The composition of seashells, bones, and teeth serves as evidence that nature already has the upper hand in creating a host of materials from individual atoms and molecules. While humankind has not yet achieved true molecular manufacturingmanipulating and assembling individual atoms on a large scalescientists are closing in on this goal around the world and here in Troy.
As head of the Rensselaer Nanotechnology Center, Siegel will oversee more than 30 researchers whose work spans nearly every discipline on campus from materials science, physics, chemistry, and biology to biomedical, chemical, and electrical engineering, and computer science.
In biotechnology research, for example, Rena Bizios, professor of biomedical engineering, and Siegel are investigating the potential of nanoceramics and nanoceramic/polymer composites as bone implants.
Nanophase materials have great potential which, to date, remains unexplored for many biomedical and tissue engineering applications, Bizios says. The Rensselaer Nanotechnology Center is providing the resources for pioneering research in the emerging field of nanophase biomaterials.
In this project, Bizios and Siegel have used nanoceramics of alumina and titania alone or in nanocomposites with such polymers as polyactic acid or polymethylmethacrylate. The goal is to formulate novel biomaterials with enhanced mechanical properties that are compatible with cells.
One finding their research has produced so far is that the nanoceramics and nanocomposites promote selectively enhanced functions of osteoblasts (bone-forming cells). This includes cell adhesion, proliferation, and deposition of calcium-containing minerals, an indication of new bone formation in the laboratory setting.
These are models for creating novel implant materials. Were not only looking at mechanical behavior, but how living cells interact with materials, Siegel says. Cells interact very differently with nanoscale materials. They react selectively and in the right way.
Smaller Is Better
The chemical composition of nanophase materials is the same as their conventional counterparts, but the particles or crystals that serve as basic building blocks of the material are much smaller. The smaller-size building blocks alter a materials mechanical, optical, electrical, and magnetic properties, and create, for example, copper five times harder than its conventional form and ceramics that bend instead of breaking.
Much of Schadlers research revolves around the custom design of polymer composites. Her work includes embedding nanomaterials into polymer and ceramic matrices.
Several features of nanoparticles can be exploited to control properties, Schadler explains. First, nanoparticles have a significantly larger surface area than microscale particles. Therefore, the volume of polymer affected by the nanoparticles is much larger than for micron-scale fillers. In addition, nanoparticles can be small enough that they dont scatter light. This creates an opportunity for improving the properties of transparent polymers without significantly decreasing their transparency.
Such research could result in better plastic windshields for military aircraft. In one project, Schadler is adding alumina nanoparticles to polymethylmethacrylate (PMMA), a polymer that is sometimes marketed as Plexiglas. We have been able to increase the ductility of PMMA by an order of magnitude, she says. In other composite systems, Schadler and her colleagues have increased the scratch resistance while maintaining optical clarity.
Carbon Nanotubes: Wire of the Future
One nanoparticle that has been the focus of much attention is the carbon nanotube. Pulickel Ajayan, associate professor of materials science and engineering, is at the forefront of research surrounding these quirky nanoscopic cylinders.
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