Everyone is familiar with cardboard, the paper product commonly used to make boxes of all sorts. The problem with cardboard is that while it’s lightweight and has decent strength, the material isn’t suitable for many uses. For uses where more strength and durability are needed, a team of engineers from the University of Pennsylvania has created a new material called nanocardboard.
Nanocardboard isn’t meant to make fancy boxes of the future; this material is made from aluminum oxide film with a thickness measured in tens of nanometers. The material forms a hollow plate with a height of tens of microns and is a sandwich structure similar to corrugated cardboard, which is where the nanocardboard name comes from. The sandwich structure makes it ten thousand times as stiff as a solid plate of the same mass according to the engineers on the project.
The incredibly lightweight material would tip the scales at under a thousandth of a gram for a piece of material a square centimeter in size. Despite its lightweight and thin design, the material is resilient and can spring back into its original shape after being bent in half. The stiffness-to-weight ratio of the material makes it ideal for aerospace and microrobotic applications where every gram of weight is the enemy.
Besides being light and thin, the mechanical properties of nanocardboard make it an excellent thermal insulator. The engineers working on the project plan, in the future, to explore a phenomenon discovered in the nanocarbon material; when a light is shined on the nanocardboard, the material can levitate. The levitation happens when the surface temperatures on each side of the material are different, and a current of air molecules flows out through the bottom of the nanocardboard.
The image of the nanocardboard under a microscope above shows the unique basket weave pattern of the material. That pattern gives the material some of its strength and allows it to resist wrinkles, and is key to its resistance against bending. Nanocardboard can be bent and will recover as if the bending never happened.