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Nanotech Briefs: Why is the Army interested in nanotechnology, and what areas are of greatest interest?

Dr. Steven McKnight: We, like the rest of the scientific community, are extremely excited by the promise of nanotechnology and specifically, we believe that it is the control of matter at the nanometer-length scale that will provide revolutionary capabilities in some of the products being used or anticipated for use by soldiers. We view it as a breakthrough in technology and science that will provide capabilities to soldiers that presently don't exist, or provide substantial improvements to those that they are using now.

We have three major thrust areas: nanomaterials by design; nanoelectronics, nanophotonics, and nanosensors; and nanobiotechnology. My area of expertise is in nanomaterials by design. There are three thrust areas in nanomaterials: the synthesis and characterization of new nanomaterial building blocks, which includes new organic or polymeric-based nanomaterials; new inorganic-based nanomaterials (ceramics and nano-metals); and the generation, characterization, and assembly of nanomaterial building blocks. We also are looking for structural applications, as well as what we call functional or multifunctional applications for these building blocks.

NB: What are some of the specific nanotechnology applications being researched at the ARL?

McKnight: One of things that we are very excited about is the ability to trigger mechanisms that haven't been used before to be able to get some sort of behavior. In terms of getting new mechanisms to absorb energy or to transfer a load in a structural application, we feel the ability to control matter at that level will allow us to design materials that will capture and trigger some of these mechanisms.

We are using nanosilica in a couple of different ways, including shear-thickening fluid composites (STF). We take a submicron colloidal dispersion of silica particles and a carrier fluid such as polyethylene glycol, and if you engineer it right, the properties of this fluid are very unique in that they flow at low loading rates (slow rates) and behave like fluids. When they are subjected to higher shear rates or higher loading rates, they change their properties dramatically, so they almost become like a solid. What we’ve tried to do is take that mechanism and apply it to something that would be unique in terms of its performance. So we've taken those fluids and have actually impregnated fabrics, whether they are Kevlar or nylon fabrics, and have made composites.

Traditional composites, such as fiberglass, are generally made with fibers and some sort of polymeric resin such as epoxy or polyester, or some other polymer. After you have processed it, it is a solid (similar to the materials in golf shafts, tennis rackets, or on an airplane). What's unique about these STF composites is that they are deformable at normal rates. So, it's like a heavy fabric that can deform, is conformable, and is reconformable, but once you have deformed it at very high rates, it hardens and you can see some very interesting applications. For example, we've demonstrated that these materials have very good stab resistance. You can make fabrics that are nearly impenetrable to an ice pick. We are currently researching how they perform in ballistics applications. This is an example of a mechanism available to nanoscale materials, which we've applied to make a new capability that does not currently exist — a flexible material that has some sort of stab resistance.

Other nanomaterials applications include nanocrystals and ceramics, and how they might be used in armor applications. The current interceptor body armor being used by our soldiers in Iraq consists of a ceramic insert on top of ballistic fabrics, and the ceramic plays a very important role. We believe that by controlling the crystalline structure at the nanometer scale in such ceramics, we can dramatically improve the strength and penetration resistance of the ceramics so that in the next generation of ceramic-based armors, we would get higher levels of performance at reduced weight. This would occur by controlling the defects and the microstructures at the nanoscale.

NB: How will nanotechnology support tomorrow's warfighter?

McKnight: I see nanotechnology supporting the warfighter in two primary areas, the first being lighter-weight materials that will lead to lighter-weight equipment. The advances being made in developing lightweight materials derived from nanotechnology will work its way into reducing the weight of the equipment that our soldiers have to carry. So, we can certainly enable greater mobility on the battlefield.

The second area is increasing capabilities. I think the pervasiveness of nanotechnology is going to be such that our soldiers will have much more awareness on the battlefield and they will have better awareness of fellow soldiers. The pervasiveness of nano sensors will allow for increased battlefield awareness.

We'll also develop things that have multifunctional capabilities that currently do not exist. We'll have uniforms that not only clothe and feed the soldiers, but also have embedded sensors that will protect the soldiers from ballistics and chemical and biological threats.

The Army has started to evaluate water-repellant treatments based on nanotechnology. I think that within 2-3 years, we will have much better water repellency, which would lead to greater comfort for the soldier. Some applications have longer timelines because there is quite a bit of effort associated with getting things integrated into an affordable system for hundreds of thousands of units. One of the things limiting our ability to insert technologies that will benefit the soldier is solving integration issues in an affordable way.

NB: Are their possible commercial applications for any of this ARL nanotech research?

McKnight: We had a very successful spinoff of our first nanotechnology company two years ago. Dr. Ray Yin, who works in our labs, had developed nanotechnology-based methods to improve the performance of biosensors. He was working on military-relevant applications, but he has since spun off his company to make improved biosensors for the military. He saw a number of applications in which his technology would have a direct impact on commercial applications.

What he has done is use a concept called nanomanipulation and dendridic polymers to improve the performance of traditional immunoassays used in the biotechnology industry to detect whether there are specific biological entities present in a test. This is one example of where there are clear commercial applications.

We've been approached about making fabrics for garments worn by correctional officers in prisons who often have to go into rather nasty situations to quell disturbances. A lot of the weapons fabricated by inmates are knives or shank-type geometries. So, we may be able to provide technologies that could protect against that sort of threat.

There are a number of applications that could have a direct impact on civilian sectors. One that hasn't come out of ARL, but out of the Army, is better food packaging. There's some work going on at the Natick Soldier Center in which they are using polymer nanocomposites to make better food packaging materials. Of course, this is important to the Army because we ship all of our foods to wherever we are.

We simply want nanotechnology to be part of what we do: it is another scientific tool that our folks can use to help solve problems for soldiers.

Find out more about nanotechnology's importance in aerospace and defense applications in the feature on page 12 of the January issue of Nanotech Briefs. Learn more about the Army Research Lab at: www.arl.army.mil