The research team created the folded surface in Howard Stone's laboratory in the mechanical and aerospace engineering department by carefully curing a layer of liquid photographic adhesive with ultraviolet light. By controlling how fast different sections of the adhesive cured, the team was able to introduce stresses in the material and generate ripples in the surface. The shallower ripples were classified as wrinkles and the deeper ones are called folds. The team found that a surface containing a combination of wrinkles and folds produced the best results.
Although the math underlying the process is complex, the actual production is straightforward. Loo said it would be quite practical for industrial purposes.
"Everything hinges on the fact that you can reproduce the wrinkles and folds," Loo said. "By controlling the stresses, we can introduce more or fewer wrinkles and folds."
Another benefit of the process is that it increases the durability of the solar panels by relieving mechanical stresses from bending. The researchers found the panels with folded surfaces were able to retain their effectiveness after bending. A standard plastic panel's energy production would be diminished by 70 percent after undergoing bending.
Loo said the researchers drew their inspiration from leaves. Seemingly a simple object, the leaf is a miracle of natural engineering. Its green surface is perfectly constructed to bend and control light to ensure that a maximum amount of solar energy is absorbed to create energy and nutrients for the tree. Recent work by Pilnam Kim, a postdoctoral researcher in Stone's lab, provided insight into how these microscopic structures could be applied to synthetic devices.
"If you look at leaves very closely, they are not smooth, they have these sorts of structures," said Loo, who is deputy director of Princeton's Andlinger Cent
|Contact: John Sullivan|
Princeton University, Engineering School