‘A solution looking for a problem,’ but fascinating nevertheless

It is not unusual for a technology that was invented for one purpose to ultimately find other applications; indeed, the adjunct usage often has wider and/or more significant impact. The example that immediately springs to my mind is Gore-Tex, the material that makes outerwear and footwear waterproof.

Gore-Tex is a porous material constructed from polytetrafluoroethylene (PTFE), the same material that coats non-stick frying pans. The pores are of such size that they allow water vapor molecules to pass through, but block water molecules, which are larger in size. However, the membrane was not invented with parkas or boots in mind. Rather, the company — W.L. Gore Associates — first marketed the material for use in the manufacture of artificial veins and arteries, because it mimicked the osmosis properties of the real thing. It was only later that the company experimented with applying the membrane to fabric.

At the time, garment manufacturers were in a quandary. Waterproof rubberized fabrics were available, but they quickly caused the wearer to overheat, because they weren't breathable; on the other hand, no breathable fabric at the time was waterproof. The introduction of Gore-Tex solved this conundrum, and the invention proved so noteworthy that Robert W. Gore was inducted into the U.S. National Inventors Hall of Fame in 2006.

The reason I bring this up is that a couple of months ago I sat in on a presentation at the Radio Club of America's technical symposium given by Dr. Nathan Cohen, the CEO of Fractal Antenna Systems. Cohen — who holds a Ph.D. in astrophysics, 28 U.S. patents, and pioneered the invention of fractal antennas, filters and metamaterials — started by speaking about the advantages of fractal technology.

"Fractals can be used to get multiple frequencies that are next to each other … so you can use the fractal design, to get wideband coverage," Cohen said.

Cohen went on to talk about how fractal loops — "RF Legos" — can be combined to create all sorts of interesting things, for example, invisibility cloaks.

"An invisibility cloak is a device that passively allows you to see the back of an object without seeing the object itself," he explained.

Essentially, invisibility cloaks cause radio signals to de-couple as they reach an object, travel around the object, and then reunite in phase on the other side. To demonstrate, Cohen had one of his associates, named Peter, stand in a cylinder that had "about 10,000 little fractals on it." When he turned on his network analyzer, it indicated that the presence of his associate — i.e., the obstacle — had created attenuation of 20 dB. With the fractal-driven invisibility cloak in place, the attenuation dropped to 0 dB over 50% bandwidth.

"So, we cloaked Peter," Cohen said.

Fractal technology might provide a means for resolving co-site problems, Cohen said.

"Let's make the towers disappear; let's make the cables disappear; let's make the support structure disappear; let's make other antennas disappear at the frequencies you want things to work at," he said. "You essentially can make all of these things transparent at the other frequencies."

From a military perspective, in addition to stealth applications, cloaking technology could be incorporated into wearable vests that would protect personnel from electromagnetic pulses, Cohen said.

"It basically would be a deflection shield," he said. "The wearer wouldn't feel [the pulse] — the energy is going to go around and out the other side. So, maybe in the future, unfortunately, we might have to worry about Star Wars-type things like people getting hit with lasers."

In terms of other applications, Cohen joked that invisibility cloaking largely is a "solution looking for a problem." Perhaps so, but it is fascinating nonetheless.

Update on 1/15/13.

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