New 'Electronic Glue' Promises Less Expensive Semiconductors

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ScienceDaily (June 24, 2009) — Researchers at the University of Chicago and Lawrence Berkeley National Laboratory have developed an "electronic glue" that could accelerate advances in semiconductor-based technologies, including solar cells and thermoelectric devices that convert sun light and waste heat, respectively, into useful electrical energy.

Semiconductors have served as choice materials for many electronic and optical devices because of their physical properties. Commercial solar cells, computer chips and other semiconductor technologies typically use large semiconductor crystals. But that is expensive and can make large-scale applications such as rooftop solar-energy collectors prohibitive.
For those uses, engineers see great potential in semiconductor nanocrystals, sometimes just a few hundred atoms each. Nanocrystals can be readily mass-produced and used for device manufacturing via inkjet printing and other solution-based processes. But a problem remains: The crystals are unable to efficiently transfer their electric charges to one another due to surface ligands—bulky, insulating organic molecules that cap nanocrystals.
The "electronic glue" developed in Dmitri Talapin's laboratory at the University of Chicago solves the ligand problem. The team describes in the journal Science how substituting the insulating organic molecules with novel inorganic molecules dramatically increases the electronic coupling between nanocrystals. The University of Chicago licensed the underlying technology for thermoelectric applications to Evident Technologies in February.
Journal reference:
Maksym V. Kovalendo et al. Colloidal Nanocrystals with Molecular Metal Chalcogenide Surface Ligands. Science, June 12, 2009
Adapted from materials provided by University of Chicago, via EurekAlert!, a service of AAAS.

Autonomous Robot Detects Shrapnel In Flesh

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ScienceDaily (June 24, 2009) — Bioengineers at Duke University have developed a laboratory robot that can successfully locate tiny pieces of metal within flesh and guide a needle to its exact location -– all without the need for human assistance.

The successful proof-of-feasibility experiments lead the researchers to believe that in the future, such a robot could not only help treat shrapnel injuries on the battlefield, but might also be used for such medical procedures as placing and removing radioactive "seeds" used in the treatment of prostate and other cancers.
In their latest experiments, the engineers started with a rudimentary tabletop robot whose "eyes" are a novel 3-D ultrasound technology developed at Duke. An artificial intelligence program served as the robot's "brain" by taking the real-time 3-D information, processing it and giving the robot specific commands to perform. In their simulations, the researchers used tiny (2 millimeter) pieces of needle because, like shrapnel, they are subject to magnetism.
"We attached an electromagnet to our 3-D probe, which caused the shrapnel to vibrate just enough that its motion could be detected," said A.J. Rogers, who just completed an undergraduate degree in bioengineering at Duke. "Once the shrapnel's coordinates were established by the computer, it successfully guided a needle to the site of the shrapnel."
By proving that the robot could guide a needle to an exact location, it would simply be a matter of replacing the needle probe with a tiny tool, such as a grabber, the researchers said.
Rogers worked in the laboratory of Stephen Smith, director of the Duke University Ultrasound Transducer Group and senior member of the research team. The results of the experiments were published early online in the July issue of the journal IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.
Since the researchers achieved positive results using a rudimentary robot and a basic artificial intelligence program, they are encouraged that simple and reasonably safe procedures will become routine in the near future as robot and artificial intelligence technology improves.
"We showed that in principle, the system works," Smith said. "It can be very difficult using conventional means to detect small pieces of shrapnel, especially in the field. The military has an extensive program of exploring the use of surgical robots in the field, and this advance could play a role."
In addition to its applications recovering the radioactive seeds used in treating prostate cancer, Smith said the system could also prove useful in removing foreign, metallic objects from the eye.
Advances in ultrasound technology have made these latest experiments possible, the researchers said, by generating detailed, 3-D moving images in real-time. The Duke team has a long track record of modifying traditional 2-D ultrasound – like that used to image babies in utero – into the more advanced 3-D scans. Since inventing the technique in 1991, the team has shown its utility by developing specialized catheters and endoscopes for real-time imaging of blood vessels in the heart and brain.
In the latest experiments, the robot successfully performed its main task: locating a tiny piece of metal in a water bath, then directing a needle on the end of the robotic arm to it. The researchers had previously used this approach to detect micro-calcifications in simulated breast tissue. In the latest experiments, Rogers added an electromagnet to the end of the transducer, or wand, the device that sends out and receives the ultrasonic waves.
"The movement caused by the electromagnet on the shrapnel was not visible to the human eye," Rogers said. "However, on the 3-D color Doppler system, the moving shrapnel stood out plainly as bright red."
The robot used in these experiments is a tabletop version capable of moving in three axes. For the next series of tests, the Duke researchers plan to use a robotic arm with six-axis capability.
The research in Smith's lab is supported by the National Institutes of Health. Duke's Ned Light was also part of the research team.
Adapted from materials provided by Duke University. Original article written by Richard Merritt.

Making Nanoparticles In Artificial Cells

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ScienceDaily (June 27, 2009) — Two new construction manuals are now available for the world's smallest lamps. Based on these protocols, scientists from the Max Planck Institute of Colloids and Interfaces have tailor-made nanoparticles that can be used as position lights on cell proteins and, possibly in the future as well, as light sources for display screens or for optical information technology.

The researchers produced cadmium sulphide particles in microscopically small membrane bubbles. Depending on which of the construction manuals they follow, the particles can be 4 or 50 nanometres in size. Because the membrane bubbles have the same size as living cells, the scientists' work also provides an indication as to how nanostructures could arise in nature.
Cells and microorganisms are absolute masters when it comes to working in the smallest possible dimensions. Like particularly efficient micro-factories, they produce particles and structures from inorganic material, for example pieces of chalk, that are only a few nanometres in size, that is, millionths of a millimetre. Cells have two different factors to thank for this capability. First, they have peptides, a biological tool at their disposal that may shape the chalk into a desired form. Second, the fact that they are very small themselves is convenient: the chalk particles cannot grow boundlessly - the end is reached when the calcium carbonate, the building block of chalk, runs out in the cell.
"We used the fact that cells represent a closed reaction container as a model for the synthesis of nanoparticles," says Rumiana Dimova. Her group at the Max Planck Institute of Colloids and Interfaces studies membranes - the cell envelope. The scientist and her colleagues form bubbles that are around 50 micrometres in size from lecithin membranes, which are similar to biological membranes. Like cells, membrane bubbles - or vesicles as scientists refer to them - also provide a closed reaction container. The scientists load the membrane bubbles with one of two reactants for the nanoparticles.
From this point, the researchers have developed two different sets of protocols. In one case, they produce bubbles loaded with one of the two reactants, sodium sulphide or cadmium chloride. The scientists then bring the bubbles with the different loads together and fuse two vesicles to form a bigger vesicle - this is done by subjecting the bubble cocktail to a short but very strong electrical pulse. The electric shock fuses the membranes of two adjacent bubbles.
In many cases, this results in the fusion of two bubbles containing different reactants. These then react to form cadmium sulphide, which is not water soluble and thus precipitates in the form of nanoparticles. "Because the reactants are only present to a limited extent in the fused bubbles, the particles only grow to a size of four nanometres," explains Rumiana Dimova. The scientists were able to track the entire process directly under the microscope because they had added different fluorescent molecules to the membranes of the differently loaded vesicles. The researchers were also able to see the nanoparticles forming as the particles shone like tiny lamps.
In the second process, the researchers only produce vesicles with one of the reactants. When the vesicles have formed, unlike in the first procedure, the researchers do not remove them from the production chamber. Instead, the bubbles remain attached to their substrate via small membrane channels, like balloons tied to strings, and stand in a solution that is the same as the one inside them. The researchers working with Rumiana Dimova then altered this situation: they substituted the solution with the first ingredient for the nanoparticles with a second component. This causes no change inside the vesicles at first. The second ingredient only creeps gradually between the substrate and membrane into the channel and to the vesicle. In the vesicle, where the other ingredient is already waiting, the nanoparticles grow again - this time to a size of 50 nanometres.
"With our method, we succeeded for the first time in producing particles with a certain diameter in vesicles whose size corresponds to that of cells," says Rumiana Dimova. Previously, biologists thought that cells depended on the help of peptides for the synthesis of nanoparticles. However, as Rumiana Dimova and her colleagues have discovered, it can also be done without them.
Journal reference:
Yang et al. Nanoparticle Formation in Giant Vesicles: Synthesis in Biomimetic Compartments. Small, 2009; DOI: 10.1002/smll.200900560
Adapted from materials provided by Max-Planck-Gesellschaft.

First Acoustic Metamaterial 'Superlens' Created.

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ScienceDaily (June 25, 2009) — A team of researchers at the University of Illinois has created the world’s first acoustic “superlens,” an innovation that could have practical implications for high-resolution ultrasound imaging, non-destructive structural testing of buildings and bridges, and novel underwater stealth technology.

The team, led by Nicholas X. Fang, a professor of mechanical science and engineering at Illinois, successfully focused ultrasound waves through a flat metamaterial lens on a spot roughly half the width of a wavelength at 60.5 kHz using a network of fluid-filled Helmholtz resonators.
According to the results, published in the May 15 issue of the journal Physical Review Letters, the acoustic system is analogous to an inductor-capacitor circuit. The transmission channels act as a series of inductors, and the Helmholtz resonators, which Fang describes as cavities that house resonating waves and oscillate at certain sonic frequencies almost as a musical instrument would, act as capacitors.
Fang said acoustic imaging is somewhat analogous to optical imaging in that bending sound is similar to bending light. But compared with optical and X-ray imaging, creating an image from sound is “a lot safer, which is why we use sonography on pregnant women,” said Shu Zhang, a U. of I. graduate student who along with Leilei Yin, a microscopist at the Beckman Institute, are co-authors of the paper.
Although safer, the resultant image resolution of acoustic imaging is still not as sharp or accurate as conventional optical imaging.
“With acoustic imaging, you can’t see anything that’s smaller than a few millimeters,” said Fang, who also is a researcher at the institute. “The image resolution is getting better and better, but it’s still not as convenient or accurate as optical imaging.”
The best tool for tumor detection is still the optical imaging, but exposure to certain types of electromagnetic radiation such as X-rays also has its health risks, Fang noted.
“If we wish to detect or screen early stage tumors in the human body using acoustic imaging, then better resolution and higher contrast are equally important,” he said. “In the body, tumors are often surrounded by hard tissues with high contrast, so you can’t see them clearly, and acoustic imaging may provide more details than optical imaging methods.”
Fang said that the application of acoustic imaging technology goes beyond medicine. Eventually, the technology could lead to “a completely new suite of data that previously wasn’t available to us using just natural materials,” he said.
In the field of non-destructive testing, the structural soundness of a building or a bridge could be checked for hairline cracks with acoustic imaging, as could other deeply embedded flaws invisible to the eye or unable to be detected by optical imaging.
“Acoustic imaging is a different means of detecting and probing things, beyond optical imaging,” Fang said.
Fang said acoustic imaging could also lead to better underwater stealth technology, possibly even an “acoustic cloak” that would act as camouflage for submarines. “Right now, the goal is to bring this ‘lab science’ out of the lab and create a practical device or system that will allow us to use acoustic imaging in a variety of situations,” Fang said.
Funding for this research was provided by the Defense Advanced Research Projects Agency, the central research and development agency for the U.S. Department of Defense.
Adapted from materials provided by University of Illinois at Urbana-Champaign.

Living Safely with Robots, Beyond Asimov's Laws

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TOPIO 2.0 - TOSY Ping Pong Playing Robot version 2 at Nuremberg International Toy Fair 2009. Image: Wikimedia Commons.

(PhysOrg.com) -- "In 1981, a 37-year-old factory worker named Kenji Urada entered a restricted safety zone at a Kawasaki manufacturing plant to perform some maintenance on a robot. In his haste, he failed to completely turn it off. The robot’s powerful hydraulic arm pushed the engineer into some adjacent machinery, thus making Urada the first recorded victim to die at the hands of a robot."

In situations like this one, as described in a recent study published in the International Journal of Social Robotics, most people would not consider the accident to be the fault of the robot. But as robots are beginning to spread from industrial environments to the real world, human safety in the presence of robots has become an important social and technological issue. Currently, countries like Japan and South Korea are preparing for the “human-robot coexistence society,” which is predicted to emerge before 2030; South Korea predicts that every home in its country will include a robot by 2020. Unlike industrial robots that toil in structured settings performing repetitive tasks, these “Next Generation Robots” will have relative autonomy, working in ambiguous human-centered environments, such as nursing homes and offices. Before hordes of these robots hit the ground running, regulators are trying to figure out how to address the safety and legal issues that are expected to occur when an entity that is definitely not human but more than machine begins to infiltrate our everyday lives.
In their study, authors Yueh-Hsuan Weng, a Kyoto Consortium for Japanese Studies (KCJS) visiting student at Yoshida, Kyoto City, Japan, along with Chien-Hsun Chen and Chuen-Tsai Sun, both of the National Chiao Tung University in Hsinchu, Taiwan, have proposed a framework for a legal system focused on Next Generation Robot safety issues. Their goal is to help ensure safer robot design through “safety intelligence” and provide a method for dealing with accidents when they do inevitably occur. The authors have also analyzed Isaac Asimov’s Three Laws of Robotics, but (like most robotics specialists today) they doubt that the laws could provide an adequate foundation for ensuring that robots perform their work safely.
One guiding principle of the proposed framework is categorizing robots as “third existence” entities, since Next Generation Robots are considered to be neither living/biological (first existence) or non-living/non-biological (second existence). A third existence entity will resemble living things in appearance and behavior, but will not be self-aware. While robots are currently legally classified as second existence (human property), the authors believe that a third existence classification would simplify dealing with accidents in terms of responsibility distribution.
One important challenge involved in integrating robots into human society deals with “open texture risk” - risk occurring from unpredictable interactions in unstructured environments. An example of open texture risk is getting robots to understand the nuances of natural (human) language. While every word in natural language has a core definition, the open texture character of language allows for interpretations that vary due to outside factors. As part of their safety intelligence concept, the authors have proposed a “legal machine language,” in which ethics are embedded into robots through code, which is designed to resolve issues associated with open texture risk - something which Asimov’s Three Laws cannot specifically address.
“During the past 2,000 years of legal history, we humans have used human legal language to communicate in legal affairs,” Weng told PhysOrg.com. “The rules and codes are made by natural language (for example, English, Chinese, Japanese, French, etc.). When Asimov invented the notion of the Three Laws of Robotics, it was easy for him to apply the human legal language into his sci-fi plots directly.”
As Chen added, Asimov’s Three Laws were originally made for literary purposes, but the ambiguity in the laws makes the responsibilities of robots’ developers, robots’ owners, and governments unclear.
“The legal machine language framework stands on legal and engineering perspectives of safety issues, which we face in the near future, by combining two basic ideas: ‘Code is Law’ and ‘Embedded Ethics,’” Chen said. “In this framework, the safety issues are not only based on the autonomous intelligence of robots as it is in Asimov’s Three Laws. Rather, the safety issues are divided into different levels with individual properties and approaches, such as the embedded safety intelligence of robots, the manners of operation between robots and humans, and the legal regulations to control the usage and the code of robots. Therefore, the safety issues of robots could be solved step by step in this framework in the future.”
Weng also noted that, by preventing robots from understanding human language, legal machine language could help maintain a distance between humans and robots in general.
“If robots could interpret human legal language exactly someday, should we consider giving them a legal status and rights?” he said. “Should the human legal system change into a human-robot legal system? There might be a robot lawyer, robot judge working with a human lawyer, or a human judge to deal with the lawsuits happening inter-human-robot. Robots might learn the kindness of humans, but they also might learn deceit, hypocrisy, and greed from humans. There are too many problems waiting for us; therefore we must consider if it is a better to let the robots keep a distance from the human legal system and not be too close to humans.”
In addition to using machine language to keep a distance between humans and robots, the researchers also consider limiting the abilities of robots in general. Another part of the authors’ proposal concerns “human-based intelligence robots,” which are robots with higher cognitive abilities that allow for abstract thought and for new ways of looking at one’s environment. However, since a universally accepted definition of human intelligence does not yet exist, there is little agreement on a definition for human-based intelligence. Nevertheless, most robotics researchers predict that human-based intelligence will inevitably become a reality following breakthroughs in computational artificial intelligence (in which robots learn and adapt to their environments in the absence of explicitly programmed rules). However, a growing number of researchers - as well as the authors of the current study - are leaning toward prohibiting human-based intelligence due to the potential problems and lack of need; after all, the original goal of robotics was to invent useful tools for human use, not to design pseudo-humans.
In their study, the authors also highlight previous attempts to prepare for a human-robot coexistence society. For example, the European Robotics Research Network (EURON) is a private organization whose activities include investigating robot ethics, such as with its Roboethics Roadmap. The South Korean government has developed a Robot Ethics Charter, which serves as the world’s first official set of ethical guidelines for robots, including protecting them from human abuse. Similarly, the Japanese government investigates safety issues with its Robot Policy Committee. In 2003, Japan also established the Robot Development Empiricism Area, a “robot city” designed to allow researchers to test how robots act in realistic environments.
Despite these investigations into robot safety, regulators still face many challenges, both technical and social. For instance, on the technical side, should robots be programmed with safety rules, or should they be created with the ability for safety-oriented reasoning? Should robot ethics be based on human-centered value systems, or a combination of human-centered value systems with the robot’s own value system? Or, legally, when a robot accident does occur, how should the responsibility be divided (for example, among the designer, manufacturer, user, or even the robot itself)?
Weng also indicated that, as robots become more integrated into human society, the importance of a legal framework for social robotics will become more obvious. He predicted that determining how to maintain a balance between human-robot interaction (robot technology development) and social system design (a legal regulation framework) will present the biggest challenges in safety when the human-robot coexistence society emerges.
More information:
http://www.yhweng.tw
“Toward the Human-Robot Co-Existence Society: On Safety Intelligence for Next Generation Robots.” Yueh-Hsuan Weng, Chien-Hsun Chen, and Chuen-Tsai Sun. International Journal of Social Robotics. DOI 10.1007/s12369-009-0019-1.

World's First Controllable Molecular Gear At Nanoscale Created

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ScienceDaily (June 22, 2009) — Scientists from A*STAR’s Institute of Materials Research and Engineering (IMRE), led by Professor Christian Joachim,* have scored a breakthrough in nanotechnology by becoming the first in the world to invent a molecular gear of the size of 1.2nm whose rotation can be deliberately controlled. This achievement marks a radical shift in the scientific progress of molecular machines and is published on 14 June 20009 in Nature Materials.

Said Prof Joachim, “Making a gear the size of a few atoms is one thing, but being able to deliberately control its motions and actions is something else altogether. What we’ve done at IMRE is to create a truly complete working gear that will be the fundamental piece in creating more complex molecular machines that are no bigger than a grain of sand.”
Prof Joachim and his team discovered that the way to successfully control the rotation of a single-molecule gear is via the optimization of molecular design, molecular manipulation and surface atomic chemistry. This was a breakthrough because before the team’s discovery, motions of molecular rotors and gears were random and typically consisted of a mix of rotation and lateral displacement. The scientists at IMRE solved this scientific conundrum by proving that the rotation of the molecule-gear could be well-controlled by manipulating the electrical connection between the molecule and the tip of a Scanning Tunnelling Microscope while it was pinned on an atom axis.
Said Dr Lim Khiang Wee, Executive Director of IMRE, “Christian and his team’s discovery shows that it may one day be possible to create and manipulate molecular-level machines. Such machines may, for example, walk on DNA tracks in the future to deliver therapeutics to heal and cure. There already exists at least one international roadmap for creating such productive nanosystems. As we push the frontiers of nanotechnology, we increase our understanding of new phenomena at the nanoscale. This paper is a valuable step on the long road to applying this understanding for discoveries and breakthroughs in nanotechnology and bring to reality the tiny nanobots and nanomachines from science fiction movies.”
*Prof Christian Joachim is a Visiting Investigator at IMRE since 2005. He is the Director of Research, and Head of Molecular Nanoscience and Picotechnology Group, atthe Centre National de la Recherché Scientifique (CNRS).
Journal reference:
C. Manzano, W.-H. Soe, H. S. Wong, F. Ample, A. Gourdon, N. Chandrasekhar & C. Joachim. Step-by-step rotation of a molecule-gear mounted on an atomic-scale axis. Nature Materials, Published online: 14 June 2009 DOI: 10.1038/NMAT2467
Adapted from materials provided by Agency for Science, Technology and Research (A*STAR), Singapore.

Scientists Break Light Modulation Speed Record -- Twice

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ScienceDaily (June 22, 2009) — Researchers have constructed a light-emitting transistor that has set a new record with a signal-processing modulation speed of 4.3 gigahertz, breaking the previous record of 1.7 gigahertz held by a light-emitting diode.

But, the researchers didn't stop there. By internally connecting the base and collector of a light-emitting transistor, they created a new form of light-emitting diode, which modulates at up to 7 gigahertz, breaking the speed record once again.
In a pair of papers published in the June 15 issue of Applied Physics Letters, researchers at the University of Illinois and at U. of I. licensee Quantum Electro Opto Systems in Melaka, Malaysia, report the fabrication and testing of the new high-speed light-emitting transistor and the new "tilted-charge" light-emitting diode.
"Simple in design and construction, the tilted-charge light-emitting diode offers an attractive alternative for use in high-speed signal processing, optical communication systems and integrated optoelectronics," said Nick Holonyak Jr., a John Bardeen Chair Professor of Electrical and Computer Engineering and Physics at Illinois, and a co-author of both papers.
The modulation speed of either a light-emitting diode or a light-emitting transistor is limited by the rate at which electrons and holes (the minus and plus charges – the carriers of current) recombine. The recombination lifetime is important in determining device speed.
With a usual "slow" recombination process, the speed of a light-emitting diode is limited to approximately 1.7 gigahertz, which corresponds to a carrier lifetime of 100 picoseconds. For more than 40 years, scientists thought breaking the 100-picosecond barrier was impossible.
Recombination speeds of less than 100 picoseconds are not readily achieved in light-emitting diodes because equal number densities of electrons and holes are injected into the active region to preserve charge neutrality, said Holonyak, who invented the first practical visible light-emitting diode more than 40 years ago.
These charges become stuck, stacked-up waiting to recombine, Holonyak said. To achieve high recombination speeds, an extremely high injection level and a very high charge population are required in light-emitting diodes. These conditions are not necessary in transistors, however.
"Unlike a diode, a transistor does not store charge," said Milton Feng, the Holonyak Chair Professor of Electrical and Computer Engineering, and a co-author of the two papers. "Charges are delivered to the transistor's quantum well active region, where they either recombine almost instantly, or they are kept moving on out of the device. The charges do not become stacked-up, waiting to recombine with their oppositely charged twins."
To increase the modulation speed of their light-emitting transistor, the researchers reduced the emitter size, increased the so-called collector thickness (the third terminal region), and utilized a special internal common collector design. These changes resulted in a faster signal at a very low current level, and at low heat dissipation.
Having a "fast" recombination process, the modulation speed of the light-emitting transistor was measured at 4.3 gigahertz, which corresponds to a recombination lifetime of 37 picoseconds, well under the "100-picosecond barrier."
"In the light-emitting transistor, the third terminal – the collector – effectively 'tilts' the charge and removes carriers with slower recombination lifetimes," said Holonyak, who also is a professor in the university's Center for Advanced Study, one of the highest forms of campus recognition.
"As opposed to the charge 'pile-up' condition found in a normal diode, the dynamic 'tilted' charge flow condition in the transistor base is maintained with the collector in competition with the base recombination process," Holonyak said. "If the charge doesn't recombine and generate a photon fast enough, it is swept away by the current in the collector."
By preventing the build-up of "slow" charges in the base, the "fast" picosecond recombination dynamics also provided the basis for the researchers' light-emitting transistor rewired internally as a new type of light-emitting diode.
The tilted-charge light-emitting diode achieved a record-breaking modulation speed of 7 gigahertz, corresponding to a recombination lifetime of 23 picoseconds.
"The tilted-charge light-emitting diode is simple to make, low cost, and easy to package and use," Holonyak said.
Because of the tilted base population in the device, current flow, which is a function of the slope of the charge distribution, makes possible high current densities without requiring extreme carrier densities.
"That's the trick of the transistor," Holonyak said. "And now we've incorporated it into a diode. The physics has been there all along. It just wasn't recognized."
With Feng and Holonyak, co-authors of the paper are lead author Gabriel Walter (chief executive officer at Quantum Electro Opto Systems), and graduate students Chao-Hsin Wu and Han Wui Then.
Funding was provided by the U.S. Army Research Office and the Brain Gain Malaysia Diaspora Program. Device fabrication and testing was performed at the university's Micro and Nanotechnology Laboratory.
Quantum Electro Opto Systems is a company formed by Walter, Feng and Holonyak to commercialize the light-emitting transistor and tilted-charge light-emitting diode technology.
Adapted from materials provided by University of Illinois at Urbana-Champaign.

Strong Freestanding Nanoparticle Films Created Without Fillers

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ScienceDaily (June 19, 2009) — Nanoparticle films are no longer a delicate matter: Vanderbilt physicists have found a way to make them strong enough so they don’t disintegrate at the slightest touch.

In the last 25 years, ever since scientists figured out how to create nanoparticles – ultrafine particles with diameters less than 100 nanometers – they have come up with a number of different methods to mold them into thin films which have a variety of interesting potential applications ranging from semiconductor fabrication to drug delivery, solid state lighting to flexible television and computer displays.
Until now these films have had a common problem: lack of cohesion. Nanoparticles typically consist of an inorganic core coated with a thin layer of organic molecules. These particles are not very sticky so they don’t form coherent thin films unless they are encapsulated in a polymer coating or mixed with molecules called chemical “cross-linkers” that act like glue to stick the nanoparticles together.
“Adding this extra material can complicate the fabrication of nanoparticle films and make them more expensive. In addition, the added material, usually a polymer, can modify the physical properties that make these films so interesting,” says James Dickerson, assistant professor of physics at Vanderbilt, who headed the research group that created the freestanding nanoparticle films without any additives.
The properties of the new films and the method that the researchers use to create them is described in the article “Sacrificial layer electrophoretic deposition of freestanding multilayered nanoparticle films” published online in the journal Chemical Communications on May 27, 2009.
“Our films are so resilient that we can pick them up with a pair of tweezers and move them around on a surface without tearing,” says Dickerson. “This makes it particularly easy to put them into microelectronic devices, such as computer chips.”
Dickerson considers the most straightforward applications for his films to be in semiconductor manufacturing to aid in the continued miniaturization of digital circuitry and in the production of flexible television and computer screens.
A key component in the transistors in integrated circuits is an insulating layer that separates the gate, which turns current flow on and off, from the channel through which the current flows. Traditionally, semiconductor manufacturers have used silicon dioxide for this purpose. As transistors have shrunk, however, they have been forced to make this layer thinner and thinner until they reached the point where electrons leak through and sap the power from the device. This has led semiconductor manufacturers to retool their process to use “high-k” dielectric materials, such as hafnium oxide, because they have much higher electrical resistance.
“We have made high-k nanoparticle films that could be cheaper and more effective than the high-k materials the manufacturers are currently using,” Dickerson says.
In addition, the physicist argues that the films have properties that make them ideal for flexible television and computer screens. They are very flexible and don’t show any signs of cracking when they are flexed repeatedly. They are also made using a technique called electrophoretic deposition (EPD) that is well suited for creating patterned material and is compatible with fluorescent materials that can form the red, green and blue pixels used in flat panel television screens and computer displays.
EDP is a wet method. Nanoparticles are placed in a solution along with a pair of electrodes. When an electric current is applied, it creates an electrical field in the liquid that attracts the nanoparticles, which coat the electrodes. Using colloids, mixtures with particles 10 to 1,000 times larger than nanoparticles, EDP is widely used to apply coatings to complex metal parts such as automobile bodies, prosthetic devices, appliances and beverage containers. It is only recently that researchers like Dickerson have begun applying the technique to nanoparticles.
“The science of colloidal EDP is well known but the particles are substantially larger than the solvent molecules. Many nanoparticles, however, are about the same size as the solvent molecules, which makes the process considerably more complicated and difficult to control,” Dickerson explains.
To get the method to work, in fact, Dickerson and his colleagues had to invent of new form of EDP, which they call sacrificial layer electrophoretic deposition. They added a spun-cast layer of polymer to the electrodes that serves as a pattern that organizes the nanoparticles as they are deposited. Then, after the deposition process is completed, they dissolve (sacrifice) the polymer layer to free the nanoparticle film.
According to the researchers, films made in this fashion stick together because the electrical field slams the nanoparticles into the film with sufficient force to pack the particles together tightly enough to allow naturally attractive inter-particle forces to bind the particles together.
So far the Dickerson group has used the technique to make films out of two different types of nanoparticles – iron oxide and cadmium selenide – and they believe the technique can be used with a wide variety of other nanoparticles.
“The technique is liberating because you can make these films from the materials you want and use them where you want,” Dickerson says.
The co-authors on the paper are graduate students Saad A. Hasan and Dustin W. Kavich. The research was funded by a grant from Vanderbilt University.
Adapted from materials provided by Vanderbilt University.

Fish Robot As An Alternative Marine Propulsion System Of The Future

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ScienceDaily (June 11, 2009) — The team of Darmstadt researchers analyzed videos of fish’s motions and then developed a prototype fish robot that duplicated them, and are now testing it using the locomotional patterns of various species of fish in order to refine it and improve its efficiency.

Their fish robot, dubbed “Smoky,” consists of a “skeleton” composed of ten segments enshrouded in an elastic skin that are free to move relative to one another and caused to undergo snaking motions similar to those of fish by waterproof actuators. Including its tail fin, the fish robot, which is a 5:1 scale model of a gilt-head sea bream, is 1.50 meters long.
The researchers hope that use of their fish robot for ship propulsion will help prevent shoreline erosion and the underminings of submarine installations caused by ships’ screws. The fish robot’s “soft” drive action should also prevent the churning up of seabeds and riverbeds and its effects on marine plants and aquatic-animal populations.
Adapted from materials provided by Technische Universität Darmstadt, via AlphaGalileo.

Researchers create freestanding nanoparticle films without fillers

Source: http://www.physorg.com/news163770109.html

Nanoparticle films are no longer a delicate matter: Vanderbilt physicists have found a way to make them strong enough so they don't disintegrate at the slightest touch.

In the last 25 years, ever since scientists figured out how to create nanoparticles - ultrafine particles with diameters less than 100 nanometers - they have come up with a number of different methods to mold them into thin films which have a variety of interesting potential applications ranging from semiconductor fabrication to drug delivery, solid state lighting to flexible television and computer displays.
Until now these films have had a common problem: lack of cohesion. Nanoparticles typically consist of an inorganic core coated with a thin layer of organic molecules. These particles are not very sticky so they don't form coherent thin films unless they are encapsulated in a polymer coating or mixed with molecules called chemical "cross-linkers" that act like glue to stick the nanoparticles together.
"Adding this extra material can complicate the fabrication of nanoparticle films and make them more expensive. In addition, the added material, usually a polymer, can modify the physical properties that make these films so interesting," says James Dickerson, assistant professor of physics at Vanderbilt, who headed the research group that developed freestanding nanoparticle films without any additives.
The properties of the new films and the method that the researchers use to create them is described in the article "Sacrificial layer electrophoretic deposition of freestanding multilayered nanoparticle films" published online in the journal Chemical Communications on May 27, 2009.
"Our films are so resilient that we can pick them up with a pair of tweezers and move them around on a surface without tearing," says Dickerson. "This makes it particularly easy to put them into microelectronic devices, such as computer chips."
Dickerson considers the most straightforward applications for his films to be in semiconductor manufacturing to aid in the continued miniaturization of digital circuitry and in the production of flexible television and computer screens.

A key component in the transistors in integrated circuits is an insulating layer that separates the gate, which turns current flow on and off, from the channel through which the current flows. Traditionally, semiconductor manufacturers have used silicon dioxide for this purpose. As transistors have shrunk, however, they have been forced to make this layer thinner and thinner until they reached the point where electrons leak through and sap the power from the device. This has led semiconductor manufacturers to retool their process to use "high-k" dielectric materials, such as hafnium oxide, because they have much higher electrical resistance.
"We have made high-k nanoparticle films that could be cheaper and more effective than the high-k materials the manufacturers are currently using," Dickerson says.
In addition, the physicist argues that the films have properties that make them ideal for flexible television and computer screens. They are very flexible and don't show any signs of cracking when they are flexed repeatedly. They are also made using a technique called electrophoretic deposition (EPD) that is well suited for creating patterned material and is compatible with fluorescent materials that can form the red, green and blue pixels used in flat panel television screens and computer displays.
EDP is a wet method. Nanoparticles are placed in a solution along with a pair of electrodes. When an electric current is applied, it creates an electrical field in the liquid that attracts the nanoparticles, which coat the electrodes. Using colloids, mixtures with particles 10 to 1,000 times larger than nanoparticles, EDP is widely used to apply coatings to complex metal parts such as automobile bodies, prosthetic devices, appliances and beverage containers. It is only recently that researchers like Dickerson have begun applying the technique to nanoparticles.
"The science of colloidal EDP is well known but the particles are substantially larger than the solvent molecules. Many nanoparticles, however, are about the same size as the solvent molecules, which makes the process considerably more complicated and difficult to control," Dickerson explains.
To get the method to work, in fact, Dickerson and his colleagues had to invent of new form of EDP, which they call sacrificial layer electrophoretic deposition. They added a spun-cast layer of polymer to the electrodes that serves as a pattern that organizes the nanoparticles as they are deposited. Then, after the deposition process is completed, they dissolve (sacrifice) the polymer layer to free the nanoparticle film.
According to the researchers, films made in this fashion stick together because the electrical field slams the nanoparticles into the film with sufficient force to pack the particles together tightly enough to allow naturally attractive inter-particle forces to bind the particles together.
So far the Dickerson group has used the technique to make films out of two different types of nanoparticles - iron oxide and cadmium selenide - and they believe the technique can be used with a wide variety of other nanoparticles.
"The technique is liberating because you can make these films from the materials you want and use them where you want," Dickerson says.
Source: Vanderbilt University (news : web)

New Radio Chip Mimics Human Ear

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ScienceDaily (June 4, 2009) — MIT engineers have built a fast, ultra-broadband, low-power radio chip, modeled on the human inner ear, that could enable wireless devices capable of receiving cell phone, Internet, radio and television signals.

Rahul Sarpeshkar, associate professor of electrical engineering and computer science, and his graduate student, Soumyajit Mandal, designed the chip to mimic the inner ear, or cochlea. The chip is faster than any human-designed radio-frequency spectrum analyzer and also operates at much lower power.
"The cochlea quickly gets the big picture of what's going on in the sound spectrum," said Sarpeshkar. "The more I started to look at the ear, the more I realized it's like a super radio with 3,500 parallel channels."
Sarpeshkar and his students describe their new chip, which they have dubbed the "radio frequency (RF) cochlea," in a paper to be published in the June issue of the IEEE Journal of Solid-State Circuits. They have also filed for a patent to incorporate the RF cochlea in a universal or software radio architecture that is designed to efficiently process a broad spectrum of signals including cellular phone, wireless Internet, FM, and other signals.
The RF cochlea mimics the structure and function of the biological cochlea, which uses fluid mechanics, piezoelectrics and neural signal processing to convert sound waves into electrical signals that are sent to the brain.
As sound waves enter the cochlea, they create mechanical waves in the cochlear membrane and the fluid of the inner ear, activating hair cells (cells that cause electrical signals to be sent to the brain). The cochlea can perceive a 100-fold range of frequencies -- in humans, from 100 to 10,000 Hz. Sarpeshkar used the same design principles in the RF cochlea to create a device that can perceive signals at million-fold higher frequencies, which includes radio signals for most commercial wireless applications.
The device demonstrates what can happen when researchers take inspiration from fields outside their own, says Sarpeshkar.
"Somebody who works in radio would never think of this, and somebody who works in hearing would never think of it, but when you put the two together, each one provides insight into the other," he says. For example, in addition to its use for radio applications, the work provides an analysis of why cochlear spectrum analysis is faster than any known spectrum-analysis algorithm. Thus, it sheds light on the mechanism of hearing as well.
The RF cochlea, embedded on a silicon chip measuring 1.5 mm by 3 mm, works as an analog spectrum analyzer, detecting the composition of any electromagnetic waves within its perception range. Electromagnetic waves travel through electronic inductors and capacitors (analogous to the biological cochlea's fluid and membrane). Electronic transistors play the role of the cochlea's hair cells.
The analog RF cochlea chip is faster than any other RF spectrum analyzer and consumes about 100 times less power than what would be required for direct digitization of the entire bandwidth. That makes it desirable as a component of a universal or "cognitive" radio, which could receive a broad range of frequencies and select which ones to attend to.
Biological inspiration
This is not the first time Sarpeshkar has drawn on biology for inspiration in designing electronic devices. Trained as an engineer but also a student of biology, he has found many similar patterns in the natural and man-made worlds. For example, Sarpeshkar's group, in MIT's Research Laboratory of Electronics, has also developed an analog speech-synthesis chip inspired by the human vocal tract and a novel analysis-by-synthesis technique based on the vocal tract. The chip's potential for robust speech recognition in noise and its potential for voice identification have several applications in portable devices and security applications.
The researchers have built circuits that can analyze heart rhythms for wireless heart monitoring, and are also working on projects inspired by signal processing in cells. In the past, his group has worked on hybrid analog-digital signal processors inspired by neurons in the brain.
Sarpeshkar says that engineers can learn a great deal from studying biological systems that have evolved over hundreds of millions of years to perform sensory and motor tasks very efficiently in noisy environments while using very little power.
"Humans have a long way to go before their architectures will successfully compete with those in nature, especially in situations where ultra-energy-efficient or ultra-low-power operation are paramount," he said. Nevertheless, "We can mine the intellectual resources of nature to create devices useful to humans, just as we have mined her physical resources in the past.
Journal reference:
Mandal, S.; Zhak, S. M.; Sarpeshkar, R. A Bio-Inspired Active Radio-Frequency Silicon Cochlea. IEEE Journal of Solid-State Circuits, 2009; 44 (6): 1814-1828 DOI: 10.1109/JSSC.2009.2020465
Adapted from materials provided by Massachusetts Institute of Technology.

Motion Capture Technology Takes A Leap Forward

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ScienceDaily (June 4, 2009) — A juggler and a conductor were among the artists who helped create a device which can retrieve dozens of different movement sequences in a matter of minutes.

Motion capture tools are used by the performing arts for everything from live productions to creative screen-bound works, choreographic notation and archiving, but it is difficult to identify required sequences for a given project amid the mass of data these tools generate.
Led by principal investigator Sally Jane Norman, director of Newcastle University's Culture Lab (http://culturelab.ncl.ac.uk/amuc/), researchers have come up with a prototype data retrieval tool which makes selecting movement features or sequences much easier: the user 'sketches' the required movement with a mouse or pen and this triggers a search for a similar sequence.
Details of the research are being published online in the Royal Society journal Philosophical Transactions of the Royal Society A.
"Capturing human movement data theoretically interests a variety of people, but its actual usefulness depends on how effectively data retrieval and analysis can be performed," explained Dr Norman. "This development opens up far more cross-sector opportunities, making human motion capture a rich area of interdisciplinary investigation twenty years after the animation industry first teamed up with biomechanics experts."
As performing artists can accurately reproduce complex gestures and adopt novel creative approaches, they are ideal test subjects for developers tracking human movement.
Motion capture works across many disciplines, with artistic performance skills combined with research from sectors such as biomechanics, sensor development and information processing.
In addition to the biomedical sector, where movement is monitored for diagnostic or corrective purposes, motion capture libraries are increasingly being used by the cinematographic and games industries, and in education, advertising, training manuals and simulators.
Adapted from materials provided by Newcastle University.

Drinking Water From Air Humidity

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ScienceDaily (June 5, 2009) — Not a plant to be seen, the desert ground is too dry. But the air contains water, and research scientists have found a way of obtaining drinking water from air humidity. The system is based completely on renewable energy and is therefore autonomous.

Cracks permeate the dried-out desert ground, the landscape bears testimony to the lack of water. But even here, where there are no lakes, rivers or groundwater, considerable quantities of water are stored in the air. In the Negev desert in Israel, for example, annual average relative air humidity is 64 percent – in every cubic meter of air there are 11.5 milliliters of water.
Research scientists at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart working in conjunction with their colleagues from the company Logos Innovationen have found a way of converting this air humidity autonomously and decentrally into drinkable water. “The process we have developed is based exclusively on renewable energy sources such as thermal solar collectors and photovoltaic cells, which makes this method completely energy-autonomous. It will therefore function in regions where there is no electrical infrastructure,” says Siegfried Egner, head of department at the IGB. The principle of the process is as follows: hygroscopic brine – saline solution which absorbs moisture – runs down a tower-shaped unit and absorbs water from the air. It is then sucked into a tank a few meters off the ground in which a vacuum prevails. Energy from solar collectors heats up the brine, which is diluted by the water it has absorbed.
Because of the vacuum, the boiling point of the liquid is lower than it would be under normal atmospheric pressure. This effect is known from the mountains: as the atmospheric pressure there is lower than in the valley, water boils at temperatures distinctly below 100 degrees Celsius. The evaporated, non-saline water is condensed and runs down through a completely filled tube in a controlled manner. The gravity of this water column continuously produces the vacuum and so a vacuum pump is not needed. The reconcentrated brine runs down the tower surface again to absorb moisture from the air.
“The concept is suitable for various sizes of installation. Single-person units and plants supplying water to entire hotels are conceivable,” says Egner. Prototypes have been built for both system components – air moisture absorption and vacuum evaporation – and the research scientists have already tested their interplay on a laboratory scale. In a further step the researchers intend to develop a demonstration facility.
Adapted from materials provided by Fraunhofer-Gesellschaft.

Biomimetic-engineering Design Can Replace Spaghetti Tangle Of Nanotubes In Novel Material

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ScienceDaily (June 5, 2009) — Nanoelectromechanical systems (NEMS) devices have the potential to revolutionize the world of sensors: motion, chemical, temperature, etc. But taking electromechanical devices from the micro scale down to the nano requires finding a means to dissipate the heat output of this tiny gadgetry.

In a paper appearing in the March 26 issue of Nano Letters, Professor Markus Buehler and postdoctoral associate Zhiping Xu of MIT’s Department of Civil and Environmental Engineering say the solution is to build these devices using a thermal material that naturally dissipates heat from the device’s center through a hierarchical branched network of carbon nanotubes. The template for this thermal material’s design is a living cell, specifically, the hierarchical protein networks that allow a cell’s nucleus to communicate with the cell’s outermost regions.
“The structure now used when designing materials with carbon nanotubes resembles spaghetti,” said Buehler, who studies protein-based materials at the nano and atomistic scales with the goal of using biomimetic-engineering principles to design human-made materials. “We show that a precise arrangement of carbon nanotubes similar to those found in the cytoskeleton of cells will create a thermal material that effectively dissipates heat, which could prevent a NEMS device from failing or melting.”
NEMS devices are characterized by extremely small, high-density heat sources that can’t be cooled by traditional means. Even the microelectromechanical systems (MEMS) devices used in automobiles and electronics are hard to cool, because conventional thermal management strategies such as fans, fluids, pastes and wiring often don’t work at these small scales; heat buildup in MEMS frequently leads to catastrophic device failure, which limits the reliability of larger systems.
But the number of heat-conducting fibers or carbon nanotubes (CNTs) that can be connected to the heat source at the center of a NEMS device is limited by the physical size of the heat source itself. Buehler and Xu demonstrate that a simple geometric structure — a branched-tree hierarchy of at least two branches sprouting off each branch — is far more effective at heat dissipation than the non-hierarchical “spaghetti” of most existing CNT-based material.
They show that a single fiber (or branch) connected to the heat source, with 99 additional branched links between it and the heat sink, will provide the same dissipation effect as if 50 long fibers were connected directly to the heat source. If five carbon nanotubes are arranged in direct connection to the heat source, each of which uses this branched-tree hierarchical structure, the heat dissipation will be the equivalent of 250 direct connections from the heat source to an external heat sink.
“Our paper provides a breakthrough in the understanding of how nanostructural elements can be utilized effectively to bridge scales from the nano to macro through formation of hierarchical structures,” said Xu. “The results could change the way nanodevices are designed and fabricated by enabling technological innovations for highly integrated systems.”
This research is funded by DARPA (the U.S. Defense Advanced Research Projects Agency) and the MIT Energy Initiative.
Adapted from materials provided by Massachusetts Institute of Technology, Department of Civil and Environmental Engineering.

Aluminum-oxide Nanopore Beats Other Materials For DNA Analysis

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ScienceDaily (June 5, 2009) — Fast and affordable genome sequencing has moved a step closer with a new solid-state nanopore sensor being developed by researchers at the University of Illinois.

The nanopore sensor, made by drilling a tiny hole through a thin film of aluminum oxide, could ultimately prove capable of performing DNA analysis with a single molecule, offering tremendous possibilities for personalized medicine and advanced diagnostics.
"Solid-state nanopore sensors have shown superior chemical, thermal and mechanical stability over their biological counterparts, and can be fabricated using conventional semiconductor processes," said Rashid Bashir, a Bliss Professor of electrical and computer engineering and bioengineering, and the director of the university's Micro and Nanotechnology Laboratory.
"The aluminum-oxide nanopore sensors go a step further," Bashir said, "exhibiting superior mechanical properties, enhanced noise performance and increased lifetime over their silicon-oxide and silicon-nitride counterparts."
The researchers describe the fabrication and operation of the aluminum-oxide nanopore sensor in a paper accepted for publication in Advanced Materials, and posted on the journal's Web site.
To make the sensor, the researchers begin by using a technique called atomic layer deposition to produce a very thin film of aluminum oxide on a silicon substrate.
Next, the central portion of the substrate is etched away, leaving the film as a suspended membrane. An electron beam is then used to create a very tiny hole – a nanopore – in the membrane.
The process of making the nanopore resulted in an unexpected bonus, Bashir said. "As the electron beam forms the nanopore, it also heats the surrounding material, forming nanocrystallites around the nanopore. These crystals help to improve the mechanical integrity of the nanopore structure and could potentially improve noise performance as well."
The nanopore sensors described in the paper had pore diameters ranging in size from 4 to 16 nanometers, and a film thickness of approximately 50 nanometers. Thinner membranes are possible with atomic layer deposition, Bashir said, and would offer higher resolution of the detection.
"Thinner membranes can produce less noise as a molecule travels through the nanopore," said Bashir, who is also affiliated with the university's Beckman Institute, the Frederick Seitz Materials Research Laboratory, and the Institute for Genomic Biology. "Ultimately, we'd like to make our membranes as thin as biological membranes, which are about 5 nanometers thick."
To demonstrate the functionality of the aluminum-oxide nanopores, the researchers performed experiments with pieces of DNA containing approximately 5,000 base pairs. Bashir's team verified the detection of single molecules, with a signal-to-noise performance comparable to that achieved with other solid-state nanopore technology.
"More work must be done to achieve single base resolution, however," Bashir said. "Our next step is to detect and measure significantly shorter molecules."
With Bashir, co-authors of the paper are graduate students Bala Murali Venkatesan (lead author), Brian Dorvel, Sukru Yemenicioglu and Nicholas Watkins, and principal research scientist Ivan Petrov.
Funding was provided by the National Institutes of Health.
Adapted from materials provided by University of Illinois at Urbana-Champaign.

New, Light-driven Nanomotor Is Simpler, More Promising, Scientists Say

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ScienceDaily (June 5, 2009) — Sunflowers track the sun as it moves from east to west. But people usually have to convert sunlight into electricity or heat to put its power to use.

Now, a team of University of Florida chemists is the latest to report a new mechanism to transform light straight into motion – albeit at a very, very, very tiny scale.
In a paper expected to appear soon in the online edition of the journal Nano Letters, the UF team reports building a new type of "molecular nanomotor" driven only by photons, or particles of light. While it is not the first photon-driven nanomotor, the almost infinitesimal device is the first built entirely with a single molecule of DNA — giving it a simplicity that increases its potential for development, manufacture and real-world applications in areas ranging from medicine to manufacturing, the scientists say.
"It is easy to assemble, has fewer parts and theoretically should be more efficient," said Huaizhi Kang, a doctoral student in chemistry at UF and the first author of the paper.
The scale of the nanomotor is almost vanishingly small.
In its clasped, or closed, form, the nanomotor measures 2 to 5 nanometers — 2 to 5 billionths of a meter. In its unclasped form, it extends as long as 10 to 12 nanometers. Although the scientists say their calculations show it uses considerably more of the energy in light than traditional solar cells, the amount of force it exerts is proportional to its small size.
But that won't necessarily limit its potential.
In coming years, the nanomotor could become a component of microscopic devices that repair individual cells or fight viruses or bacteria. Although in the conceptual stage, those devices, like much larger ones, will require a power source to function. Because it is made of DNA, the nanomotor is biocompatible. Unlike traditional energy systems, the nanomotor also produces no waste when it converts light energy into motion.
"Preparation of DNA molecules is relatively easy and reproducible, and the material is very safe," said Yan Chen, a UF chemistry doctoral student and one of the authors of the paper.
Applications in the larger world are more distant. Powering a vehicle, running an assembly line or otherwise replacing traditional electricity or fossil fuels would require untold trillions of nanomotors, all working together in tandem — a difficult challenge by any measure.
"The major difficulty lies ahead," said Weihong Tan, a UF professor of chemistry and physiology, author of the paper and the leader of the research group reporting the findings. "That is how to collect the molecular level force into a coherent accumulated force that can do real work when the motor absorbs sunlight."
Tan added that the group has already begun working on the problem.
"Some prototype DNA nanostructures incorporating single photo-switchable motors are in the making which will synchronize molecular motions to accumulate forces," he said.
To make the nanomotor, the researchers combined a DNA molecule they created in the lab with azobenzene, a chemical compound that responds to light. A high-energy photon prompts one response; lower energy another.
To demonstrate the movement, the researchers attached a fluorophore, or light-emitter, to one end of the nanomotor and a quencher, which can quench the emitting light, to the other end. Their instruments recorded emitted light intensity that corresponded to the motor movement.
"Radiation does cause things to move from the spinning of radiometer wheels to the turning of sunflowers and other plants toward the sun," said Richard Zare, distinguished professor and chairman of chemistry at Stanford University. "What Professor Tan and co-workers have done is to create a clever light-actuated nanomotor involving a single DNA molecule. I believe it is the first of its type."
The National Institutes of Health and the National Science Foundation funded the research. The other coauthors of this paper are Haipeng Liu, Joseph A. Phillips, Zehui Cao, Youngmi Kim, Zunyi Yang and Jianwei Li.
Adapted from materials provided by University of Florida.

Electronic Memory Chips That Can Bend And Twist

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ScienceDaily (June 3, 2009) — Electronic memory chips may soon gain the ability to bend and twist as a result of work by engineers at the National Institute of Standards and Technology (NIST). As reported in the July 2009 issue of IEEE Electron Device Letters, the engineers have found a way to build a flexible memory component out of inexpensive, readily available materials.

Though not yet ready for the marketplace, the new device is promising not only because of its potential applications in medicine and other fields, but because it also appears to possess the characteristics of a memristor, a fundamentally new component for electronic circuits that industry scientists developed in 2008. NIST has filed for a patent on the flexible memory device (application #12/341.059).
Electronic components that can flex without breaking are coveted by portable device manufacturers for many reasons—and not just because people have a tendency to drop their mp3 players. Small medical sensors that can be worn on the skin to monitor vital signs such as heart rate or blood sugar could benefit patients with conditions that require constant maintenance, for example. Though some flexible components exist, creating flexible memory has been a technical barrier, according to NIST researchers.
Hunting for a solution, the researchers took polymer sheets—the sort that transparencies for overhead projectors are made from—and experimented with depositing a thin film of titanium dioxide, an ingredient in sunscreen, on their surfaces. Instead of using expensive equipment to deposit the titanium dioxide as is traditionally done, the material was deposited by a sol gel process, which consists of spinning the material in liquid form and letting it set, like making gelatin. By adding electrical contacts, the team created a flexible memory switch that operates on less than 10 volts, maintains its memory when power is lost, and still functions after being flexed more than 4,000 times.
What's more, the switch's performance bears a strong resemblance to that of a memristor, a component theorized in 1971 as a fourth fundamental circuit element (along with the capacitor, resistor and inductor). A memristor is, in essence, a resistor that changes its resistance depending on the amount of current that is sent through it—and retains this resistance even after the power is turned off. Industrial scientists announced they had created a memristor last year, and the NIST component demonstrates similar electrical behavior, but is also flexible. Now that the team has successfully fabricated a memristor, NIST can begin to explore the metrology that may be necessary to study the device's unique electrical behavior.
"We wanted to make a flexible memory component that would advance the development and metrology of flexible electronics, while being economical enough for widespread use," says NIST researcher Nadine Gergel-Hackett. "Because the active component of our device can be fabricated from a liquid, there is the potential that in the future we can print the entire memory device as simply and inexpensively as we now print a slide on an overhead transparency."
Journal references:
N. Gergel-Hackett, B. Hamadani, B. Dunlap, J. Suehle, C. Richter, C. Hacker, D. Gundlach. A flexible solution-processed memristor. IEEE Electron Device Letters, 2009; 30 (7) DOI: 10.1109/LED.2009.2021418
D. B. Strukov, G. S. Snider, D. R. Stewart, and S. R. Williams. The missing memristor found. Nature, 2008; 453 (7191): 80 DOI: 10.1038/nature06932
Adapted from materials provided by National Institute of Standards and Technology.