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Nano Lab's Tools Address Government Needs April 2008
Before the Nanotechnology-Biotechnology Laboratory opened in 2006, MITRE's scientists and engineers had to be content with just doing simulation, modeling, and other theoretical investigations of nanotechnology. Since then, with state-of-the-art laboratory tools, they have been expanding their groundbreaking research to include physical experimentation. "For 15 years, MITRE has been instrumental in developing systems engineering programs with the government to exploit developments in nanoelectronics," says Carl Picconatto, the Nano Lab's director and lead scientist. "Expanding our efforts beyond modeling and simulation to include physical experimentation was a very natural step, and an important one to position MITRE to better serve our government clients. Over the past two years, we have greatly increased our prototyping and testing capabilities to better assist the government in developing nanosystems." Today the Nano Lab's projects range from nano-enabled energy systems to the development of "nano-noses" for nose-like sensing. Meanwhile, a companion Biotechnology Lab supports projects in computational biology, analysis of proteins and nucleotides, and rapid diagnosis of biological agents. The co-location of these two labs on MITRE's McLean, Va., campus fosters stronger collaborations between the two disciplines, allowing them to share their equipment and ideas with one another. The Nanotechnology-Biotechnology Laboratory is the brainchild of James Ellenbogen, senior principal scientist of MITRE's Nanosystems Group. He first proposed such a laboratory in 1997, then in 2003 teamed with Picconatto and MITRE biotechnologists Jordan Feidler and John DiLeo in planning the present combined lab. Though the Nanosystems Group has been performing broad-based research and development in nanotechnology since 1992, Ellenbogen emphasizes that the laboratory has taken this work into a new dimension. "The Nano Lab is helping MITRE build physical prototypes of integrated nanosystems and test them, as well as just design them," says Ellenbogen. "We're helping the government maintain U.S. technical preeminence in nanotechnology by harnessing innovations in basic science and technology in order to engineer them into very dense—and sometimes very tiny—extended systems integrated on the nanometer scale." Latest Research Tools The Nano Lab's equipment would light up the eyes of any nanotechnology researcher who likes to push atoms and molecules around. First of all, there's a scanning probe microscope that uses atomic force microscope (AFM) methods for surface characterization of properties like topography, elasticity, friction, adhesion, and electrical/magnetic fields. It also uses a scanning tunneling mode to acquire data for images at the atomic scale (see sidebar). For fabricating components, there is a high-precision wire bonder and an electrostatic discharge-safe packaging and component assembly unit. A state-of-the-art electronic probe station and a suite of electronics equipment permit detailed measurement and characterization.
Picconatto points out that the facility also has a fully functioning chemistry lab, including a gas chromatograph/mass spectrometer. Chromatography separates compounds by chemical activity, while mass spectrometry determines each compound's identity. "It can do anything a state-of-the-art chemistry facility can do, and we're using it in conjunction with our electronics efforts for the government," he says. Sniffing Out the Bad Guys Most of the work in the Nano Lab is centered on four experimental focus areas that are of particular interest to MITRE's government clients. In one of these areas, the lab is conducting prototyping and testing on nano-enabled sensor systems. This also involves research on odorants, especially their role in biometric identification. Nanosystems group leader Brigitte Rolfe leads this effort, working toward the integration of nanosensors into nose-like electronic systems. Electronic sensors that detect odors aren't new. They're used in the perfume industry for quality control, in industrial settings to monitor the emission of noxious gases, and even in common appliances to detect leaks or other malfunctions. The artificial noses that currently exist in the commercial world are about the size of a credit card and contain approximately 20 individual sensors. However, to come close to working as well as natural noses, you need millions and millions of sensors working together as a system. That means shrinking the individual sensors down to the nanoscale. Fortunately, development of nanoscale electronic sensors has blossomed in recent years. "MITRE is using a systems engineering approach to integrate these discoveries into extended systems for more truly nose-like sensing," says Rolfe. Carbon Nanotube Separation Another focus area in the Nano Lab is the development of nanomaterials, and, in particular, the development of carbon nanotube (CNT) separation techniques. CNTs have unprecedented physical and electrical properties, but unfortunately they can be produced only in mixtures of different types that exhibit a wide range of electrical behaviors, from metal to semiconductor. That's a big problem for electronics applications, since metal nanotubes produce short circuits.
About eight years ago, MITRE researchers decided to try to separate CNTs rather than focus on how to make a single type. "We hold two patents on potential separation processes and continue to refine them," says Picconatto. The patents are based on the CNTs' intrinsic property of chirality (pronounced ky-rality), or handedness. An object is chiral if it is not interchangeable with its mirror image—similar to how your right and left hands are reflections of one another, but are not the same. Chirality in CNTs is exhibited by a twist in their structure along their length. This twist can be expressed as an angle or by two index numbers. Small differences in chirality can produce radically different behaviors. For example, a (12, 0) tube is a metal but a (12, 1) tube is a semiconductor. "Finding a way to mass produce CNTs of a single chirality has been called the 'holy grail' of nanotech," Picconatto says. "Industry has worked for over 10 years trying to make batches of nanotubes of only a single type at a time, but hasn't been successful." Calculations done by MITRE and its collaborators suggest that CNTs with different chiral angles should orient differently on certain surfaces. Further, the energy differences of these orientations are much greater than expected and could form the basis of a separation technique. "When the nanotubes deposit on a graphite substrate, they want to orient themselves at specific angles to the atomic lattice of the graphite," he says. "The angle depends on the chirality. We're trying to develop this effect into a viable bulk separation process." Nano-Enabled Power Systems The Nano Lab's third focus area is nano-enabled power systems. "We're doing independent verification and validation on new nano-enabled energy storage devices and power-delivery devices," Picconatto says. "The government needs to confirm the performance of these devices for use in traditional acquisition programs like communications systems or smart munitions." To meet such needs, the Nano Lab has built testbeds for nano-enabled batteries and nano-enabled supercapacitors. "We're also developing prototype hybrid power delivery systems that combine the high-energy density of batteries with the high-power density of supercapacitors," he continues. "Such a system would use a nano-enabled, high-energy battery to meet its average energy needs, but switch to a high-power supercapacitor for an instantaneous boost when a large power drain is required. While there are some R&D challenges with each type of subsystem, this is largely a systems integration problem where we are trying to build an effective hybrid system that combines high-energy batteries with supercapacitors to get power profiles that fit specific applications." Nanoelectronics R&D The Nano Lab's fourth focus area involves the development of nanoelectronic systems for specialized applications. This path expands upon MITRE's original nanotechnology focus of designing ultra-dense electronic systems. Also, it embraces a project that began several years ago to develop a six-legged millimeter-scale robot in order to study the integration of micromachines and nanoelectronics. Fabrication and prototyping of that system continues, but now this focus area also develops special-purpose nanoelectronics for next-generation military systems. Along with those efforts, the lab has a suite of equipment for testing and measurement of these prototype nanosystems. MITRE's government clients clearly appreciate the Nano Lab's work. When the lab opened, it had no direct support, only internal funding. Now customer support is three times the amount the company invests. As the lab's reputation grows along with its work program, Picconatto is committed to making sure the lab's capabilities meet the government's needs. One client even purchased an additional piece of equipment for the lab's semiconductor parameter analyzer so that MITRE could perform the specific measurement the client wanted. "It was the first time we had a major piece of R&D equipment purchased directly for our laboratory," says Picconatto. "MITRE's targeted development in state-of-the-art infrastructure allowed the government to make a relatively small investment to customize our lab for its needs. Our original lab equipment acquisitions were designed with this in mind, and we've included this concept as an element of our multi-year plan for future lab development."
—by David A. Van Cleave Related Information Articles and News
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