Beauty, molecules deep

By John German

At the truly tiny scale of nanoparticles, attractions and repulsions among atoms and molecules often overwhelm the more ordinary forces at play in the larger-scale world. A pair of particles, for example, nudged close enough together, might snap like magnets into one.

Such nanoscale forces, driven in some cases by the momentary orientations of electrons, become a problem when the goal is to keep particles evenly dispersed in liquid – a challenge for manufacturers who want to make products featuring nanoparticle-enhanced films or coatings. Nanoparticles suspended in solvents at high densities tend to clump while the coating is drying, negating the benefits of their nanosized ingredients.

Improving the processing and manufacturability of such coatings and thin films is the primary goal of a research collaboration that began last spring among Sandia and a half dozen companies. The Nanoparticle Flow Consortium includes 3M, BASF, and Corning, among others. Sandia serves as the hub for the three-year, $2 million cooperative research and development agreement.

Nanoparticles make good building blocks for new and better materials because the materials can be, in essence, built from scratch at the molecular level. This allows chemists to take fuller advantage of principles of physics and chemistry to create materials with characteristics not available through traditional bulk chemistry methods.

Currently, however, most nanoscience takes place in research laboratories where very small amounts of matter are manipulated using specialized equipment. To manufacture consumer products, companies will need to master high-throughput, large-scale nanomaterial processing techniques.

The potential benefits are enormous. Embedding nanoparticles in coatings and films could result in materials with useful new properties: coatings that react to the environment, paint or glass that color-shifts like a chameleon, self-lubricating or self-healing surfaces, or antimicrobial coatings for hospital ventilation systems, for example.

The U.S. National Science Foundation estimates that by 2015, the worldwide nanotechnology market could reach a trillion dollars annually. Potential mass-produced, nano-coated consumer goods and materials on the horizon include improved flat-screen TV displays, stronger and more transparent glue, lightweight composites, specialized sealants for microelectronics devices, and new materials for sensing and medical devices.

“The amount of money involved is staggering,” says Randy Schunk of Sandia’s Multiphase and Nanoscale Transport Processes Department. The chemical, defense, aerospace, electronics, computing, health care, and other industries are expected to see nanotechnology advances worth tens to hundreds of billions of dollars each, he says.

Color-shifting paints are among the potential applications for nano-enhanced coatings.

The Nanoparticle Flow Consortium’s work will address two main technical challenges: stable dispersal of nanoparticles in solution during processing, and improved understanding of particles dispersed in materials under stress or flow and how these states are affected by nanoscale forces. Both were viewed by participants as limiting factors in manufacturing of nanoenhanced materials and thin films.

To address these issues, Sandia is developing modeling and simulation tools to understand liquid flow chemistry, nanoparticle dispersal stability, and particle control. Together with Sandia’s high-performance computers, the new software tools are expected to result in a predictive capability for nanoparticle processing – meaning materials and techniques with the highest chances of success can be designed on computers before they are ever tried in a laboratory. The modeling tools will be available to all consortium partners.

Corning’s proprietary fusion manufacturing process yields exceptionally clean, smooth, and flat surfaces, essential to the manufacture of LCD TV screens. (Image courtesy Corning Display Technologies)

Resolution of these technical barriers may open doors not only to advanced coatings, but to layered bulk materials as well, says Schunk.

“Manufacturable implies practical,” he says. “Companies need to disperse these particles in liquid, then cast them, coat them, layer them, or paint them on something, often over large areas. Such problems aren’t necessarily going to be addressed in a research lab.”

Nanoparticle dispersal in liquid is a key issue for the companies involved in the National Institute for Nano Engineering (NINE), a national hub for nanoscale engineering and education. NINE collaborators and students will benefit from the consortium’s work, he says.

The Nanoparticle Flow Consortium is modeled after a similar cooperative research effort that began at Sandia in 1996, the Coating Related Manufacturing Processing Consortium (CRMPC). The CRMPC included many of the same partners and resulted in a software package, GOMA 5.0, which far exceeded existing modeling capabilities for coating processes, Schunk says.