Current plans and planning efforts associated with counterterrorism in the Federal sector are reviewed with emphasis on the positive role that materials research and engineering can play. Generic challenges associated with inspection and detection of materials and devices and broad opportunities for materials research and engineering contributions are discussed. The need for systems and system engineering approaches to the problem and the challenges that this poses to the materials community are highlighted and general approaches suggested.

The Kroto Research Institute, named after Sir Harry Kroto one of the University of Sheffield’s Nobel prize winners, is a multidisciplinary research centre that has Future Generation Materials as one of its strategic areas. The presentation will cover several of the research topics including work on nano-materials for enhanced vibration suppression, work on new imaging techniques with applications to security, developments in nano-characterisation of materials and research into new types of tissue for medical applications. Included in the presentation will be an overview of the projects that are being carried out in the new multidisciplinary research centre.

Composite materials have traditionally offered opportunities to tailor properties, reduce weight and maintenance in aerospace, marine, and civil applications. By thinking beyond these advantages and collectively considering material and system design relative to function, material designs can emerge that synergistically interact to create tailored multifunctional properties and performance that defy traditional trade-offs . Yet we just begun to take advantage of these opportunities. Recent developments in materials and computational modeling enable this new generation of composite materials systems. For example, nanocomposites have attracted considerable attention, because of their potential for multifunctional materials and properties that defy traditional tradeoffs, such as stiffness and strength, while adding capabilities beyond structural load carrying. Taking advantage of the unique ability to design and control interfaces and synthetic strategies and structures at the molecular scale, we can begin to create hierarchically structured composites with tailored multifunctional properties. Within this discussion we will highlight multifunctional engineering and scientific foundations for synergistic materials design as several scales. These include the vapor grown carbon fibers combined as an enhancement to low viscosity resins for composites that both toughen and introduce EMI shielding. We will explore efforts to combine both power generation and storage in structural systems through new processing methods. These endeavors are measured using a metric for multifunctional performance and discussed in the context of current abilities and future opportunities.

Nuclear radiation detectors are becoming increasingly important for the nuclear forensic analysis, homeland security against terrorist threats, long term monitoring of nuclear waste storage sites, and environmental safety. An ideal nuclear detector should combine a number of features presently distributed among many different types of detectors: high energy resolution, high sensitivity, room-temperature operation, scalability, robustness, etc. For example, high energy resolution of better than 0.2% at 1.33 MeV can be achieved using bulk Ge detectors. However, the need to cool down the detector to 110 K results in a “compact” system of a vacuum cleaner size. CdZnTe detectors offer good room-temperature performance with 1% energy resolution at 662 keV, but their linear size is limited to a few cm. The most commonly used NaI:Tl+ scintillating crystals can be grown in large size and operate at room temperature, but at the expense of poorer energy resolution of ~6-7% at 662 keV. The tradeoffs between different detectors become even more apparent when other parameters are considered, such as high speed, low cost, good proportionality, high stopping power, and so on. Nanotechnology offers new prospects for meeting those competing requirements.Nanosize devices have attracted tremendous interest over the last few years for a wide range of biomedical, biochemical sensing, and optoelectronic applications. So far, however, their potential has largely eluded the nuclear detection community. In this paper, we will review the current status of the emerging nanomaterials for nuclear detection applications, discussing the existing preliminary data, and the potential improvements in the detector cost, reliability, and performance the nanosize devices have to offer. For example, compared to currently used scintillating particles of the micrometer size, nanocrystals offer the prospect of significantly improved performance. Due to their small size, they are expected to have better solubility in organic polymer, inorganic sol-gel, or porous host materials and to cause much less scattering, which should result in higher efficiency. Due to much better overlap of the electron and hole wavefunctions, the optical transitions are expected to be much faster than in bulk materials, which should eliminate the major problem of relatively slow response of scintillator detectors.Over the last decade, the quest for an ideal scintillator has resulted in a large number of new materials with remarkable properties. Among those, lanthanide halides have produced the highest light outputs combined with speeds much faster than traditional materials. However, practically all of that effort had focused on investigating bulk single crystal materials. In contrast to wide exploitation of quantum confinement effects in optoelectronic and electronic devices, the physics and technology of inorganic scintillators is still limited to bulk materials.

The scalable fabrication of nanoscale features in 2-D arrays and isolable objects will play an important role in meeting numerous unmet needs in our Nation's security and defense portfolio. This lecture will survey the use of solvent resistant, chemically robust elastomeric molding materials for the fabrication of patterned arrays, films and particle technologies useful for energy storage, energy generation, power conversion, robotics and as probes and treatments of biological structures. Specifically we are exploiting the utility of curable perfluoropolyethers (PFPEs) as molds in soft lithographic imprint techniques. The PFPE materials show ideal properties for imprinting and molding to generate isolated objects that are uniform in size and dimensionality down to the sub 10-nm regime. A versatile “top-down” method, Particle Replication in Non-wetting Templates (PRINT), for the fabrication of particles having absolute control over size, shape and functionality will also be described. Fluoropolymer molding materials used in PRINT eliminate the formation of an interconnecting “flash layer” which plagues other soft lithographic techniques. Isolated, harvestable mono-disperse particles with a range of shapes can be fabricated down to the tens of nanometers size out of a wide range of materials, including the incorporation cargos useful for nanomedicine applications. The combination of the PRINT platform with well-developed printing and molding technologies, such as silk-screen printers and compression molding equipment, will allow for the creation of a “particle foundry” -- the functional equivalent of the continuous fabrication methodologies employed by the microelectronics industry -- for fabricating delicate organic particles necessary for use in emerging security and defense technologies.

As the size scale of device features becomes increasingly smaller, conventional lithographic processes are limited. Alternative routes need to be developed to circumvent this hard stop. Ideally, if existing technological processes are be used with novel materials, significant advances can be made. Block copolymers (BCP), two polymer chains covalently linked together at one end, provide one solution. BCP self-assemble into a range of highly-ordered morphologies, the exact nature of the morphology will depend upon the volume fraction of the components, where with size scale of the features is limited to the size of the polymers chains and are, therefore, nanoscopic in size. However, self-assembly alone is not sufficient. Rather, directed self-orienting self-assembly processes are required to produce devices with the required density and addressability of elements. This requires the design and synthesis of polymers that have well-defined characteristics such that the necessary fine control over the morphology, interfacial properties, and simplicity of processes can be realized. By combining tailored self-assembly processes, the bottom-up approach, with micro-fabrication processes, the top-down approach, faster, better and cheaper devices can be generated in very simple, yet robust, ways.

The use of MicroElectroMechanical Systems (MEMS) in weapons presents the opportunity to reduce the size and mass of components that perform safety and use-control functions. Microsystem technologies are disruptive, however, in the sense that they represent the use of non-traditional materials in these applications for which there may be insufficient data on performance, material interactions, and long term degradation phenomena. Fabrication methods for microsystems have a strong influence on surface roughness and chemistry. As the size of movable structures decreases, the forces due to physical phenomena such as capillarity, electrostatics, and Van der Waals interactions can become comparable to, or even exceed the forces due to mass or inertia, or the forces applied with microfabricated actuators. Surface interactions therefore become critical to the performance and reliability of microsystems. MEMS materials are frequently chosen based on the availability of a manufacturing infrastructure and process knowledge for patterning and etching the material, rather than the material properties themselves. The result is that surface treatments are required to achieve the desired performance and reliability. In this presentation, the common materials and fabrication technologies for microsystems will be reviewed, along with the major issues associated with those materials in defense applications. Surface treatments intended to address microsystem performance and reliability will be discussed, including the challenges associated with treatment of deeply-buried interfaces in complex structures. The response of these materials to long term aging in dormant storage, which can be a dominant factor for high-consequence applications, will also be examined.

Electrochemical biosensors for detecting specific sequences on DNA, for detecting specific proteins and for detecting specific small molecules will be described and recent progress will be summarized. The electrochemical biosensor for detection of specific sequences on DNA ((E-DNA sensor) utilizes electrochemically induced conformational changes to alter the redox current from a molecule attached to the end of a single strand of DNA comprising the complement to the target. The protein and small molecule sensors utilize aptamers (E-AB sensors) to provide the bio-specificity. Again, the binding of the target to the aptamer causes a change in the redox current from a molecule attached to the end of the aptamer.

Purpose: To develop practical sensors for detecting biothreat agents present both in air and in water. Biothreat agents investigated by the author’s lab include pathogens (Bacillus anthracis (BA) and E. coli O157:H7(EC)) and toxins (Staphylococcal enteroxin B). Method: Two recognition strategies have been successfully used: (1) the use of antibody specific to BA and EC, (2) the use of identifying DNA sequence specific to the pathogen. Results. PEMC are fabricated in the author’s lab by bonding a fused slica film to a piezoelectric layer and then anchoring the latter to a fixed end. Such mechanical structures exhibit high order resonance frequency near 1 MHz. Experimental measurements of mass change sensitivity are in the range of 1 ag/Hz to 1 fg/Hz depending on attached target antigen. We show that both Ab- and DNA-based strategies are successful. The limit of detection for both pathogens were less than 10 cells/mL in liquid. In the case of EC, tests included in food matrices and in the case of BA included in presence of other contaminating Bacillus sp. The Ab-based sensor showed fidelity in detection for 330 spores/mL in presence of 330,000 spores of Bacillus cereus and Bacillus thuringiensis. Of special note is exposure of the sensor to airborne Bacillus anthracis gave positive sensor response in 80% humid air. Detection of ~40 BA spores/L of air is achievable in near real-time with an estimated lower limit of detection of~5 spores/L of air in the configuration tested. Detection of EC in both food (ground beef) and buffer was achieved at 10 cells per mL. Large volume samples (1 liter) were easily processed with high sensitivity. SEB in both apple juice and milk was directly detectable at 2.5 femtogram per mL without a sample preparation step or the use of labeled reagents. DNA-based detection for EC was based on Stx2 gene, and successful detection using extracted genomic DNA is demonstrated using a few hundred cells in both beef wash and in buffer. Both SEM and low-pH buffer release confirmed antibody-based detection. Conclusions: We conclude that detection of BA spores and EC can be accomplished in a practical format in less than 10 minutes using Ab and in 30 minutes using extracted genomic DNA.

The use molecular circuitry to interconnect different molecules in series can be used to introduce chemically activated switches along the length of the molecular wire. It will be described how this approach greatly amplifies chemical signals and leads to the detection of ultra-trace chemicals with low-cost portable (hand-held) sensors. The signal amplification achieved by these methods is applicable to both optical (photonic) and electrical sensors. This presentation will focus on applications of this method to the detection of explosives, including the high explosives TNT, RDX, and PETN and explosive taggants. New methods based on carbon nanotubes will be demonstrated for the detection of chemical warfare agents as well as other chemicals that can be used to create improvised explosives.