During his May 18 University of Pennsylvania Commencement Address, Eric Schmidt, Google Chairman and Chief Executive Officer, stressed that downturns can lead to innovation and playfully compared his generation with his more tech-savvy audience.
They’ve made electronics that can bend. They’ve made electronics that can stretch. And now, they’ve reached the ultimate goal: electronics that can be subjected to any complex deformation, including twisting.
Yonggang Huang, Joseph Cummings Professor of Civil and Environmental Engineering and Mechanical Engineering at Northwestern University’s McCormick School of Engineering and Applied Science, and John Rogers, the Flory-Founder Chair Professor of Materials Science and Engineering at the University of Illinois at Urbana-Champaign, have improved their so-called “pop-up” technology to create circuits that can be twisted. Such electronics could be used in places where flat, unbending electronics would fail, like on the human body.
Electronic components historically have been flat and unbendable because silicon, the principal component of all electronics, is brittle and inflexible. Any significant bending or stretching renders an electronic device useless.
Huang and Rogers developed a method to fabricate stretchable electronics that increases the stretching range (as much as 140%) and allows the user to subject circuits to extreme twisting. This emerging technology promises new flexible sensors, transmitters, photovoltaic and microfluidic devices, and other applications for medical and athletic use.
The partnership—where Huang focuses on theory and Rogers focuses on experiments—has been fruitful for the past several years. Back in 2005, the pair developed a one-dimensional, stretchable form of single-crystal silicon that could be stretched in one direction without altering its electrical properties.
Next, the researchers developed a new kind of technology that allowed circuits to be placed on a curved surface. That technology used an array of circuit elements approximately 100 micrometers squared that were connected by metal “pop-up bridges.”
The circuit elements were so small that when placed on a curved surface, they didn’t bend, similar to how buildings don’t bend on the curved Earth. The system worked because these elements were connected by metal wires that popped up when bent or stretched.
In the research reported in Proceedings of the National Academy of Sciences (PNAS), Huang and Rogers took their pop-up bridges and made them into an “S” shape, which, in addition to bending and stretching, have enough give that they can be twisted as well. “For a lot of applications related to the human body—like placing a sensor on the body—an electronic device needs not only to bend and stretch but also to twist,” says Huang. “So we improved our pop-up technology to accommodate this. Now it can accommodate any deformation.
Twenty young scientists from among those taking part in the National Science Foundation’s (NSF) Faculty Early Career Development Program (CAREER) recently received an additional distinction as winners of the Presidential Early Career Awards for Scientists and Engineers (PECASE) for the 2007 competition.
The PECASE program recognizes outstanding scientists and engineers who, early in their careers, show exceptional potential for leadership at the frontiers of knowledge. This Presidential Award is the highest honor bestowed by the U.S. government on scientists and engineers beginning their independent careers. In addition to the NSF’s winners, there are 48 scientists nominated by other government agencies.
By receiving awards through the CAREER program, the PECASE winners had already demonstrated their success in integrating research and education within the context of the mission of their organization.
“We take great pride in the PECASE winners,” says Kathie L. Olsen, NSF’s deputy director. “It is important to support the transformational research of these beginning scientists, and to foster their work in educational outreach and mentoring.”
Recent simulated earthquake tests conducted by University of California, San Diego engineers are expected to lead to retrofit schemes that make historic buildings safer. The structural engineers tested a structure similar to those that were built in California in the 1920s that have masonry infilled walls and reinforced concrete frames. Based on data collected from tests performed on the world’s only outdoor shake table, the engineers will come up with new seismic assessment tools and critical retrofit designs for these kinds of structures, which were not designed according to current standards. As part of the project, the engineers subjected a Three-story structure with non-ductile reinforced concrete frames with unreinforced masonry infilled walls to shaking representative of a series of different seismic events.
Infill walls can generally improve the seismic safety of a building up to a certain level of earthquake intensity depending on the number of walls present and their locations. Once the earthquake force exceeds the strength of the walls, the failure of such structures could be sudden and catastrophic as demonstrated in the recent UC San Diego tests. Due to the frame-panel interaction, the earthquake load resisting mechanism of these structures is complicated, and it is difficult for engineers to assess their seismic resistance. The objectives of this project are to investigate the resistance of this type of structure under realistic seismic load conditions with large-scale tests and develop and calibrate reliable analytical models to assess their seismic performance.
“We will also look into retrofit methods to push the performance envelope of these structures. In reality, some of these structures may not have sufficient walls to resist earthquake loads or some walls may be missing in critical locations of a building. Hence, we need reliable means to assess and improve their performance,” says Benson Shing, a structural engineering professor at the UC San Diego Jacobs School of Engineering, and the lead researcher on the project.
Currently, there is a lack of reliable analysis methods to evaluate the seismic performance of these older structures and validated retrofit methods to improve their seismic behavior. In California, construction of unreinforced masonry buildings including those with brick infill walls came to a halt after the 1933 Long Beach earthquake, which was a 6.4 magnitude, but many of them still exist today. Although only moderate in terms of magnitude, this earthquake caused serious damage to unreinforced masonry structures on land fill from Los Angeles to Laguna Beach. Property damage was estimated at $40 million, and 115 people were killed.
The impact of this $1.24 million project, funded by the National Science Foundation, is vast since a large number of such structures can be found in the Pacific Northwest, and in the Midwestern and Eastern United States, where big earthquakes could occur even though the recurrence frequency is lower. This type of structural system is also very common in areas of high seismicity around the world, including China and the Mediterranean region.
Comments Off on Harnessing Light to Drive Nanomachines
Science fiction writers have long envisioned sailing a spacecraft by the optical force of the sun’s light. But, the forces of sunlight are too weak to fill even the oversized sails that have been tried. Now a team led by researchers at the Yale School of Engineering & Applied Science has shown that the force of light indeed can be harnessed to drive machines—when the process is scaled to nano-proportions.
Their work opens the door to a new class of semiconductor devices that are operated by the force of light. They envision a future where this process powers quantum information processing and sensing devices, as well as telecommunications that run at ultra-high speeds and consume little power.
The research demonstrates a marriage of two emerging fields of research, nanophotonics and nanomechanics, which makes possible the extreme miniaturization of optics and mechanics on a silicon chip.
The energy of light has been harnessed and used in many ways. The force of light is different—it is a push or a pull action that causes something to move.
“While the force of light is far too weak for us to feel in everyday life, we have found that it can be harnessed and used at the nanoscale,” says team leader Hong Tang, assistant professor at Yale. “Our work demonstrates the advantage of using nano-objects as ‘targets’ for the force of light—using devices that are a billion-billion times smaller than a space sail, and that match the size of today’s typical transistors.”
Until now, light has only been used to maneuver single tiny objects with a focused laser beam, a technique called “optical tweezers.” Postdoctoral scientist and lead author, Mo Li notes, “Instead of moving particles with light, now we integrate everything on a chip and move a semiconductor device.”
“When researchers talk about optical forces, they are generally referring to the radiation pressure light applies in the direction of the flow of light,” states Tang. “The new force we have investigated actually kicks out to the side of that light flow.”
While this new optical force was predicted by several theories, the proof required state-of-the-art nanophotonics to confine light with ultra-high intensity within nanoscale photonic wires. The researchers showed that when the concentrated light was guided through a nanoscale mechanical device, significant light force could be generated—enough, in fact, to operate nanoscale machinery on a silicon chip.
The light force was routed in much the same way electronic wires are laid out on today’s large-scale integrated circuits. Because light intensity is much higher when it is guided at the nanoscale, they were able to exploit the force. “We calculate that the illumination we harness is a million times stronger than direct sunlight,” adds Wolfram Pernice, a Humboldt postdoctoral fellow with Tang.
“We create hundreds of devices on a single chip, and all of them work,” says Tang, who attributes this success to a great optical I/O device design provided by their collaborators at the University of Washington.
It took more than 60 years to progress from the first transistors to the speed and power of today’s computers. Creating devices that run solely on light rather than electronics will now begin a similar process of development, according to the authors.
“While this development has brought us a new device concept and a giant step forward in speed, the next developments will be in improving the mechanical aspects of the system. But,” says Tang, “the photon force is with us.”
Engineers at Ohio State University are developing a computerized surveillance system that, when completed, will attempt to recognize whether a person on the street is acting suspiciously or appears to be lost.
Intelligent video cameras, large video screens, and geo-referencing software are among the technologies that will soon be available to law enforcement and security agencies.
In the recent proceedings of the 2008 IEEE Conference on Advanced Video and Signal Based Surveillance, James W. Davis and doctoral student Karthik Sankaranarayanan reported that they’ve completed the first three phases of the project: they have one software algorithm that creates a wide-angle video panorama of a street scene, another that maps the panorama onto a high-resolution aerial image of the scene, and a method for actively tracking a selected target.
The ultimate goal is a networked system of “smart” video cameras that will let surveillance officers observe a wide area quickly and efficiently. Computers will carry much of the workload.
“In my lab, we’ve always tried to develop technologies that would improve officers’ situational awareness, and now we want to give that same kind of awareness to computers,” says Davis, an associate professor of computer science and engineering at Ohio State University. The research isn’t meant to gather specific information about individuals, he explains.
“In our research, we care what you do, not who you are. We aim to analyze and model the behavior patterns of people and vehicles moving through the scene, rather than attempting to determine the identity of people. We are trying to automatically learn what typical activity patterns exist in the monitored area, and then have the system look for atypical patterns that may signal a person of interest—perhaps someone engaging in nefarious behavior or a person in need of help.” The first piece of software expands the small field of view that traditional pan-tilt-zoom security cameras offer.
The system won’t rely on traditional profiling methods, he says. A person’s race or sex or general appearance won’t matter. What will matter is where the person goes, and what they do. “If you’re doing something strange, we want to be able to detect that and figure out what’s going on.”
They are now looking into the possibility of deploying a large test system around the state of Ohio using their research. Here, law enforcement could link video cameras around the major cities, map video panoramas to publicly available aerial maps (such as those maintained by the Ohio Geographically Referenced Information Program), and use their software to provide a higher level of “location awareness” for surveillance.