Thin Strong Corrugated Aluminum Oxide

We are most familiar with aluminum oxide as corundum, a crystalline mineral. Corundum, combined with various impurities, form the gemstones ruby and sapphire. Many forms of aluminum oxide are considered to be ceramics, with typical characteristics of being hard, brittle and good insulators.

University of Pennsylvania researchers have discovered that by using atomic layer deposition to create corrugated pieces of thin film aluminum oxide that can be bent and twisted without damage. Light, strong, and flexible substances will find many uses in airborne applications and in space, such as solar sails.

Penn Researchers Make Thinnest Plates That Can Be Picked Up by Hand – [upenn.edu]

Researchers at the University of Pennsylvania have now created the thinnest plates that can be picked up and manipulated by hand.

Despite being thousands of times thinner than a sheet of paper and hundreds of times thinner than household cling wrap or aluminum foil, their corrugated plates of aluminum oxide spring back to their original shape after being bent and twisted.

Like cling wrap, comparably thin materials immediately curl up on themselves and get stuck in deformed shapes if they are not stretched on a frame or backed by another material.

Ultralight shape-recovering plate mechanical metamaterials – [nature.com]

Abstract
Unusual mechanical properties of mechanical metamaterials are determined by their carefully designed and tightly controlled geometry at the macro- or nanoscale. We introduce a class of nanoscale mechanical metamaterials created by forming continuous corrugated plates out of ultrathin films. Using a periodic three-dimensional architecture characteristic of mechanical metamaterials, we fabricate free-standing plates up to 2 cm in size out of aluminium oxide films as thin as 25 nm. The plates are formed by atomic layer deposition of ultrathin alumina films on a lithographically patterned silicon wafer, followed by complete removal of the silicon substrate. Unlike unpatterned ultrathin films, which tend to warp or even roll up because of residual stress gradients, our plate metamaterials can be engineered to be extremely flat. They weigh as little as 0.1 g cm−2 and have the ability to ‘pop-back’ to their original shape without damage even after undergoing multiple sharp bends of more than 90°.

SEE ALSO:
Things That Work Better in Space
Thin, Flexible, Wearable Electronics

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