big fish,” American chemists have designed a blend of polymers which changes color if it has been exposed to a previous excessive stress. Before going to fight with a 300-pound marlin, you’ll have to put your fishing line under ultraviolet light. If some parts of the line appear green, it should break soon, so it’s time to switch to a new one before jumping in your boat. But these new fishing lines will not be on sale for a while. First, the changes of colors should be visible under normal light conditions, not only under UV. And real fishing lines are much stronger than the ones fabricated today in the lab. Read more…

Here is the somewhat ‘teasing’ introduction from the New Scientist article.

The big ones might not get away quite so often if an experimental fishing line finds its way to market. The new line changes colour when it has been subjected to too much stress, warning the angler that it is in danger of breaking.

Nylon fishing line is designed to have some stretch. But pull on it too hard — when fighting a large fish, for example, or trying to get loose from a snag — and it can reach the point of “non-recoverable deformation” at which it becomes seriously weakened.

So how did the chemists solve this problem?

The new line has been developed by Christoph Weder, Brent Crenshaw and Jill Kunzelman at Case Western Reserve University in Cleveland, Ohio, US. It contains a type of polymer called a phenylene vinylene oligomer, which fluoresces under ultraviolet light. Crucially, the colour of the light it gives off changes depending on the mechanical stress the molecule has been subjected to.

To make the fishing line, a small amount of the polymer is mixed into standard low-density polyethylene, making up 0.2% of the blend. When the line is not under stress, the polymer molecules are close together and emit reddish-brown visible light when illuminated by UV radiation. But when the material stretches and the polymer molecules pull apart, they fluoresce green. So an angler who feared that a section of line had been under excessive stress could examine it under UV light, and discard it if it glowed green.

As I said above, there are still some hurdles to overcome before you could buy these fishing lines at your local fishing store.

Even more useful would be a polymer whose colour change is visible in normal light, says Crenshaw, who is a graduate student at Case Western’s Functional Polymer Laboratory. He says the team is evaluating possible materials.

The polyethylene fishing line is for demonstration only: it would not be strong enough to stand up to even a 4-kilogram bass, Crenshaw says. But there is no reason the same could not be done with standard nylon fishing line.

For more information, please check the Functional Polymers group site at Case Western Reserve University, and in particular this page about functional polymer blends, where the researchers describe their projects.

Rather than designing and synthesizing new, complex functional macromolecules, minor fractions of a “functional additive” are blended with an “inert matrix polymer” in order to create (often after rather specific processing protocols) a new material with a unique or unusual property matrix.

One key project is focused on the design, synthesis, processing, and characterization of polymer materials with integrated mechanical deformation sensors. Materials with self-assessing capabilities are being investigated, in which photoluminescence is employed as the general sensing principle. The approach is based on the incorporation of small amounts of fluorescent dyes into conventional polymers and relies on the formation of nanoscale aggregates of these sensor molecules in the polymer matrix.

The equilibrium phase behavior of these systems can be influenced via the dye’s chemical structure and the material’s composition. The kinetic aspects of aggregate formation can primarily be manipulated via the processing protocol. Therefore the supramolecular architecture of the targeted polymer/dye nanocomposites can be very well controlled. The approach further exploits that mechanical deformation of these materials leads to shear-induced mixing, which transforms the nanophase-separated systems into molecular mixtures.

As you can see, fishing is not really a major concern for these researchers.

Sources: Kurt Kleiner, New Scientist, February 12, 2005; and various pages at Case Western Reserve University

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Many teams of nanoscientists around the world want to be the first one to build quantum computers. To achieve this goal, they’re using artificial atoms — also known as ‘quantum dots.’ But even if they’re able to use them, not a single team has been able to consistently control their quantum mechanical states — or their properties — at the nanoscale. Now, a team from Ohio University claims it found a flaw in quantum dot construction and proposes a solution. And guess what? As it happens often in research, this new finding is based on a very simple fact: an interference between two physical phenomena. Read more…

[For example,] experimental scientists in Germany had blasted the quantum dots with light to create the quantum mechanical state needed to run a quantum computer. But they couldn’t consistently control that state, explained Sergio Ulloa, an Ohio University professor of physics and astronomy. Jose Villas-Boas, a postdoctoral fellow at Ohio University, Ulloa and Associate Professor Alexander Govorov developed theoretical models to learn what went wrong.

The problem, they argued, happens during the creation of the type of quantum dots under study. Using a molecular beam epitaxy chamber, scientists spray paint a surface with atoms under high temperatures, creating an atomic coating. As more layers are added, the quantum dots bead up on the surface like droplets of water, Ulloa said.

But a fine residue left behind on the surface that Ulloa calls the “wetting layer” can cause problems during experiments. When experimental scientists blasted the quantum dots with a beam of light in previous studies, the wetting layer caused interference, instead of allowing the light to enter the dot and trigger the quantum state, he explained.

The illustration above “shows a quantum dot (blue central bulge) bombarded from the top with laser light. The laser produces excitations (called excitons) inside the dot, and the electric fields generated by the top and bottom gold contacts pull the electrons (yellow) and holes (red) away. Other electrons/holes are undesirably produced instead on the wetting layer, causing interference. The semiconductor compounds used in these experiments are Gallium Arsenide (GaAs) and Indium Gallium Arsenide (InGaAs).” (Credit for image and legend: Jose Villas-Boas) Here is a link to a larger version.

The study suggests that scientists could tweak the process by re-focusing the beam of light or changing the duration of the light pulses to negate the effects of the wetting layer, Villas-Boas said. One experimental physicist already has used the theoretical finding to successfully manipulate a quantum dot in the lab, he added. “Now that they know the problem, they realize there are a few ways to avoid it,” Villas-Boas said.

The research work from these scientists at the Ohio University’s Nanoscale & Quantum Phenomena Institute has been published in a recent issue of Physical Review Letters on February 8, 2005 under the name “Decoherence of Rabi Oscillations in a Single Quantum Dot.” Here is a link to the abstract.

We develop a realistic model of Rabi oscillations in a quantum-dot photodiode. Based in a multiexciton density matrix formulation we show that for short pulses the two-level model fails and higher levels should be taken into account. This affects some of the experimental conclusions, such as the inferred efficiency of the state rotation (population inversion) and the deduced value of the dipole interaction. We also show that the damping observed cannot be explained using constant rates with fixed pulse duration. We demonstrate that the damping observed is in fact induced by an off-resonant excitation to or from the continuum of wetting layer states. Our model describes the nonlinear decoherence behavior observed in recent experiments.

And if you want to know more, but don’t want to buy the article, here is a link to the full article (PDF format, 5 pages, 221 KB), thanks to the invaluable arXiv.org website.

Finally, just in case you wouldn’t know anything about Rabi oscillations, please read Isidor Isaac Rabi’s biography. He won the Nobel Prize for Physics in 1944.

Sources: Andrea Gibson, Ohio University, via EurekAlert!, February 10, 2005; and various websites

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Once again, I’m amazed by the creativity of scientists. Researchers at Cornell University have made a brilliant and environmentally friendly discovery: plastics made from orange peel and a greenhouse gas. By adding a zinc catalyst to a mix of citrus fruits, such as oranges, and carbon dioxide, they found a way to make a new polymer called polylimonene carbonate, very similar to polystyrene, a petroleum-based plastic. This is a double whammy: it will reduce existing carbon dioxide, almost certainly responsible for the global warming effect, while reducing future emissions. Of course, time will pass between this discovery and its practical applications. But ultimately, this will greatly beneficial to all of us. Read more…

A Cornell University research group has made a sweet and environmentally beneficial discovery — how to make plastics from citrus fruits, such as oranges, [which contain limonene oxide ]and carbon dioxide.

Limonene is a carbon-based compound produced in more than 300 plant species. In oranges it makes up about 95 percent of the oil in the peel.

In industry, explains Geoffrey Coates, a Cornell professor of chemistry and chemical biology, the orange peel oil is extracted for various uses, such as giving household cleaners their citrus scent. The oil can be oxidized to create limonene oxide. This is the reactive compound that Coates and his collaborators used as a building block.

The other building block they used was carbon dioxide (CO₂), an atmospheric gas that has been rising steadily over the past century and a half — due largely to the combustion of fossil fuels — becoming an environmentally harmful greenhouse gas.

By using their catalyst to combine the limonene oxide and CO₂, the Coates group produced a novel polymer — called polylimonene carbonate — that has many of the characteristics of polystyrene, a petroleum-based plastic currently used to make many disposable plastic products.

The above diagram shows the very simple process of making polymers by adding a catalyst to a mix of limonene oxide and carbon dioxide (Credit: Cornell University)

And here is Coates’s conclusion.

“Almost every plastic out there, from the polyester in clothing to the plastics used for food packaging and electronics, goes back to the use of petroleum as a building block,” Coates observes. “If you can get away from using oil and instead use readily abundant, renewable and cheap resources, then that’s something we need to investigate. What’s exciting about this work is that from completely renewable resources, we were able to make a plastic with very nice qualities.”

The research work has been published by the Journal of the American Chemical Society (Vol. 126, No. 37, September 22, 2004, Pages 11404-11405, Link).

Here is a direct link to the abstract of this paper called “Alternating Copolymerization of Limonene Oxide and Carbon Dioxide.”

For more information, you can check these pages about Geoffrey Coates and his research group.

Here is what Coates says about his research on polymers created from renewable resources, and more specifically about the copolymerization of CO₂ and epoxides.

Carbon dioxide is an ideal synthetic feedstock since it is abundant, inexpensive, nontoxic, and nonflammable. Although it is estimated that Nature uses CO₂ to make over 200 billion tons of glucose by photosynthesis each year, synthetic chemists have had embarrassing little success in developing efficient catalytic processes that exploit this attractive raw material. There has been considerable recent interest in the development of catalysts for the alternating copolymerization of carbon dioxide with epoxides to produce aliphatic polycarbonates. Due to the low cost and accessibility of the monomers and the attractive properties of polycarbonates, the development of new, efficient initiators for this polymerization process is a significant scientific goal. We have recently discovered a new class of well-defined, highly active zinc-based catalysts that copolymerize carbon dioxide and epoxides under exceptionally mild conditions. These catalysts are remarkable since they are several orders of magnitude more active than the current commercial catalysts.

Let’s hope that this discovery quickly leaves the lab…

Sources: Sarah Davidson, Cornell University news release, January 17, 2005; and various websites

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