Bubble wrap - first invented as three-dimensional wallpaper - started protecting valuables in 1960 and is branded by the Sealed Air company. It's typically made from polyethylene, with a bubble-shaped side bonded to a flat side.
The new metallic form can offer protection in spaces only a few millimetres thick. Packaging can be made that is very thin and much stronger than the plastic variety.
Afsaneh Rabiei, professor of engineering North Carolina State University, and her team started with a thin sheet of aluminum and used a studded roller to form small indents in the sheet. Instead of capturing air in these indentations, she filled them with a foaming agent like calcium carbonate or titanium hydrate. When such agents are heated they form bubbles within the metal.
Then they bond this indented sheet to another flat sheet of aluminium, sandwiching the foaming agent in the separate recesses. Last, they heat the bonded sheets and the foaming agent forms bubbles, much in the way baking soda causes a cake to form its porous crumb. It is the bubbles that absorb the energy and shock from any load placed on the material.
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