Jorgensen Laboratory Awarded LEED Platinum Certification

The recent renovations of the Jorgensen Laboratory included many upgrades that were designed to reflect Caltech's commitment to sustainability. Now the building has achieved LEED Platinum certification, the highest honor of the U.S. Green Building Council.

"Achieving Platinum certification on this building was particularly rewarding given the fact that the building will serve as a studio for sustainable energy research," says John Onderdonk, director of sustainability programs at Caltech.

LEED—Leadership in Energy and Environmental Design—is a voluntary program that provides verification of green building design through a survey of prerequisites and guideline credits. To obtain LEED certification, a building must earn a minimum of 40 points on a 110-point LEED rating system scale. Jorgensen received 87 points—80 is the minimum needed for Platinum certification—for its conservation features, which include a "green" roof, natural ventilation systems, use of on-campus solar photovoltaic power, and low-flow water fixtures, among other environmentally conscious details.

Jorgensen is one of 20 LEED Platinum-certified higher-education lab buildings in the country, and one of seven in the state. It is the second higher-education lab building in the state to receive LEED Platinum certification under the current rating system. Caltech's renovation of the Linde + Robinson Lab also received LEED Platinum status last year.

The Jorgensen Lab officially opened in October 2012 and houses scientists who are focused on clean-energy research

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Notes from the Back Row: "Engineering with Impact"

If you hit something hard enough, it will break, and the consequences can be catastrophic. A space rock roughly the size of Pasadena killed the dinosaurs when it hit the Earth at about 45,000 miles per hour, but even something as small as a bird hitting a turbine blade can bring down an airplane. The damage occurs in the blink of an eye as unimaginable pressures are fleetingly focused on the hapless chunk of rock or metal. The key to survival is to disperse those forces. But how? Caltech professor Ravi Ravichandran is trying to find out.

Guruswami "Ravi" Ravichandran is the John E. Goode, Jr., Professor of Aerospace and professor of mechanical engineering and the director of the Graduate Aerospace Laboratories at Caltech. His PhD thesis on the fracture dynamics of metals under extreme impacts, written at Brown University in 1986, remains one of the classic papers in the field.

At Caltech, Ravichandran studies impacts that pack a wallop of up to a million times the pressure of Earth's atmosphere. Such extreme pressures are actually quite mundane: a head-on collision at 65 miles per hour exerts a force of some 7,000 atmospheres during the millisecond that the vehicles' steel frames buckle. (By contrast, the pressure at the bottom of the Mariana Trench in the western Pacific, the deepest point in the world's oceans, is a mere 1,000 atmospheres.) In a typical experiment, a reconditioned naval gun from World War II shoots an aluminum projectile at a copper plate, compressing it by as much as 30 percent for a millionth of a second. Meanwhile, a laser "camera" records the ripples created by the projectile's kinetic energy as it turns into pressure waves within the copper plate.

The best way we know to dissipate these waves is to pass them through alternating layers of very stiff and very elastic materials. This is the principle behind body armor and bulletproof glass, as Ravichandran vividly demonstrated during his talk by showing a video clip produced by an armored-car company. In the clip, the company's CEO stood behind a bulletproof windshield while his assistant peppered it with three rounds from an AK-47. Spiderwebs of cracks formed in the inner layer of glass and license-plate-sized fragments of the outer layer were blasted free, but the layer of polymer sandwiched between the glass sheets stopped the slugs. If one layer of elastic is good, more layers should be even better. The logical extreme—an infinite number of layers—presents certain manufacturing challenges, so "we're extending this idea of layered media into particulate composites in order to make realistic engineering materials for shock-protection applications," Ravichandran says. Think high-tech sandbags, in other words.  

"Engineering with Impact" is available for download in HD from Caltech on iTunesU. (Episode 13)

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TEDxCaltech: Advancing Humanoid Robots

This week we will be highlighting the student speakers who auditioned and were selected to give five-minute talks about their brain-related research at TEDxCaltech: The Brain, a special event that will take place on Friday, January 18, in Beckman Auditorium. 

In the spirit of ideas worth spreading, TED has created a program of local, self-organized events called TEDx. Speakers are asked to give the talk of their lives. Live video coverage of the TEDxCaltech experience will be available during the event at http://tedxcaltech.caltech.edu.

When Matanya Horowitz started his undergraduate work in 2006 at University of Colorado at Boulder, he knew that he wanted to work in robotics—mostly because he was disappointed that technology had not yet made good on his sci-fi–inspired dreams of humanoid robots.

"The best thing we had at the time was the Roomba, which is a great product, but compared to science fiction it seemed really diminutive," says Horowitz. He therefore decided to major in not just electrical engineering, but also economics, applied math, and computer science. "I thought that the answer to better robots would lie somewhere in the middle of these different subjects, and that maybe each one held a different key," he explains.

Now a doctoral student at Caltech—he earned his masters in the same four years as his multiple undergrad degrees—Horowitz is putting his range of academic experience to work in the labs of engineers Joel Burdick and John Doyle to help advance robotics and intelligent systems. As a member of the control and dynamical systems group, he is active in several Defense Advanced Research Projects Agency (DARPA) challenges that seek to develop better control mechanisms for robotic arms, as well as develop humanoid robots that can do human-like tasks in dangerous situations, such as disable bombs or enter nuclear power plants during an emergency. 

But beneficial advances in robotics also bring challenges. Inspired as a kid by the robot tales of Isaac Asimov, Horowitz has long been interested in how society might be affected by robots.

"As I began programming just on my own, I saw how easy it was to create something that at least seemed to act with intelligence," he says. "It was interesting to me that we were so close to humanoid robots and that doing these things was so easy. But we also have all these implications we need to think about."

Horowitz's TEDx talk will explore some of the challenges of building and controlling something that needs to interact in the physical world. He says he's thrilled to have the opportunity to speak at TEDx, not just for the chance to talk to a general audience about his work, but also to hopefully inspire others by his enthusiasm for the field.

"Recently, there has been such a monumental shift from what robots were capable of even just five years ago, and people should be really excited about this," says Horowitz. "We've been hearing about robots for 30, 40 years—they've always been 'right around the corner.' But now we can finally point to one and say, 'Here it is, literally coming around a corner.'"

 

 

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Friday, January 25, 2013
Annenberg 121

Course Ombudspeople Lunch

Faulty Behavior

New earthquake fault models show that "stable" zones may contribute to the generation of massive earthquakes

PASADENA, Calif.—In an earthquake, ground motion is the result of waves emitted when the two sides of a fault move—or slip—rapidly past each other, with an average relative speed of about three feet per second. Not all fault segments move so quickly, however—some slip slowly, through a process called creep, and are considered to be "stable," or not capable of hosting rapid earthquake-producing slip.  One common hypothesis suggests that such creeping fault behavior is persistent over time, with currently stable segments acting as barriers to fast-slipping, shake-producing earthquake ruptures. But a new study by researchers at the California Institute of Technology (Caltech) and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) shows that this might not be true.

"What we have found, based on laboratory data about rock behavior, is that such supposedly stable segments can behave differently when an earthquake rupture penetrates into them. Instead of arresting the rupture as expected, they can actually join in and hence make earthquakes much larger than anticipated," says Nadia Lapusta, professor of mechanical engineering and geophysics at Caltech and coauthor of the study, published January 9 in the journal Nature.

She and her coauthor, Hiroyuki Noda, a scientist at JAMSTEC and previously a postdoctoral scholar at Caltech, hypothesize that this is what occurred in the 2011 magnitude 9.0 Tohoku-Oki earthquake, which was unexpectedly large.

Fault slip, whether fast or slow, results from the interaction between the stresses acting on the fault and friction, or the fault's resistance to slip. Both the local stress and the resistance to slip depend on a number of factors such as the behavior of fluids permeating the rocks in the earth's crust. So, the research team formulated fault models that incorporate laboratory-based knowledge of complex friction laws and fluid behavior, and developed computational procedures that allow the scientists to numerically simulate how those model faults will behave under stress.

"The uniqueness of our approach is that we aim to reproduce the entire range of observed fault behaviors—earthquake nucleation, dynamic rupture, postseismic slip, interseismic deformation, patterns of large earthquakes—within the same physical model; other approaches typically focus only on some of these phenomena," says Lapusta.

In addition to reproducing a range of behaviors in one model, the team also assigned realistic fault properties to the model faults, based on previous laboratory experiments on rock materials from an actual fault zone—the site of the well-studied 1999 magnitude 7.6 Chi-Chi earthquake in Taiwan.

"In that experimental work, rock materials from boreholes cutting through two different parts of the fault were studied, and their properties were found to be conceptually different," says Lapusta. "One of them had so-called velocity-weakening friction properties, characteristic of earthquake-producing fault segments, and the other one had velocity-strengthening friction, the kind that tends to produce stable creeping behavior under tectonic loading. However, these 'stable' samples were found to be much more susceptible to dynamic weakening during rapid earthquake-type motions, due to shear heating."

Lapusta and Noda used their modeling techniques to explore the consequences of having two fault segments with such lab-determined fault-property combinations. They found that the ostensibly stable area would indeed occasionally creep, and often stop seismic events, but not always. From time to time, dynamic rupture would penetrate that area in just the right way to activate dynamic weakening, resulting in massive slip. They believe that this is what happened in the Chi-Chi earthquake; indeed, the quake's largest slip occurred in what was believed to be the "stable" zone.

"We find that the model qualitatively reproduces the behavior of the 2011 magnitude 9.0 Tohoku-Oki earthquake as well, with the largest slip occurring in a place that may have been creeping before the event," says Lapusta. "All of this suggests that the underlying physical model, although based on lab measurements from a different fault, may be qualitatively valid for the area of the great Tohoku-Oki earthquake, giving us a glimpse into the mechanics and physics of that extraordinary event."

If creeping segments can participate in large earthquakes, it would mean that much larger events than seismologists currently anticipate in many areas of the world are possible. That means, Lapusta says, that the seismic hazard in those areas may need to be reevaluated.

For example, a creeping segment separates the southern and northern parts of California's San Andreas Fault. Seismic hazard assessments assume that this segment would stop an earthquake from propagating from one region to the other, limiting the scope of a San Andreas quake. However, the team's findings imply that a much larger event may be possible than is now anticipated—one that might involve both the Los Angeles and San Francisco metropolitan areas.

"Lapusta and Noda's realistic earthquake fault models are critical to our understanding of earthquakes—knowledge that is essential to reducing the potential catastrophic consequences of seismic hazards," says Ares Rosakis, chair of Caltech's division of engineering and applied science. "This work beautifully illustrates the way that fundamental, interdisciplinary research in the mechanics of seismology at Caltech is having a positive impact on society."

Now that they've been proven to qualitatively reproduce the behavior of the Tohoku-Oki quake, the models may be useful for exploring future earthquake scenarios in a given region, "including extreme events," says Lapusta. Such realistic fault models, she adds, may also be used to study how earthquakes may be affected by additional factors such as man-made disturbances resulting from geothermal energy harvesting and CO2 sequestration. "We plan to further develop the modeling to incorporate realistic fault geometries of specific well-instrumented regions, like Southern California and Japan, to better understand their seismic hazard."

"Creeping fault segments can turn from stable to destructive due to dynamic weakening" appears in the January 9 issue of the journal Nature. Funding for this research was provided by the National Science Foundation; the Southern California Earthquake Center; the Gordon and Betty Moore Foundation; and the Ministry of Education, Culture, Sports, Science and Technology in Japan.

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Mory Gharib Named NAI Charter Fellow

Caltech's Mory Gharib has been named a charter fellow of the National Academy of Inventors (NAI).

According to the NAI, election to fellow status is a "high professional distinction accorded to academic inventors who have demonstrated a highly prolific spirit of innovation in creating or facilitating outstanding inventions that have made a tangible impact on quality of life, economic development, and the welfare of society."

Gharib (PhD '83) is the Hans W. Liepmann Professor of Aeronautics and professor of bioinspired engineering at Caltech. He is also the Institute's vice provost for research. Gharib's research group at Caltech studies examples from the natural world—fins, wings, blood vessels, embryonic structures, and entire organisms—to gain inspiration for inventions that have practical uses in power generation, drug delivery, dentistry, and more. Gharib is responsible for more than 59 U.S. patents.

Gharib will be formally inducted as a charter fellow during the second annual conference of the National Academy of Inventors in Tampa, Florida, in February.

Academic inventors and innovators elected to the rank of NAI Charter Fellow were nominated by their peers "for outstanding contributions to innovation in areas such as patents and licensing, innovative discovery and technology, significant impact on society, and support and enhancement of innovation."

"The natural world serves as the inspiration for many of my inventions," Gharib says. "But it is also inspiring to have been selected as a charter fellow of the NAI and to be included in a group with so many other leading innovators."

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Ares J. Rosakis to Receive P. S. Theocaris Award

The Society for Experimental Mechanics (SEM) will present the P. S. Theocaris Award for 2013 to Ares J. Rosakis, Caltech's Theodore von Kármán Professor of Aeronautics and professor of mechanical engineering, and chair of the Division of Engineering and Applied Science.

Given every two years, the award is named in honor of P. S. Theocaris, a legendary solid mechanics researcher, dynamic-fracture experimentalist, and past member of the prestigious Academy of Athens. The award recognizes recipients for distinguished, innovative, and outstanding work in optical methods and experimental mechanics. Rosakis will accept the award at SEM's annual conference in Lombard, Illinois, in June.

"Receiving this award is especially thrilling for me since I have had the honor of knowing Professor Pericles Theocaris since early childhood in Greece," says Rosakis. "As a high school student I was greatly inspired by his pioneering work on dynamic-fracture mechanics, high-speed photography, and the optical method of caustics, subjects which I still hold very dear to my heart. Indeed I consider his influence as playing a very important role during the first formative steps of my engineering and scientific identity."

Rosakis researches quasi-static and dynamic failure of metals, composites, and interfaces using high-speed visible and infrared diagnostics and laser interferometry. Recent research conducted by Rosakis combined engineering fracture mechanics and geophysics to gain a better understanding of the destructive potential of large earthquakes.

SEM specifically recognized Rosakis for his experimental discovery of "intersonic" or "supershear" ruptures or dynamic delamination cracks. These ruptures are capable of propagating at speeds that are faster than the shear wave speeds of the surrounding material, and can spread along fault planes in the earth's crust to produce supershear earthquakes. These ruptures also grow along weak interfaces in a variety of composite materials commonly used in engineering practice. SEM also is recognizing Rosakis for his seminal contributions in the area of dynamic failure and for developing methods to determine stresses in thin-film structures.

Rosakis received his BSc from the University of Oxford in 1978 and his PhD from Brown University in 1982, the same year he joined Caltech as an assistant professor. He was appointed associate professor in 1988 and professor in 1993 and was named von Kármán Professor in 2004. He also became the fifth director of the Graduate Aeronautical (Aerospace as of 2008) Laboratories at the California Institute of Technology (GALCIT) in 2004 and held that position through 2009, the year he was appointed division chair.

Rosakis holds 13 U.S. patents on thin-film stress measurement and in situ wafer-level metrology as well as on high-speed infrared thermography. He is the author of more than 260 papers on the dynamic deformation and catastrophic failure of metals, composites, interfaces, and on laboratory seismology. He is a member of the National Academy of Engineering and a fellow of the American Academy of Arts and Sciences. He recently received the commander grade of the French Republic's Order of Academic Palms.

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Hans Hornung Awarded Honorary Doctorate

Caltech professor emeritus Hans G. Hornung received an honorary doctorate from the Swiss Federal Institute of Technology (Eidgenössische Technische Hochschule, or ETH) Zurich, at a recent ceremony.

According to the award citation, Hornung was honored by ETH Zurich for his outstanding research contributions in the field of fluid dynamics and his "extraordinary ability to be inspiring when passing his knowledge on to his students."

Hornung, the C. L. "Kelly" Johnson Professor of Aeronautics, Emeritus, served as the fourth director of the Graduate Aeronautical (now Aerospace) Laboratories at Caltech.

"This is a very well-deserved international honor for Professor Hornung. As his colleague and a past director of the Graduate Aerospace Laboratories at Caltech, I have firsthand knowledge of his dedication to research and teaching," says Ares J. Rosakis, Theodore von Kármán Professor of Aeronautics and professor of mechanical engineering, and chair of the Division of Engineering and Applied Science.

ETH Zurich rector Lino Guzzella presented the honorary degree to Hornung in a ceremony on November 17 in the Hauptegebaeude, the main building on the Zurich campus. The other recipient of the honor was Lord Martin Rees, former master of Trinity College, University of Cambridge, and the United Kingdom's Astronomer Royal.

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Top 12 in 2012

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Credit: Benjamin Deverman/Caltech

Gene therapy for boosting nerve-cell repair

Caltech scientists have developed a gene therapy that helps the brain replace its nerve-cell-protecting myelin sheaths—and the cells that produce those sheaths—when they are destroyed by diseases like multiple sclerosis and by spinal-cord injuries. Myelin ensures that nerve cells can send signals quickly and efficiently.

Credit: L. Moser and P. M. Bellan, Caltech

Understanding solar flares

By studying jets of plasma in the lab, Caltech researchers discovered a surprising phenomenon that may be important for understanding how solar flares occur and for developing nuclear fusion as an energy source. Solar flares are bursts of energy from the sun that launch chunks of plasma that can damage orbiting satellites and cause the northern and southern lights on Earth.

Coincidence—or physics?

Caltech planetary scientists provided a new explanation for why the "man in the moon" faces Earth. Their research indicates that the "man"—an illusion caused by dark-colored volcanic plains—faces us because of the rate at which the moon's spin rate slowed before becoming locked in its current orientation, even though the odds favored the moon's other, more mountainous side.

Choking when the stakes are high

In studying brain activity and behavior, Caltech biologists and social scientists learned that the more someone is afraid of loss, the worse they will perform on a given task—and that, the more loss-averse they are, the more likely it is that their performance will peak at a level far below their actual capacity.

Credit: NASA/JPL-Caltech

Eyeing the X-ray universe

NASA's NuSTAR telescope, a Caltech-led and -designed mission to explore the high-energy X-ray universe and to uncover the secrets of black holes, of remnants of dead stars, of energetic cosmic explosions, and even of the sun, was launched on June 13. The instrument is the most powerful high-energy X-ray telescope ever developed and will produce images that are 10 times sharper than any that have been taken before at these energies.

Credit: CERN

Uncovering the Higgs Boson

This summer's likely discovery of the long-sought and highly elusive Higgs boson, the fundamental particle that is thought to endow elementary particles with mass, was made possible in part by contributions from a large contingent of Caltech researchers. They have worked on this problem with colleagues around the globe for decades, building experiments, designing detectors to measure particles ever more precisely, and inventing communication systems and data storage and transfer networks to share information among thousands of physicists worldwide.

Credit: Peter Day

Amplifying research

Researchers at Caltech and NASA's Jet Propulsion Laboratory developed a new kind of amplifier that can be used for everything from exploring the cosmos to examining the quantum world. This new device operates at a frequency range more than 10 times wider than that of other similar kinds of devices, can amplify strong signals without distortion, and introduces the lowest amount of unavoidable noise.

Swims like a jellyfish

Caltech bioengineers partnered with researchers at Harvard University to build a freely moving artificial jellyfish from scratch. The researchers fashioned the jellyfish from silicon and muscle cells into what they've dubbed Medusoid; in the lab, the scientists were able to replicate some of the jellyfish's key mechanical functions, such as swimming and creating feeding currents. The work will help improve researchers' understanding of tissues and how they work, and may inform future efforts in tissue engineering and the design of pumps for the human heart.

Credit: NASA/JPL-Caltech

Touchdown confirmed

After more than eight years of planning, about 354 million miles of space travel, and seven minutes of terror, NASA's Mars Science Laboratory successfully landed on the Red Planet on August 5. The roving analytical laboratory, named Curiosity, is now using its 10 scientific instruments and 17 cameras to search Mars for environments that either were once—or are now—habitable.

Credit: Caltech/Michael Hoffmann

Powering toilets for the developing world

Caltech engineers built a solar-powered toilet that can safely dispose of human waste for just five cents per use per day. The toilet design, which won the Bill and Melinda Gates Foundation's Reinventing the Toilet Challenge, uses the sun to power a reactor that breaks down water and human waste into fertilizer and hydrogen. The hydrogen can be stored as energy in hydrogen fuel cells.

Credit: Caltech / Scott Kelberg and Michael Roukes

Weighing molecules

A Caltech-led team of physicists created the first-ever mechanical device that can measure the mass of an individual molecule. The tool could eventually help doctors to diagnose diseases, and will enable scientists to study viruses, examine the molecular machinery of cells, and better measure nanoparticles and air pollution.

Splitting water

This year, two separate Caltech research groups made key advances in the quest to extract hydrogen from water for energy use. In June, a team of chemical engineers devised a nontoxic, noncorrosive way to split water molecules at relatively low temperatures; this method may prove useful in the application of waste heat to hydrogen production. Then, in September, a group of Caltech chemists identified the mechanism by which some water-splitting catalysts work; their findings should light the way toward the development of cheaper and better catalysts.

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In 2012, Caltech faculty and students pursued research into just about every aspect of our world and beyond—from understanding human behavior, to exploring other planets, to developing sustainable waste solutions for the developing world.

In other words, 2012 was another year of discovery at Caltech. Here are a dozen research stories, which were among the most widely read and shared articles from Caltech.edu.

Did we skip your favorite? Connect with Caltech on Facebook to share your pick.

A New Tool for Secret Agents—And the Rest of Us

Caltech engineers make tiny, low-cost, terahertz imager chip

PASADENA, Calif.—A secret agent is racing against time. He knows a bomb is nearby. He rounds a corner, spots a pile of suspicious boxes in the alleyway, and pulls out his cell phone. As he scans it over the packages, their contents appear onscreen. In the nick of time, his handy smartphone application reveals an explosive device, and the agent saves the day. 

Sound far-fetched? In fact it is a real possibility, thanks to tiny inexpensive silicon microchips developed by a pair of electrical engineers at the California Institute of Technology (Caltech). The chips generate and radiate high-frequency electromagnetic waves, called terahertz (THz) waves, that fall into a largely untapped region of the electromagnetic spectrum—between microwaves and far-infrared radiation—and that can penetrate a host of materials without the ionizing damage of X-rays. 

When incorporated into handheld devices, the new microchips could enable a broad range of applications in fields ranging from homeland security to wireless communications to health care, and even touchless gaming. In the future, the technology may lead to noninvasive cancer diagnosis, among other applications.

"Using the same low-cost, integrated-circuit technology that's used to make the microchips found in our cell phones and notepads today, we have made a silicon chip that can operate at nearly 300 times their speed," says Ali Hajimiri, the Thomas G. Myers Professor of Electrical Engineering at Caltech. "These chips will enable a new generation of extremely versatile sensors." 

Hajimiri and postdoctoral scholar Kaushik Sengupta (PhD '12) describe the work in the December issue of IEEE Journal of Solid-State Circuits

Researchers have long touted the potential of the terahertz frequency range, from 0.3 to 3 THz, for scanning and imaging. Such electromagnetic waves can easily penetrate packaging materials and render image details in high resolution, and can also detect the chemical fingerprints of pharmaceutical drugs, biological weapons, or illegal drugs or explosives. However, most existing terahertz systems involve bulky and expensive laser setups that sometimes require exceptionally low temperatures. The potential of terahertz imaging and scanning has gone untapped because of the lack of compact, low-cost technology that can operate in the frequency range.

To finally realize the promise of terahertz waves, Hajimiri and Sengupta used complementary metal-oxide semiconductor, or CMOS, technology, which is commonly used to make the microchips in everyday electronic devices, to design silicon chips with fully integrated functionalities and that operate at terahertz frequencies—but fit on a fingertip.

"This extraordinary level of creativity, which has enabled imaging in the terahertz frequency range, is very much in line with Caltech's long tradition of innovation in the area of CMOS technology," says Ares Rosakis, chair of Caltech's Division of Engineering and Applied Science. "Caltech engineers, like Ali Hajimiri, truly work in an interdisciplinary way to push the boundaries of what is possible."

The new chips boast signals more than a thousand times stronger than existing approaches, and emanate terahertz signals that can be dynamically programmed to point in a specified direction, making them the world's first integrated terahertz scanning arrays.

Using the scanner, the researchers can reveal a razor blade hidden within a piece of plastic, for example, or determine the fat content of chicken tissue. "We are not just talking about a potential. We have actually demonstrated that this works," says Hajimiri. "The first time we saw the actual images, it took our breath away." 

Hajimiri and Sengupta had to overcome multiple hurdles to translate CMOS technology into workable terahertz chips—including the fact that silicon chips are simply not designed to operate at terahertz frequencies. In fact, every transistor has a frequency, known as the cut-off frequency, above which it fails to amplify a signal—and no standard transistors can amplify signals in the terahertz range. 

To work around the cut-off-frequency problem, the researchers harnessed the collective strength of many transistors operating in unison. If multiple elements are operated at the right times at the right frequencies, their power can be combined, boosting the strength of the collective signal. 

"We came up with a way of operating transistors above their cut-off frequencies," explains Sengupta. "We are about 40 or 50 percent above the cut-off frequencies, and yet we are able to generate a lot of power and detect it because of our novel methodologies."

"Traditionally, people have tried to make these technologies work at very high frequencies, with large elements producing the power. Think of these as elephants," says Hajimiri. "Nowadays we can make a very large number of transistors that individually are not very powerful, but when combined and working in unison, can do a lot more. If these elements are synchronized—like an army of ants—they can do everything that the elephant does and then some."

The researchers also figured out how to radiate, or transmit, the terahertz signal once it has been produced. At such high frequencies, a wire cannot be used, and traditional antennas at the microchip scale are inefficient. What they came up with instead was a way to turn the whole silicon chip into an antenna. Again, they went with a distributed approach, incorporating many small metal segments onto the chip that can all be operated at a certain time and strength to radiate the signal en masse.

"We had to take a step back and ask, 'Can we do this in a different way?'" says Sengupta. "Our chips are an example of the kind of innovations that can be unearthed if we blur the partitions between traditional ways of thinking about integrated circuits, electromagnetics, antennae, and the applied sciences. It is a holistic solution."

 The paper is titled "A 0.28 THz Power-Generation and Beam-Steering Array in CMOS Based on Distributed Active Radiators." IBM helped with chip fabrication for this work.

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