Thinner than paper, but super tough
Nanotechnology research aims to unlock the secrets of matter on the atomic scale, where materials can behave much differently than they do in everyday life, becoming stronger despite weighing next to nothing.
The trick is enabling these small wonders to interact with macro-scale objects while maintaining those special traits.
Researchers at the School of Engineering and Applied Science have taken a step forward in this quest, making nanoscale plates that are a thousand times thinner than a sheet of paper but strong enough to be picked up and manipulated by hand.
The work, led by professors Igor Bargatin and Prashant Purohit along with postdoc Keivan Davami, could lead to advances in aviation and other areas where lightweight, high-strength materials are needed.
Anyone who has wasted a sheet of cling wrap knows that thin, flexible films can be tricky to handle. The traits that make cling wrap clingy—low weight and pliability—also make it prone to curling up and sticking to itself.
Scaled down to the atomic level, this problem becomes even more pronounced. Nanoscale films must be stretched like a canvas on a frame, or put on a rigid backing, to prevent this curling.
“The problem is that frames are heavy, making it impossible to use the intrinsically low weight of these ultra-thin films,” Bargatin says. “Our idea was to use corrugation instead of a frame. That means the structures we make are no longer completely planar; instead, they have a three-dimensional shape that looks like a honeycomb, but they are flat and contiguous and completely freestanding.”
Aluminum oxide is deposited in precisely controlled atomic layers, resulting in plates that are between 25 and 100 nanometers thick and have the plates’ characteristic hexagonal divots.
“It’s like an egg carton, but on the nanoscale,” says Purohit.
In addition to providing rigidity, the corrugation also makes the plates less susceptible to tears. Cracks will usually stop at one of the internal walls, rather than propagating through the entire plate.
Aluminum oxide is a ceramic, but the plates can be bent, twisted and squeezed like flexible plastic, springing back into shape once released.
“The first time we saw it, I could hardly believe it,” says Bargatin.