Novel Artificial Material Could Facilitate Wireless Power

This advance is made possible by the recent ability to fabricate exotic composite materials known as metamaterials, which are not so much a single substance, but an entire human-made structure that can be engineered to exhibit properties not readily found in nature. In fact, the metamaterial used in earlier Duke studies, and which would likely be used in future wireless power transmission systems, resembles a miniature set of tan Venetian blinds.

Theoretically, this metamaterial can improve the efficiency of"recharging" devices without wires. As power passes from the transmitting device to the receiving device, most if not all of it scatters and dissipates unless the two devices are extremely close together. However, the metamaterial postulated by the Duke researchers, which would be situated between the energy source and the"recipient" device, greatly refocuses the energy transmitted and permits the energy to traverse the open space between with minimal loss of power.

"We currently have the ability to transmit small amounts of power over short distances, such as in radio frequency identification (RFID) devices," said Yaroslav Urzhumov, assistant research professor in electrical and computer engineering at Duke's Pratt School of Engineering."However, larger amounts of energy, such as that seen in lasers or microwaves, would burn up anything in its path.

"Based on our calculations, it should be possible to use these novel metamaterials to increase the amount of power transmitted without the negative effects," Urzhumov said.

The results of the Duke research were published online in the journalPhysical Review B. Urzhumov works in the laboratory of David R. Smith, William Bevan Professor of electrical and computer engineering at Pratt School of Engineering. Smith's team was the first demonstrate that similar metamaterials could act as a cloaking device in 2006.

Just as the metamaterial in the cloaking device appeared to make a volume of space"disappear," in the latest work, the metamaterial would make it seem as if there was no space between the transmitter and the recipient, Urzhumov said. Therefore, he said, the loss of power should be minimal.

Urzhumov's research is an offshoot of"superlens" research conducted in Smith's laboratory. Traditional lenses get their focusing power by controlling rays as they pass through the two outside surfaces of the lens. On the other hand, the superlens, which is in fact a metamaterial, directs waves within the bulk of the lens between the outside surfaces, giving researchers a much greater control over whatever passes through it.

The metamaterial used in wireless power transmission would likely be made of hundreds to thousands -- depending on the application -- of individual thin conducting loops arranged into an array. Each piece is made from the same copper-on-fiberglass substrate used in printed circuit boards, with excess copper etched away. These pieces can then be arranged in an almost infinite variety of configurations.

"The system would need to be tailored to the specific recipient device, in essence the source and target would need to be 'tuned' to each other," Urzhumov said."This new understanding of how matematerials can be fabricated and arranged should help make the design of wireless power transmission systems more focused."

The analysis performed at Duke was inspired by recent studies at Mitsubishi Electric Research Labs (MERL), an industrial partner of the Duke Center for Metamaterials and Integrated Plasmonics. MERL is currently investigating metamaterials for wireless power transfer. The Duke researchers said that with these new insights into the effects of metamaterials, developing actual devices can be more targeted and efficient.

The Duke University research was supported by a Multidisciplinary University Research Initiative (MURI) grant through the Air Force Office of Scientific Research and the U.S. Army Research Office.

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Autonomous Robot for Underwater Intervention Tasks Successfully Tested

The test was performed a few weeks ago at the Universitat de Girona, where there is a pool suitable for experimentation on underwater robotics. During the meeting, the researchers also tested the performance of the three parts involved in the experiment: the robotic arm, which is being improved by the UJI; the vehicle, in which the Universitat de Girona is working, and the computer vision techniques, which are being developed by the Universitat de les Illes Balears.

In the first part of the experiment the vehicle in which the robot was anchored descended to the bottom of the pool to survey the area using computer vision techniques and to draw a map. After that, the researchers asked the robot to recover an object (a black box), and the vehicle with the robotic arm plunged again, sought the object with the required characteristics, picked it up and pulled it to the surface.

The research group Interactive and Robotics Systems (IRS Lab) is composed by Prats, Juan Carlos García, José Javier Fernández and Raúl Marín and is led by Pedro Sanz. The team obtained the first results of manipulation underwater just two weeks ago, playing grip simulations with the robotic arm in a water tank installed in an office at the UJI before going to Girona to make the joint integration testing. The arm has four articulations, two at the shoulders, one at the elbow and the fourth at the wrist. It can also open its hand, which is claw-like but has T-shaped slots that enable to anchor on it cables or tools for picking up objects.

Achieving such a project would reduce the economic and human resources efforts which are attached to submarine operations, since support vessels or umbilical cables would not be necessary, nor ROV pilots responsible for teleoperation in conditions that involve fatigue and stress. Thus, this point would enable to carry out operations which would be impossible for teleoperated systems and which require a continuous connection through an umbilical cable to a support ship, a characteristic that affects the vehicle dynamics and limits the travel distance of the robot.

At present, the first application which more than 40 researchers are seeking is the recovery of black boxes with this autonomous action system, but some other potential application scenarios that could benefit from this project would be certain tasks associated with marine biology, performing routine practices such as taking samples (eg rock, water or sand); at permanent observatories, in lifesaving, in health care tasks to the diving teams such as lighting in a particular area, or assistance in the use of some kind of tool, to name only a few examples.

The project is funded with 530 000 euros by the Spanish Ministry of Science and Innovation, within the VI National Plan for Scientific Research, Development and Technological Innovation 2008-2011. Each one of the participating universities is responsible for a specific subproject. The UJI is the responsible for the mechanical integration of the robotic arm, the visual tracking of the object of interest, the control of the arm for handling tasks and the interface to specify these tasks.

The Universitat de Girona is the responsible for generating the navigation and mechatronics systems of the underwater vehicle where the robot is docked. The Universitat de les Illes Balears is the responsible for assisting in the planning and guiding of the movements necessary to achieve the autonomous navigation of the robot, using advanced computer vision techniques.

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Artificial Tissue Promotes Skin Growth in Wounds

These so-called dermal templates were engineered in the lab of Abraham Stroock, associate professor of chemical and biomolecular engineering at Cornell and member of the Kavli Institute at Cornell for Nanoscale Science, in collaboration with Dr. Jason A. Spector, assistant professor of surgery at Weill Cornell Medical College, and an interdisciplinary team of Ithaca and Weill scientists. The research was published online May 6 in the journalBiomaterials.

The biomaterials are composed of experimental tissue scaffolds that are about the size of a dime and have the consistency of tofu. They are made of a material called type 1 collagen, which is a well-regulated biomaterial used often in surgeries and other biomedical applications. The templates were fabricated with tools at the Cornell NanoScale Science and Technology Facility to contain networks of microchannels that promote and direct growth of healthy tissue into wound sites.

"The challenge was how to promote vascular growth and to keep this newly forming tissue alive and healthy as it heals and becomes integrated into the host," Stroock said.

The grafts promote the ingrowth of a vascular system -- the network of vessels that carry blood and circulate fluid through the body -- to the wounded area by providing a template for growth of both the tissue (dermis, the deepest layer of skin), and the vessels. Type I collagen is biocompatible and contains no living cells itself, reducing concerns about immune system response and rejection of the template.

A key finding of the study is that the healing process responds strongly to the geometry of the microchannels within the collagen. Healthy tissue and vessels can be guided to grow toward the wound in an organized and rapid manner.

Dermal templates are not new; the Johnson& Johnson product Integra, for example, is widely used for burns and other deep wounds, Spector said, but it falls short in its ability to encourage growth of healthy tissue because it lacks the microchannels designed by the Cornell researchers.

"They can take a long time to incorporate into the person you're putting them in," Spector said."When you're putting a piece of material on a patient and the wound is acellular, it has a big risk for infection and requires lots of dressing changes and care. Ideally you want to have a product or material that gets vascularized very rapidly."

In the clinic, Spector continued, patients often need significant reconstructive surgery to repair injuries with exposed vital structures like bone, tendon or orthopedic hardware. The experimental templates are specifically designed to improve vascularization over these"barren" areas, perhaps one day eliminating the need for such invasive surgeries and reducing the patient's discomfort and healing time.

Eventually, the scientists may try to improve their tissue grafts by, for example, reinforcing them with polymer meshes that could also act as a wound covering, Spector said.

Other collaborators include first author Ying Zheng, a former postdoctoral associate in Stroock's lab; Dr. Peter W. Henderson, chief research fellow at Weill Cornell's Laboratory for Bioregenerative Medicine and Surgery; graduate student Nak Won Choi; and Lawrence J. Bonassar, associate professor of biomedical engineering.

The work was supported by the Morgan Fund for Tissue Engineering and the New York State Office of Science, Technology and Academic Research.

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Autonomous Robots Made to Explore and Map Buildings

This isn't a future-tech scenario. This advanced autonomous capability has been developed by a team from the Georgia Institute of Technology, the University of Pennsylvania and the California Institute of Technology/Jet Propulsion Laboratory (JPL). A paper describing this capability and its present level of performance was presented in April at the SPIE Defense, Security and Sensing Conference in Orlando, Fla.

"When first responders -- whether it's a firefighter in downtown Atlanta or a soldier overseas -- confront an unfamiliar structure, it's very stressful and potentially dangerous because they have limited knowledge of what they're dealing with," said Henrik Christensen, a team member who is a professor in the Georgia Tech College of Computing and director of the Robotics and Intelligent Machines Center there."If those first responders could send in robots that would quickly search the structure and send back a map, they'd have a much better sense of what to expect and they'd feel more confident."

The ability to map and explore simultaneously represents a milestone in the Micro Autonomous Systems and Technology (MAST) Collaborative Technology Alliance Program, a major research initiative sponsored by the U.S. Army Research Laboratory. The five-year program is led by BAE Systems and includes numerous principal and general members comprised largely of universities.

MAST's ultimate objective is to develop technologies that will enable palm-sized autonomous robots to help humans deal with civilian and military challenges in confined spaces. The program vision is for collaborative teams of tiny devices that could roll, hop, crawl or fly just about anywhere, carrying sensors that detect and send back information critical to human operators.

The wheeled platforms used in this experiment measure about one foot square. But MAST researchers are working toward platforms small enough to be held in the palm of one hand. Fully autonomous and collaborative, these tiny robots could swarm by the scores into hazardous situations.

The MAST program involves four principal research teams: integration, microelectronics, microsystems mechanics, and processing for autonomous operation. Georgia Tech researchers are participating in every area except microelectronics. In addition to the College of Computing, researchers from the Georgia Tech Research Institute (GTRI), the School of Aerospace Engineering and the School of Physics are involved in MAST work.

The experiment -- developed by the Georgia Tech MAST processing team -- combines navigation technology developed by Georgia Tech with vision-based techniques from JPL and network technology from the University of Pennsylvania.

In addition to Christensen, members of the Georgia Tech processing team involved in the demonstration include Professor Frank Dellaert of the College of Computing and graduate students Alex Cunningham, Manohar Paluri and John G. Rogers III. Regents professor Ronald C. Arkin of the College of Computing and Tom Collins of GTRI are also members of the Georgia Tech processing team.

In the experiment, the robots perform their mapping work using two types of sensors -- a video camera and a laser scanner. Supported by onboard computing capability, the camera locates doorways and windows, while the scanner measures walls. In addition, an inertial measurement unit helps stabilize the robot and provides information about its movement.

Data from the sensors are integrated into a local area map that is developed by each robot using a graph-based technique called simultaneous localization and mapping (SLAM). The SLAM approach allows an autonomous vehicle to develop a map of either known or unknown environments, while also monitoring and reporting on its own current location.

SLAM's flexibility is especially valuable in areas where global positioning system (GPS) service is blocked, such as inside buildings and in some combat zones, Christensen said. When GPS is active, human handlers can use it to see where their robots are. But in the absence of global location information, SLAM enables the robots to keep track of their own locations as they move.

"There is no lead robot, yet each unit is capable of recruiting other units to make sure the entire area is explored," Christensen explained."When the first robot comes to an intersection, it says to a second robot, 'I'm going to go to the left if you go to the right.'"

Christensen expects the robots' abilities to expand beyond mapping soon. One capability under development by a MAST team involves tiny radar units that could see through walls and detect objects -- or humans -- behind them. Infrared sensors could also support the search mission by locating anything giving off heat. In addition, a MAST team is developing a highly flexible"whisker" to sense the proximity of walls, even in the dark.

The processing team is designing a more complex experiment for the coming year to include small autonomous aerial platforms for locating a particular building, finding likely entry points and then calling in robotic mapping teams. Demonstrating such a capability next year would culminate progress in small-scale autonomy during MAST's first five years, Christensen said.

In addition to the three universities, other MAST team participants are North Carolina A&T State University, the University of California Berkeley, the University of Maryland, the University of Michigan, the University of New Mexico, Harvard University, the Massachusetts Institute of Technology, and two companies: BAE Systems and Daedalus Flight Systems.

Research was sponsored by the Army Research Laboratory under Cooperative Agreement Number W911NF-08-2-0004.

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New Calculations on Blackbody Energy Set the Stage for Clocks With Unprecedented Accuracy

Precision timekeeping is one of the bedrock technologies of modern science and technology. It underpins precise navigation on Earth and in deep space, synchronization of broadband data streams, precision measurements of motion, forces and fields, and tests of the constancy of the laws of nature over time.

"Using our calculations, researchers can account for a subtle effect that is one of the largest contributors to error in modern atomic timekeeping," says lead author Marianna Safronova of the University of Delaware, the first author of the presentation."We hope that our work will further improve upon what is already the most accurate measurement in science: the frequency of the aluminum quantum-logic clock," adds co-author Charles Clark, a physicist at the Joint Quantum Institute, a collaboration of the National Institute of Standards and Technology (NIST) and the University of Maryland.

The paper was presented at the 2011 Conference on Lasers and Electro-Optics in Baltimore, Md.

The team studied an effect that is familiar to anyone who has basked in the warmth of a campfire: heat radiation. Any object at any temperature, whether the walls of a room, a person, the Sun or a hypothetical perfect radiant heat source known as a"black body," emits heat radiation. Even a completely isolated atom senses the temperature of its environment. Just as heat swells the air in a hot-air balloon, so-called"blackbody radiation" (BBR) enlarges the size of the electron clouds within the atom, though to a much lesser degree -- by one part in a hundred trillion, a size that poses a severe challenge to precision measurement.

This effect comes into play in the world's most precise atomic clock, recently built by NIST researchers. This quantum-logic clock, based on atomic energy levels in the aluminum ion, Al+, has an uncertainty of 1 second per 3.7 billion years, translating to 1 part in 8.6 x 10-18, due to a number of small effects that shift the actual tick rate of the clock.

To correct for the BBR shift, the team used the quantum theory of atomic structure to calculate the BBR shift of the atomic energy levels of the aluminum ion. To gain confidence in their method, they successfully reproduced the energy levels of the aluminum ion, and also compared their results against a predicted BBR shift in a strontium ion clock recently built in the United Kingdom. Their calculation reduces the relative uncertainty due to room-temperature BBR in the aluminum ion to 4 x 10^-19, or better than 18 decimal places, and a factor of 7 better than previous BBR calculations.

Current aluminum-ion clocks have larger sources of uncertainty than the BBR effect, but next-generation aluminum clocks are expected to greatly reduce those larger uncertainties and benefit substantially from better knowledge of the BBR shift.

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Developing Advanced Biofuels: Researchers Counteract Biofuel Toxicity in Microbes

Researchers at the U.S. Department of Energy (DOE)'s Joint BioEnergy Institute (JBEI) have provided a solution to this problem by developing a library of microbial efflux pumps that were shown to significantly reduce the toxicity of seven representative biofuels in engineered strains of Escherichia coli.

"Working with all available microbial genome sequence data, we generated a library of largely uncharacterized genes and were able to devise a simple but highly effective strategy to identify efflux pumps that could alleviate biofuel toxicity in E. coli and, as a consequence, help improve biofuel production," says Aindrila Mukhopadhyay, a chemist with JBEI's Fuels Synthesis Division, who led this research.

Mukhopadhyay, who also holds an appointment with the Lawrence Berkeley National Laboratory (Berkeley Lab)'s Physical Biosciences Division, is the corresponding author on a paper published in the journalMolecular Systems Biology. Co-authoring the paper with Mukhopadhyay were Mary Dunlop, Zain Dossani, Heather Szmidt, Hou-Cheng Chu, Taek Soon Lee, Jay Keasling and Masood Hadi.

Research efforts are underway at JBEI and elsewhere to engineer microorganisms, such as E. coli, to produce advanced biofuels in a cost effective manner. These fuels, which encompass short-to-medium carbon-chain alcohols, such as butanol, isopentanol and geraniol, can replace gasoline on a gallon-for-gallon basis and be used in today's infrastructures and engines, unlike ethanol. Biofuels made from branched carbon-chain compounds, such as geranyl acetate and farnesyl hexanoate, would also be superior to today's biodiesel, which is made from esters of linear fatty acids. Cyclic alkenes, such as limonene and pinene, could serve as precursors to jet fuel. Although biosynthetic pathways to the production of these carbon compounds in microbes have been identified, product toxicity to microbes is a common problem in strain engineering for biofuels and other biotechnology applications.

"In order for microbial biofuel production to be cost effective, yields must exceed native microbial tolerance levels, necessitating the development of stress-tolerant microbe strains," Mukhopadhyay says."It is crucial that we improve tolerance in parallel with the development of metabolic pathways for the production of next-generation biofuels."

Microbes employ various strategies for addressing cell toxicity but perhaps the most effective are efflux pumps, proteins in the cytoplasmic membrane of cells whose function is to transport toxic substances out of the cell. This is done actively, using proton motive force. However, to date very few of these have been characterized for efficacy against biofuel like compounds.

"Sequenced bacterial genomes include many efflux pumps but remain a largely unexplored resource for use in engineering fuel tolerance," Mukhopadhyay says."We took a systematic approach to screen a library of primarily uncharacterized heterologous pumps for engineering biofuel tolerant host strains. We were then able to demonstrate that expression of a heterologous pump can increase the yield of a biofuel in the production strain."

Since all known solvent-resistant efflux pumps in Gram-negative bacteria fall into the hydrophobe/amphiphile efflux (HAE1) family, Mukhopadhyay and her colleagues constructed a datab

ase of all HAE1 pumps from sequenced bacterial genomes. They then performed a bioinformatics screen to compare regions predicted to be responsible for substrate specificity to those of TtgB, a well-characterized solvent-resistant efflux pump.

"This metric allowed us to rank the complete set of pumps and select a subset that represented a uniform distribution of candidate genes," says Mukhopadhyay."To construct the library, we amplified efflux pump operons from the genomic DNA of the selected bacteria, cloned them into a vector, and transformed the vector into an E. coli host strain."

In a series of survival competitions, the two microbial efflux pumps that performed best were the native E. coli pump AcrAB and a previously uncharacterized pump from a marine microbe Alcanivorax borkumensis.

"We focused on the A. borkumensis pump and tested it in a strain of host microbe engineered to produce the limonene jet fuel precursor," Mukhopadhyay says."Microbes expressing the pump produced significantly more limonene than those with no pump, providing an important proof of principle demonstration that efflux pumps that increase tolerance to exogenous biofuel can also improve the yield of a production host."

Mukhopadhyay and her JBEI colleagues have begun evaluating microbial efflux pumps for other important compounds as well as inhibitors present in the carbon source from lignocellulose. They are also looking to improve the A. borkumensis pump and other high performers in their current library, and to optimize the systems by which pump genes are expressed in engineered biofuel-producing microbial strains.

"We believe our bioprospecting strategy for biofuel tolerance mechanisms is going to be a valuable and widely applicable tool in the biotechnology field for engineering new microbial production strains," Mukhopadhyay says.

This research was supported by JBEI through the DOE Office of Science.

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Controling Robotic Arms Is Child's Play

"The input device contains various movement sensors, also called inertial sensors," says Bernhard Kleiner of the Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart, who leads the project. The individual micro-electromechanical systems themselves are not expensive. What the scientists have spent time developing is how these sensors interact."We have developed special algorithms that fuse the data of individual sensors and identify a pattern of movement. That means we can detect movements in free space," summarizes Kleiner.

What may at first appear to be a trade show gimmick, is in fact a technology that offers numerous advantages in industrial production and logistical processes. The system could be used to simplify the programming of industrial robots, for example. To date, this has been done with the aid of laser tracking systems: An employee demonstrates the desired motion with a hand-held baton that features a white marker point. The system records this motion by analyzing the light reflected from a laser beam aimed at the marker. Configuring and calibrating the system takes a lot of time. The new input device should eliminate the need for these steps in the future -- instead, employees need only pick up the device and show the robot what it is supposed to do.

The system has numerous applications in medicine, as well. Take, for example, gait analysis. Until now, cameras have made precise recordings of patients as they walk back and forth along a specified path. The films reveal to the physician such things as how the joints behave while walking, or whether incorrect posture in the knees has been improved by physical therapy. Installing the cameras, however, is complex and costly, and patients are restricted to a predetermined path. The new sensor system can simplify this procedure: Attached to the patient's upper thigh, it measures the sequences and patterns of movement -- without limiting the patient's motion in any way.

"With the inertial sensor system, gait analysis can be performed without a frame of reference and with no need for a complex camera system," explains Kleiner. In another project, scientists are already working on comparisons of patients' gait patterns with those patterns appearing in connection with such diseases as Parkinson's.

Another medical application for the new technology is the control of active prostheses containing numerous small actuators. Whenever the patient moves, the prosthesis in turn also moves; this makes it possible for a leg prosthesis to roll the foot while walking. Here, too, the sensor could be attached to the patient's upper thigh and could analyze the movement, helping to regulate the motors of the prosthesis. Research scientists are currently working on combining the inertial sensor system with an electromyographic (EMG) sensor. Electromyography is based on the principle that when a muscle tenses, it produces an electrical voltage which a sensor can then measure by way of an electrode. If the sensor is placed, for example, on the muscle responsible for lifting the patient's foot, the sensor registers when the patient tenses this muscle -- and the prosthetic foot lifts itself. EMG sensors like this are already available but are difficult to position.

"While standard EMG sensors consist of individual electrodes that have to be positioned precisely on the muscle, our system is made up of many small electrodes that attach to a surface area. This enables us to sense muscle movements much more reliably," says Kleiner.

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