June 15, 2010
Next-Generation Advanced Materials: APL Science and Technology Anticipating Future Operational Needs
To ensure that APL’s sponsors have access to the technologies they need now and in the future, the Laboratory supports basic research in promising new areas that fill anticipated technology voids. Through close engagement with sponsors and a commitment to using internal research funding, APL conducts research that leads to breakthrough technologies for real-world challenges in national security, space exploration, and biomedicine.
Over the last few years, APL researchers have successfully applied advances in materials science and nanostructures to create engineered materials of great potential value to Department of Defense and NASA applications. As these technologies have matured, the research effort has been redirected to include materials that are biologically inspired, suited for biomedicine applications, or made using living organisms as well as smart materials that change properties dynamically. New materials with exciting properties that have been developed as a result of these efforts are described below.
Physiologically Responsive Polymers
APL is working on a polymer that releases medication only when triggered by physiological changes in a patient’s body, reducing the likelihood of overmedication for disorders that flare up temporarily. The material combines synthetic and biological polymers in a cross-linked hydrogel. When a specific biomarker, such as a protein or hormone, comes into contact with the polymer, the hydrogel’s bonds are broken and the polymer dissolves and releases its medication. This self-regulated drug-delivery system could elegantly perform the work of both a sensor and automated dispenser and could remove the need for an expensive implant device and perhaps even the need for continuous medical supervision. It could be ideal for conditions such as allergic reactions or dropping blood pressure.
APL is developing lightweight nanocomposites that could be used in improved body armor, optically clear structural materials such as safe windows, and biomedical applications such as contact lenses or corneal repair. The materials might even be produced in the field because the main ingredients are sugar, light, water—and bacteria. Certain organisms, such as the bacterium Acetobacter xylinum, synthesize nanosized ribbons of pure cellulose as part of their normal metabolic processes. These fibers exhibit better mechanical stiffness and lower density than conventional fiberglass. APL’s scientists and engineers are exploring ways to maximize the strength, stiffness, and scalability of lightweight composites made from the cellulose.
APL has found a solution to locomotion and power-generation challenges that have hampered production of robots smaller than a centimeter. Such mini-robots offer unprecedented capabilities to sense, manipulate, and explore difficult-to-access environments, and they could one day move themselves with the help of artificial cilia. Cilia mimic the tail-like projections that help cells move or sense their environment, and they are among the smallest mechanical actuators found in living systems, measuring 1–10 micrometers in length and 40 nanometers in diameter. They bend to generate locomotion or fluid flow and sense local forces and acceleration when bent by them. The microscopic mechanical actuators that APL has built are based on flexible magnetic filaments made from ferromagnetic cobalt nanoparticles. The project’s ultimate goal is to build chip-based devices for both microfluidic flow detection and pumping. Specific applications include a micropump, a micro-flow sensor, an acoustic sensor with built-in match filter, an energy harvester, and an acoustic imaging array.
Piezo Polymeric Materials
The Laboratory is investigating various applications for a new piezoelectric material whose piezoactivity and mechanical properties can be altered individually to suit different applications. The material, originally developed at The Johns Hopkins University, can be produced in the form of thin films or fibers (sub-micrometer to millimeter) directly from a polymer solution, allowing customization of the material’s shape or incorporation into a polymer coating. Its mechanical stiffness can be controlled for particular applications or tuned to match that of the surroundings (such as air or water) for increased transduction sensitivity. The material’s performance is comparable to that of polyvinylidene fluoride, with high sensitivity and low power requirements. This new piezomaterial is ideal for sensor-based applications, including hydrophones, microphone vector arrays, piezoelectric coating applications, and energy harvesting.
An APL-developed primer additive could reduce the amount of time and money the Marine Corps and the Navy spend replacing and rehabilitating equipment because of corrosion. At a cost of more than $2 billion per year, corrosion is among the Corps’ biggest expenses. Designed to mimic the self-healing ability of skin, the primer additive, called Polyfibroblast, consists of microscopic, hollow nickel/zinc spheres filled with a resin of moisture-curable polyurethane-urea. When scratched, the resin ejects from the broken microcapsules to completely fill the crack, creating a polymer scar that protects the underlying metal surface from further exposure to water. In addition, the nickel/zinc shells provide galvanic protection in those cases where healing is incomplete. Polyfibroblast is designed to work as an additive with existing military-grade primers. Testing is under way to determine the extent to which its capabilities improve corrosion resistance. This research is funded by the Office of Naval Research.