Twenty-seven year-old materials engineer Andrea Hill and her colleagues, Jennifer Lalli and Rick Claus, are “growing” their novel, electrically conductive textiles in a make-shift washing machine, incorporating their trademarked material Metal Rubber™ as an integral component.
“We can spin gold and silver into flexible fabrics and they are electrically conductive and nearly transparent,” Claus, Virginia’s Outstanding Scientist for 2001 and a professor of engineering at Virginia Tech, says.
The new nanotextiles could be used for a number of applications including as a shield for potentially harmful and disruptive radio frequency (RF) radiation.
“A cell phone can be wrapped in it and the incoming and outgoing signals are killed. It blocks the RF,” Claus, also the president of NanoSonic, explains. “It might be possible to make a thicker but lightweight conductive fabric for electric power workers that would not limit their performance, but that would reduce the effects of electric power line radiation.”
Although there is no federally mandated RF exposure standard, research is continually questioning potential hazards associated with RF electromagnetic fields, associated with consumer goods such as cell phones and the effects of living near an electric power line.
Some of the other advantages of NanoSonic’s novel e-textiles over its competitors are its greatly reduced weight, low manufacturing costs (with only aqueous byproducts), the ability to stretch the material without the incorporated metal and polymer nanoparticles separating, and durability to withstand repeated washings, according to its inventors.
The interdisciplinary team of chemists and engineers are able to generate their e-textiles onto pre-patterned templates, using their patented, environmentally friendly, room temperature nanotechnology manufacturing process. The different patterns allow the designers to fashion their e-textiles with specific mechanical and electrical properties in order to meet different material needs.
To date, they have produced several types of flexible fabrics, foams and fibers that incorporate the properties of Metal Rubber™. And they have met another challenge of the technology of working with nano-materials; they have up-scaled production to macro-sized materials, as large as a 4’x8’ sheet of plywood one might buy at a local hardware store.
Metal Rubber™, introduced two years ago and touted in the August 2004 issue of Popular Science as “holding promise for morphing wings and wearable computers,” is a unique substance. It has the elasticity of rubber and the electrical conductivity of steel. NanoSonic manufactures Metal Rubber™ using its patented self-assembly process, assembling it molecule by molecule, the hallmark of nanotechnology.
Hill led the development of the e-textiles, and collaborated with Lalli, vice-president of business development and the primary scientist who created Metal Rubber™, and Claus.
In e-textile manufacturing, weight is of significant concern, especially when designing clothes for military, firefighters or police. Military in the field might already be carrying some 130 extra pounds of weapons, rations, waters, gas masks, and protective clothing. Firefighters’ flameproof suits weigh an average of 30 pounds. Any additional hazardous chemical or biological protective wear used in any of these occupations is yet another heavy layer.
“NanoSonic’s new e-textiles weigh less than 0.0070 grams of metal per cubic centimeter,” Claus explains “while other e-fabrics actually weave in a true metal component, typically just metal wires” adding significantly to the overall weight and greatly reducing its mechanical and environmental robustness.
“The extreme low-weight of NanoSonic’s conductive fabric, ideal for integrating sensors into the material, has attracted interest,” Hill says.
These low-weight fabrics would allow the military to sew full e-textiles with the capabilities of antennas in the backpacks of its personnel, and when they are on the battlefield, individuals could be monitored as to their body temperature, blood pressure, and heart rate. Additionally, critical, lifesaving decisions could be made by those monitoring the feedback during a crisis or battlefield situation, Claus explains.
Other e-textiles do not have the ability to stretch and return to their original shape “without the metal layer flaking off,” Hill says. With Metal Rubber™ grown into the material, NanoSonic’s e-textiles can be stretched without damage because there is no coating material to flake off.
In the manufacturing process, Hill says her fabrication technique “took one-third of the time of typical electrostatic self assembly (ESA) processing methods” used in nanotechnology. “Based on the faster ESA fabrication, we were able to develop a method to scale-up the textile size for larger conductive fabrics,” thus producing the plywood-sized sheet of fabric.
The low-cost, environmentally friendly e-textile manufacturing process is due to Hill’s cleverness. With assistance from NanoSonic’s laboratory technician Michele Homer, an artist by background, they built their make-shift simulated washing machine. They installed simple elongated flow-controlled tube reactors that allowed the introduction of positively and negatively charged nanoparticle solutions to introduce the electrical conductivity during the conventional agitation process.
NanoSonic was founded in 1998 in cooperation with Virginia Tech, the state’s leading research university. Claus holds the Lewis A. Hester Chair of Engineering at Virginia Tech. Hill is a 2003 Virginia Tech materials science and engineering graduate, and the College of Engineering’s Outstanding Young Alumnus for 2005-06. Lalli received her doctorate in polymer chemistry from Virginia Tech in 2002.