Fly eye inspires biomimetic surfaces for solar cell production

Penn State University researchers have discovered a way to pattern solar cells using the eyes of flies. This is an important step to moving biomimicry out of the lab and into the real world.

While Akhlesh Lakhtakia was growing up in India, he tried to kill flies with his hands.

He blamed his inability to catch the flies on the fact that he had small hands. But he knew that the flies could see him much better than he could see them.

Flies can see your hand coming. Their big eyes are positioned on their head, in a way that let's them see 270 degrees around them. Without a fly swatter, Lakhtakia didn't stand a chance.

"I thought about those things back then," he says.

He still does.

A few years ago, when Lakhtakia was in his lab at Penn State University, he was trying to figure out how to decorate a solar cell that captures light from the side to increase the efficiency of the cell. He thought, well flies do it.

"So we chose the eyes of flies," Lakhtakia says.

The engineering professor has created the first industrial way to pattern solar cells using the eyes of flies. "I'm not saying this will happen tomorrow, but it's in the realm of industrial possibility," he says.

Lakhtakia's grad student had the pleasure of getting the experiment started. The student left a piece of liver outside, and before long, flies swarmed around the meat. The flies were caught with a net and taken inside the lab. Killed with ethanol, the flies were ready for their heads to be chopped off and their eyes separated for good. The eyes were mounted on a glass slide.

Then, inside a vapor deposition chamber, evaporated nickel formed a thin film on top of the eyes. The resulting film was 250 nanometers thick (or thinner than your hair). To get the film to an ideal thickness of half a millimeter thick, the student dipped the slide into an electrolyte solution to allow the nickel ions to accumulate on top of the surface.

Then the student washed the solution off and threw away the glass slide.

"Remove the eyes and you are left with the impression of the eyes on the nickel surface. It's a cast. Then you put a polymer inside of it and the polymer will acquire the shape of the eyes. This way, you can make replicas of the eyes," he says.

Bioreplication is less than 10 years old — no one has figured out a way to automate the process. For now, it's done the hard by — by hand.

"You could make one copy of it from the original. Doing that on an industrial scale would deplete the natural source. Even if people don't like flies, it's still not a good idea [to use a fly for every copy]," Lakhtakia says.

We have to work on automating the process, he says. But this will take us a few years.

Lakhtakia is using similar techniques to create colored surfaces. That way, fabrics like bed sheets could have pretty colors because of their structure. Things can have colors in other ways than slopping paint on them. The method could also be used to solve crimes. Normally fingerprints on things like Wal-Mart bags are difficult to read, but Lakhtakia's patterning technique can read those hard-to-read surfaces.

But Lakhtakia's immediate attention is on scaling up his method of patterning solar cells with the eyes of a fly.

"Have you tried to swat a fly? I doubt it, unless you are quick like Bruce Lee," he jokes.

Well, clearly the professor hasn't seen this video of President Obama swatting a sucker during an interview:

Photo Credit: Akhlesh Lakhtakia, Penn State

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