In desperate need of a more efficient structure for their tiny solar cells, engineers turned to the world's foremost expert on nanotechnology: Mother Nature. The corneas of flies are the perfect nanostructures for the next generation of solar cells.
This particular field of engineering is known as biomimetics, which is pretty much exactly what it sounds like: building structures that mimic their biological counterparts. A lot of biomimetic research focuses on insects, but it isn't always possible to transform an efficient biological structure into an easily replicable artificial structure.
As Penn State professor and lead researcher Akhlesh Lakhtakia explains:
"Bioreplication began about 2001 or 2002. All the techniques currently available are not conducive to mass replications. In many cases you can make as many replicas as you want, but you need an insect for each replication. This is not good for industrial purposes."
Oftentimes, the perfect biomimetic structure will have just the right mix of big and small features. The corneas of the blowfly species proved ideal:
"We needed an object large enough to manipulate that still had nanoscale features. These eyes are perfect for making solar cells because they would collect more sunlight from a larger area rather than just light that falls directly on a flat surface."
Blowfly eyes are hemispherical, compound structures, with each hemisphere covered with individual hexagonal eyes. As a whole, these eyes are macroscale structures, but their individuals feature tread into nanoscale territory. That's the perfect combination to both replicate the structure using a mold and then increase the size of the artificial duplicate without sacrificing any of the helpful individual details.
That last bit is absolutely crucial if these blowfly corneas are going to pave the way to a useful technology. An earlier paper by Lakhtakia and his colleagues came up with a design for new lenses using fly eyes that would improve solar cell function. They have been able to put together arrays of nine blowfly eyes to create replicable templates, although their next template will feature an array of 30 corneas. Once they have enough templates, they can tile them together and start creating much larger surfaces, which can then be used to build these fly-designed solar cells.