Implications of Emerging Micro- and Nanotechnologies (2002) / Chapter Skim
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3. Major Areas of Opportunity
3. Major Areas of Opportunity
Pages 40-142
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From page 40... ...
Sensors, discussed in the next section, provide the raw data. Electronic signal processing is applied to the sensor outputs to interface with the larger-scale information processing and communication systems.
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This section starts with computing devices. Transistors, switches, and integrated circuits are covered; a separate section on space electronics is included because of the unique environmental requirements of space and its importance to the Air Force.
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The continuing hegemony of CMOS devices and circuits is based on substantial improvements and the introduction of highly innovative ideas. At the 2001 International Electron Devices Meeting, Intel announced a transistor operating at 3.3 terahertz.4 At this same meeting, Advanced Micro Devices (AMD)
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Tour-de-force feats with carbon nanotubes (see next section) and molecular-layer transistors have succeeded in actually fabricating transistors and even simple logic circuits.
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Spin-Based Electronics Following the development of the very successful giant magnetoresistive read heads for magnetic storage and magnetic field sensors, a new area of spinbased electronics is emerging.23 The concept is to use the spin of the electron in suitably designed devices to perform logic operations. One can imagine that information now stored as the presence or absence of charge could alternatively
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From page 45... ...
All of these issues are likely to be considerably more complex as dimensions are further reduced. This suggests that the first uses of molecular electronics are likely to be as adjuncts to, rather than replacements for, the integrated circuit.
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.28 Ink jet printers have been used to achieve transistor gate lengths of 5 micrometers and also to fabricate arrays of organic light-emitting diodes.29 Ink jet techniques have been also extended to such unconventional areas as deposition of suspended alloys and metallic or magnetic nanoparticles offering advantages for electronic applications.30 Organic transistors are envisioned for use as switching devices for active matrix flat panel displays (liquid crystal, organic light-emitting diodes, and "electronic paper"~.3i In addition, organic and semiconductor white-light-emitting structures are anticipated to come into use in the future and to have a significant impact on energy use. All-polymer integrated circuits for use as radio frequency identification tags and for various sensors have been proposed.
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From page 47... ...
Because of their unique self-assembled and atomically perfect structures, carbon nanotubes exhibit unusual electrical, mechanical, and chemical properties. These special properties, such as the ability to carry exceptionally high current densities in long molecularly perfect "wires" and unusually high mechanical strength at the limit of small 'fiber' diameters, have generated much interest in the potential applications of nanotubes.
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From page 48... ...
Mechanical Properties As a result of their seamless cylindrical structure, carbon nanotubes have low density, high stiffness, and high axial strength. Theoretical studies and recent experimental measurements suggest that the Young's modulus and breaking strength of single-wall carbon nanotubes are exceptionally high.3 Carbon fibers with a tensile strength up to 6 GPa are commercially available, while initial experimental measurements on 4-mm-long single-wall carbon nanotube (SWNT)
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2000. Tensile loading of ropes of single wall carbon nanotubes and their mechanical properties.
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As they meet at the other side of the ring, if the distance traversed is less than the coherence length, interference effects appear as a function of magnetic field. This magnetoresistive behavior is fairly straightforward for regular geometric features.
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From page 51... ...
This enables new vacuum electron devices such as flat cathode ray tubes, smaller and more robust x-ray tubes for inspection and sterilization, and vacuum microelectronic integrated circuits for extreme temperature and radiation environments. Vacuum microelectronic flat panel displays utilize tens to thousands of active emitters per pixel, FIGURE 3-1 Power versus frequency for high-frequency microwave devices.
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, and in this regime Earth's atmosphere is still present, but at exceedingly low densities. Earth's atmosphere and magnetic field together protect terrestrial dwellers from the cosmic rays, high-energy protons, and high-energy electrons normally present in the space environment.
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technology is now being considered for commercial electronics because it can provide enhanced low-voltage operation, simplified circuit fabrication, and reduced circuit sizes relative to bulk silicon counterparts.42 TFSOI would be particularly TABLE 3-1 Approximate Radiation Hardness Levels for Semiconductor Devices Technology Total Dose (reds) (silicon)
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This graph was generated using data supplied by the on-line Space Environment Information System (SPENVIS) .43 Figure 3-2 indicates that commercial CMOS devices should have at least several millimeters of shielding to survive a year in LEO orbit.
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Specialized radiation-hard devices are available, but they are expensive and are about two to three technology generations behind their commercial counterparts.44 Fortunately, commercial CMOS foundry processes, in general, have increasing total dose hardness as device feature sizes decrease. The increased hardness apparently results from decreased gate oxide thickness.45 One commercially available 0.25-micrometer process has an apparent total dose limit of greater than 100 kilorads without design changes and greater than 500 kilorads with the addition of guard bands, etc.46 Latchup and SEUs must still be dealt with, however.
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From page 56... ...
Vacuum integrated circuits are one possibility for radiation hardness over an extremely wide operating temperature range; this would be ideal for ultrasmall or essentially twodimensional spacecraft with minimal mass for radiation shielding or thermal inertia. Total dose hardness of commercial CMOS may continue to increase with time, but latchup and SEU prevention will necessitate the use of specialized gate designs and additional on-chip protection circuitry.
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represent one such implementation of this basic idea. They consist of arrays of quantum dots in which the state of an array exists in various electronic configurations.
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Additional algorithms must be discovered and a useful quantum computation must be demonstrated before thought can be given to practical applications. The basic quantum computer consists of a loosely coupled array of binary quantum states, each of which represents a single qubit.
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There is great interest in developing quantum computation. Numerous approaches are currently being investigated: various schemes employing trapped ions, cavity quantum electrodynamics, nuclear magnetic resonance, neutral ions in an optical lattice, superconducting circuits, electrons floating on liquid helium, photon exchange interactions, and spintronics and quantum dots in solid-state systems.
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Until now, constrained by the limits of microtechnology, attempts to mimic human brain functions have dealt with the brain's extreme complexity by using mathematical simplifications (i.e., neural networks) or by carefully analyzing intelligent behavior (i.e., artificial intelligence)
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Magnetic Storage Magnetic storage includes magnetic disks, tapes, and a new class of magnetic memory, random access nonvolatile memory (MRAM) , with disks providing vast high-speed data storage, tapes providing archival storage of huge data sets, and MRAM providing a radiation-hardened, nonvolatile substitute for conventional electronic random access memory.
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Indeed, spin transport phenomena that occur on the nanoscale are responsible for the commercial success of giant magnetoresistive (GMR) magnetic read heads and magnetic field sensors.
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The ease of manufacture and the competitive nature of such a device compared with magnetic memory crossbar structures and with conventional magnetic disks have yet to be determined. Yet another process using molecular memory is holographic information storage, where data are stored in a volume that retains optical phase information
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Discussion of these systems aspects is deferred to the next section, "Signal and Information Processing and Data Fusion." Here, the hardware aspects of communications are discussed. Secure Communications An emerging benefit of some of the physics of nanotechnology is communications security and secrecy.
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New materials for both optical and RF applications are emerging from continuing investigations of semiconductors. Two examples are self-assembled quantum dots for laser systems and gallium nitride (GaN)
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Quantum dots will be discussed in more detail below; for the nonce it is sufficient to appreciate that nanoscale confinement in three dimensions serves to further modify the electronic wavefunctions and density of states, now to an atomic-like discreteness, and to increase the local electronic density of states. As is clear from this brief overview, micro- and nanotechnologies are already having dramatic effects on optoelectronics.
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From page 67... ...
For the most part, the fabrication of these materials is based on self-assembly, specifically the Stransky Krastanov growth7i mode, where the interplay between lattice mismatch stress and surface tension of the growing film leads to the formation of isolated islands or quantum dots. Figure 3-5 shows an atomic-force microscope image of an array of InAs quantum dashes on InP with a photoluminescence peak at 1.6 mm, matching the long-haul telecommunications band.72 As in all electronic devices, the material demands are very exacting.
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From page 68... ...
Looking backwards, improvements in control of semiconductor materials always have led to improvements in electronic and optical devices and to new and improved systems applications of those improvements. There is every reason to expect that today's developments will lead to tomorrow's devices with vastly improved characteristics that will enable new applications for both military and commercial markets.
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From page 69... ...
Optical fibers are a ubiquitous example of twodimensional waveguides that have had a major impact on communications and sensing technologies. One-dimensional Bragg gratings (layered structures where the reflection is built up by the in-phase addition of many small amplitude reflections)
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From page 70... ...
Many MEMS sensors have been commercialized, notably pressure sensors, microphones, accelerometers, and angular rate sensors. The third class of MEMS includes mostly actuators, essentially the inverse of sensors, because they transduce information into some physical, chemical, or biological effect.
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Proceedings of the IEEE/LEOS Summer Topical Meetings on Optical MEMS and Their Applications. New York, N.Y.: Institute of Electrical and Electronics Engineers, Inc.
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In 2000, four start-up companies making optical MEMS mirrors were sold for a total of almost $6 billion in stock; in the spring of 2002, their value was much less. The decline in the stock market and in the pace of telecommunications infrastructure development has delayed the introduction of MEMS switches into the long-haul communications grid, but they are now beginning to be used.
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Optical MEMS, especially those for the transmission of information and display of images, have come on the scene as the Internet has become an indispensable part of modern life for individuals, schools, businesses, organizations, and governments. In a similar fashion, RF MEMS are emerging from laboratories into commercial use right in the middle of the wireless revolution.
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Optical MEMS will find greatest use for the fiber-optic communication of information and for the display of images.89 RF MEMS will be widely used in cell phones and other wireless communications equipment.90 Signal and Information Processing and Data Fusion Without intelligent processing of data, the Air Force will not be able to take advantage of the advances in sensing and communications. Indeed, there is danger of being buried in data, of all of the communications pipes being fully engaged in transmitting reams of bits mostly of low value and of a severely restricted ability to respond.
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The communications links will have to be exceptionally robust. Large amounts of data will have to be transmitted securely and reliably over a complex ~1 ~ Command Center Data Fusion Target Prioritization Communications 1 Remote Sensor Suite Parallel Interconnect Local Processing & Data Compression Complex Sensor Array (\ Weapon System Target Acquisition Guidance Smart Munition A/, /~/ FIGURE 3-8 Schematic of a situational awareness system.
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Data Fusion Data fusion is largely a software development, although it also requires display devices that maximize the transmission of key concepts and ideas to a decision maker. The ability to gather data from multiple sensors and to manipulate the data to get the best information will increase along with the capabilities of computers.
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, March. Available online at |
From page 78... ...
Software, application-specific integrated circuits (ASICs) , embedded computers integrating software and hardware for specialized applications, and radiation-hardening and packaging for hostile environments must be designed by, and for, the military, to take advantage of these advances.
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materials, have clear radiation hardness benefits; others, such as molecular electronics, have yet to be evaluated in this context but are likely to exacerbate the problems. Finding 3-2.
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The Air Force strategic nanotechnology R&D plan, as presented to the committee, is focused on hardware concepts without appropriate consideration of total systems solutions. It is well known that over the past 15 years the commercial sector has made increasing investments in architecture and software concepts to design advanced systems.
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One important direction for distributed sensor research is "smart dust,"93 where large numbers of millimeter-scale, MEMS-based sensors communicating by wireless RF or optical links are dispersed over an area of interest. Clearly, networks such as these call for research into the size, functionality, and power consumption of individual nodes and into the communications and network architectures and hierarchy necessary to optimize their usefulness, especially in uncooperative environments.
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From page 82... ...
Impact of MEMS Within the scope of semiconductor-based devices, but outside the range of nanotechnologies and squarely in the range of microtechnologies, are MEMSbased sensors, including MEMS inertial sensors, magnetometers, room-temperature IR focal-plane arrays, acoustic and seismic sensors, and chemical and biological threat sensors. Of these, the MEMS pressure sensors and inertial sensors (accelerometers, angular rate sensors, and combinations of these)
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From page 83... ...
A large fraction of these payload sensors are imaging systems, where electric components will benefit in reduced weight and volume and increased functionalityfrom developments in micro- and nanotechnologies as discussed in the previous section. Electromagnetic Spectrum Sensors The Air Force's role in space requires space-based smart sensors for battlespace surveillance,95 including imagery and various modes of sensing.
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Space-based surveillance specifically requires improvements in power consumption, cost, and size in far-infrared sensors.~°i The ongoing revolution in nanomaterials may also provide better infrared-transmitting materials for windows and seeker domes. Reduced cooling needs for IR detector arrays are being explored in several ways, including biomimetic sensors,~02 quantum dots and carbon nanotubes,~03 and micromachined bolometersi04 and halometer arrays.
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From page 85... ...
. Larger format, higher resolution IR imaging arrays based on the use of silicon substrates with II-VI IR sensor arrays, including the direct growth of high-quality HgCdTe on silicon, as well as HgCdTe on CdZnTe, are under development.~05 Integration with silicon technology also provides the potential for lower costs at higher volumes by adopting some of the silicon microelectronics industry's fabrication tools and approaches.
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From page 86... ...
These diodes were fabricated using an InAs/AlSb/GaAlSb hetero structure in a lattice matched configuration grown by MBE and had an area of 4 square micrometers. These devices can be used as backward and zero-bias diodes with both high sensitivity and low direct current power requirements.
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From page 87... ...
Many sensor types are used to determine this orientation, including optical sensors for the Sun and stars and magnetic field sensors for determining their orientation with respect to Earth. More recently, monitoring the phase shift in the signal from different GPS satellites has become useful.
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Micromachined angle rate sensors monitor Coriolis forces, which are proportional to the angular rotation rate. Inertial sensors consist primarily of accelerometers and gyroscopes.
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Honeywell has a three-axis magnetic sensor hybrid based on magnetoresistive transducers,~7 Nonvolatile Electronics, Inc., manufactures application-specific magnetic sensors based on the giant magnetoresistive (GMR) effect, and another magnetometer concept is being developed at Johns Hopkins Universityii9 using the Lorentz force to measure vector magnetic fields.
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From page 90... ...
When bonds between an adsorbed species and a surface rupture, the amplitude changes, enabling sensitive detection of selective components adhering to a surface.~23 Changes in electrical conduction represent another approach to nanosensors. One such recent effort reveals changes in the conductivity of carbon nanotubes (CNTs)
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This scheme has been reported to give sub-picomolar sensitivities. Magnetic fields from submicron beads are used to detect forces between nanoparticles with the Bead Array Counter (BARC)
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. However, owing to system weight penalties and the difficulties of installation and repair, they have been used infrequently in aircraft and space applications.
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While the MEMS pressure belt described above is intended for measuring the pressure distribution on a wing in flight, nanoscience has provided an alternative solution for wind tunnel measurements. When fluorescent dye molecules are applied as paint they act as tiny oxygen probes, reacting by altering the fluorescent intensity in response to the local oxygen concentration.
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MEMS sensors for these parameters already exist and can be mass-produced for inexpensive environmental monitoring packs. Knowing what, when, where, and how a limit was exceeded is critical during the spacecraft flight readiness review.
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MEMS sensors coupled to data transceivers can be used in a wireless network system onboard the vehicle and on the launch site. The telemetry data can channel real-time or near-real-time information to a ground-based data storage system for postlaunch review.
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Data fusion is the field that addresses appropriately combining massive quantities of data. Micro- and nanotechnologies will play a role in data fusion by providing faster and smaller high-performance computing and information processing.
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Numerous small but cheap and sufficiently capable terrestrial robots could be of use to the Army and the Marine Corps, especially in urban warfare. All Services might benefit from the availability and behavior of large numbers of small air vehicles that are enabled by microtechnologies.
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The resurgence of the commercial MEMS sensor industry represents an opportunity for the U.S. Air Force to harvest improvements in military-specific MEMS devices.
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From page 99... ...
Large, distributed fixed arrays and moving swarms of multispectral, multifunctional sensors will be made possible by emerging microand nanotechnology, and these will lead to significantfundamental changes in sensing architectures. Concepts such as smart dust and distributed communication networks actively exploit the technological capabilities of emerging micro- and nanotechnologies.
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From page 100... ...
Biomimetics for Improved Sensing, Communications, and Signal Processing New sensing, communications, and electronic signal processing ideas might be drawn from an understanding of the "intelligent" behavior of neurons and cells. Cells are known to sense and respond to thermal, optical, chemical, mechanical, and electrical stimuli, e.g., elongation due to shear stress,~48 i49 i50 and galvanotaxis,~5i i52 but the underlying mechanisms are not well understood.
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From page 101... ...
The very large difference in open versus closed ion-channel conduction provides built-in amplification for this sensing mechanism, promising single-molecule detection sensitivity. Integration of this technology with integrated circuits is an obvious next step to provide the necessary high-density signal acquisition and processing.
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From page 102... ...
In recent years, biomedical engineering has made numerous, significant advances in this arena, including the artificial heart, artificial joints and limbs, and muscle-stimulating electrodes. Micro- and nanotechnologies make these devices less invasive by reducing size and increasing "smarts" through the integration of high-speed signal processing and control circuitry and through advances in biocompatible materials.
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From page 103... ...
STRUCTURAL MATERIALS Introduction The range of operational requirements for the most visible parts of military systems the physical structures and platforms is exceptionally broad and often extreme. Structures of special military importance include satellites and other spacecraft along with their specialized structural components, aircraft, land vehicles, water vehicles, missile systems and other weaponry, and warfighter support and protective equipment.
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From page 104... ...
A structural materials topic that is especially relevant to this study but generally overlooked when considering nanoscience's importance to macromilitary systems is structural materials for microelectromechanical devices. Since the miniaturization of electronic and sensor systems by way of MEMS technologies is essential for future defense systems, it is important to consider the technical issues and opportunities associated with the nanoscale materials needed to construct MEMS components.
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From page 105... ...
Nanoscale control of the grain structure of lightweight aluminum and aluminum alloys could be of value especially for aerospace structures. In addition, improvements in mechanical properties and the allowed operating temperature of titanium and titanium alloys are being pursued using nanoscience approaches.
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From page 106... ...
Also discussed at the workshop were severe plastic deformation processes that "work" materials to produce ultrafine grain sizes and increased strength. The equal-channel angular pressing type of severe plastic deformation is reported to be especially promising for Air Force applications such as lightweight aerospace structures.~67 The mechanical strength of nanosize, superstrong fibers such as carbon nanotubes and perhaps other materials such as boron nitride nanofibers, coupled with the lower density of these materials, offers the potential for much lighter composite structures that are stronger and tougher than conventional structural materials.
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From page 107... ...
Also at an early stage are methods for fully characterizing the basic properties, especially the mechanical properties, of assemblies of structures,~70 and for using them in practical structures. The superior aerodynamic performance enabled by use of lightweight structural materials of suitable yield strengths would be of particular value to the Air Force.
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From page 108... ...
For example, the extremely high thermal conductivity of carbon nanotubes is cited as a property that could be incorporated into thermal management components on surfaces or embedded in system structures, along with the favorable mechanical properties for lightweight structures.~74 More generally, it is envisioned that nanocomposites specifically tailored for their thermal
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From page 109... ...
One such concept is the use of self-assembled monolayers and multilayers of organic materials that exhibit inherent self-healing from scratches and similar damage as protective coatings, corrosion inhibitors, or adhesion promoters.~76 The AFRL is investigating the self-passivating and self-healing properties of polymeric nanocomposites used in connection with the well-known practice of using organic or inorganic fillers to reinforce polymers. Examples of nanoelements used for this purpose are layered silicates and carbon nanotubes.
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From page 110... ...
The grain size and deposition and annealing history are among the important factors in determining residual strain and the effect that this will have on the overall MEMS process. To date, MEMS mechanical properties have been studied most thoroughly in polysiliconi77 and in the sacrificial layers most often used in the MEMS process flows, such as silicon dioxide and silicon oxynitride films.~78 Also being investigated are the effects of metal fatigue and anelastic creep on metal MEMS mechanical structures produced by various processes and involving such materials as Au, Ni, and Ni alloys.
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From page 111... ...
The primary areas of technical development supporting improved structural materials include these: modeling and simulation deposition, fabrication, consolidation or assembly processes for forming the materials characterization, testing, and analysis at the nanoscale scale-up and manufacturing issues Some very specific technical issues relating to nanocrystalline materials include the following: .
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From page 112... ...
The quality control and process monitoring tools that will be needed for full-scale manufacturing using nanomaterials are still further away from realization at this time. The myriad of structural materials issues involved in the design, process flow, and assembly of MEMS devices are the key obstacles to deployment of high-performance MEMS components in military systems.
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From page 113... ...
Nanoscience as applied to the structural materials used for MEMS components is key to the successful deployment of MEMS technology. Unresolved issues such as stiction prevention, sidewall morphology, and durability and stability of micromechanical structures are obstacles to the deployment of reliable MEMS sensors and actuators in military systems.
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From page 114... ...
Subscale experiments have demonstrated that such active control can be used to alter the turbulent nature of the flow, perhaps leading to laminar flow vehicles with dramatically increased range and payload compared with existing aircraft. A second flow control application uses unsteady manipulation of the boundary layers to generate large forces and moments to achieve control and maneuverability of the flight vehicle.
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From page 115... ...
These issues must be addressed by full-scale flight-testing programs. Vehicle Health Monitoring As mentioned in a previous section on sensors, distributed MEMS-based sensors can be used to measure pressure, velocity, and shear stress distributions on aerodynamic surfaces to aid in flight vehicle development and qualification.
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From page 116... ...
Evolutionary Improvements One class of evolutionary improvements to gas turbines is MEMS-based flow control concepts, which are in many ways similar to those discussed for air vehicle aerodynamics. Improvements to the steady-state aerodynamics through flow control of gas turbine propulsion systems could include inlet and compressor end wall aerodynamics.
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From page 117... ...
. Technical issues for these evolutionary improvements to air-breathing turbomachinery include the integration of MEMS sensors and actuators onto curved surfaces, the transmission of data across rotating surfaces, the development of instability control algorithms and active control for specific applications, and the ability of MEMS sensors and actuators to survive high-temperature chemically reacting flows without fouling.
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From page 118... ...
One of the first might be the micro air vehicles (MAVs) under development by DARPA for surveillance and reconnaissance applications.
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1997. Micro-heat engines, gas turbines, and rocket engines The MIT microengine project, AIAA Paper 1997-1773.
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could obviate the need for aircraft hydraulics, a subsystem that is very complex and maintenance-intensive, becoming a nontraditional enabling technology for an all-electric aircraft. Large air vehicles use shaft power takeoff from the propulsion system to generate electric power for onboard needs.
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From page 121... ...
Since solid rockets burn for a limited time once ignited, a layer of internal insulation is used to shield the casing from high-temperature exhaust; this allows composites with polymer binders to be used. An obvious application of microand nanoengineering to solid rockets might be the use of carbon nanotube composites if significantly improved strength-to-weight ratios are achievable; this could significantly decrease casing mass.
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From page 122... ...
Technical issues include determination of nanopowder oxidation rates in contact with the fuel/oxidizer to establish propellant storage lifetimes, control of engine instabilities with faster-burning propellants, and the possible use of coatings on the nanopowders to chemically stabilize them. Liquid Propellant Rocket Motors Liquid propellant rocket engines offer higher exhaust velocities than solid rockets in return for increased complexity and cost.
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From page 123... ...
Spacecraft Propulsion Chemical Propulsion MEMS-scale liquid propellant rocket engines offer significant evolutionary advantages over conventional engines and also enable new space systems concepts. MEMS-based thrusters with ultrasmall micro- to millinewton thrust levels are needed for emerging micro-, nano-, and picosatellites.
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From page 124... ...
Six micromachined glass layers form a liquid storage tank, gas/liquid separator, gas plenum, gas distribution plumbing, and nozzles for a cold gas propulsion system. While this set of glass wafers was fabricated using direct-write laser-patterning of Foturan™ glass, mass production would utilize Foturan™, planar masks, and UV exposure much like the photopatterning step in the fabrication of semiconductor wafers.
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From page 125... ...
Similar digital thruster efforts have been funded by AFOSR and the French national space agency.~87 i88 Electric Propulsion Electric thrusters use electric power to accelerate propellant molecules, atoms, or ions. The advantage of this approach is that the specific impulse can be more than an order of magnitude greater (600 to 5,000 seconds)
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From page 126... ...
Field emission sources are currently under development as an enabling technology for flat panel displays, simplified microwave tubes, and vacuum microelectronics.~90 i9i i92 Examples of field emission sources include Spindt cathodes, diamond like carbon coatings, and carbon nanotubes.~93 i94 i95 Field emission
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From page 127... ...
Electrodynamic tethers exploit Earth's magnetic field and the local space plasma environment in LEO to generate either power or thrust; they can operate either as motors or electric generators. In the power generation mode, the v x B Lorentz force drives a current in an Earth-pointing conducting tether when the tether velocity has a component perpendicular to the local magnetic field.
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From page 128... ...
The LEO-to-GTO tether boost facility mentioned above would require a 100-kmlong tether of several millimeters diameter and a mass of 8,300 kilograms. The tether material was Spectra 2000™, a highly oriented polyethelyne with a tensile strength of 4 gigapascals and a density of 0.97 grams per cubic centimeter.202 A carbon nanotube-based composite could cut this mass by more than an order of magnitude, resulting in lower system launch masses or increased tether lengths for higher energy transfers.
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From page 129... ...
Nanoengineered materials may provide better conversion efficiencies by allowing the use of multiple quantum well absorbers. Solar Dynamic Electric Power Generation MEMS opens up other possibilities that might be attractive for some applications.
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From page 130... ...
Graphite is currently used as the lithium-storage anode; it has a storage capacity of one lithium ion for six carbon atoms. Recent research by Otto Zhou and colleagues at the University of North Carolina has shown that carbon nanotubes apparently have twice the lithium storage capacity per carbon atom.
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From page 131... ...
Emerging microtechnology has achieved preliminary success in sensing and controlling the boundary layer on full-size, subsonic airfoils. New devices for controlling gas and liquid flow, fabricated using m~crotechnology, promise to increase the power and reliability of a~r-breathing, full-size propulsion units.
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2000. High-performance all-polymer integrated circuits.
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2001. Logic circuits with carbon nanotube transistors.
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Applied Physics Letters 77(8)
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From page 135... ...
2000. Technical Insights, R-263: Optical MEMS: Worldwide Markets For a Strategic and Convergent Technology.
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Briefing by Forrest (Jack) Agee, Air Force Office of Scientific Research, to the Committee on Implications of Emerging Micro and Nano Technologies, National Academy of Sciences, Washington, D.C., August 16.
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Briefing by Gail J Brown, Air Force Research Laboratory, Materials and Manufacturing Directorate, to the Committee on Implications of Emerging Micro and Nano Technologies, Holiday Inn, Fairborn, Ohio, October 2.
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Briefing by Forrest (Jack) Agee, Air Force Office of Scientific Research, to the Committee on Implications of Emerging Micro and Nano Technologies, Holiday Inn, Fairborn, Ohio, October 2.
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2000. DC electric fields induce rapid directional migration in cultured human corneal epithelial cells.
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2000. Tensile loading of ropes of single wall carbon nanotubes and their mechanical properties.
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2001. In situ transmission electron microscopy study of the strength and stability of nanoscaled structural materials.
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2001. Carbon nanotube cathode with low operating voltage.
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