By mimicking the outer coating of pearls (nacre or mother of pearl), researchers created a lightweight plastic that is 14 times stronger and eight times lighter (less dense) than steel. It could be applicable to vests, helmets, and other types of body armor as well as protective armor for ships, helicopters, and other vehicles.
The bulk of the material is a version of polyethylene (the most common plastic) called ultrahigh molecular weight polyethylene (UHMWPE), which is used to make products like artificial hips and guitar picks. When designing the UHMWPE, the researchers studied mother of pearl, which is created by mollusks by arranging a form of calcium carbonate into a structure that resembles interlocking bricks. Like mother of pearl, the material was designed to have an extremely tough outer shell with a more flexible inner backing that’s capable of deforming and absorbing projectiles.
The work is an advancement of soft armor in which soft yet tightly woven materials create a very strong net capable of stopping bullets — Kevlar is a well-known example. The UHMWPE-based material also has high thermal conductivity. This ability to rapidly dissipate heat further helps it absorb the energy of bullets and other projectiles. The team further experimented with UHMWPE-based material by adding silica nanoparticles, finding that tiny bits of the chemical could enhance the material’s properties and potentially create stronger armor.