The fact that scientists at MIT have been working on a new form of bulletproof visor doesn’t sound particularly newsworthy, but the additional fact that this breakthrough was inspired by a type of oyster certainly makes the story a little more unique.
MIT scientist Christine Ortiz and her team have studied the nanoscale structure of windowpane oyster shells, determining that the science behind their natural makeup may greatly improve the integrity of shields, visors and other clear, yet protective items commonly used by the military.
Oyster shells can endure repeated beatings without shattering, a trait that would be very desirable for combat armour. At present, shields and visors are fashioned from laminated glass. This material is tough and will often withstand a bullet, but it tends to fracture, reducing visibility and ensuring that it will not survive a second shot.
The windowpane oyster, however, has a see-through shell (used mainly for camouflage) that is made of 99% calcite mineral. Calcite crystals that occur elsewhere in nature shatter very easily, but they have been used for many different things throughout Human history.
Naturally occurring clear calcites (also known as ‘Iceland Spar’, ‘Optical Calcite’ or ‘Viking Sunstone’), which are formed by trapped air and water, were commonly used as rifle sights during the Second World War. In addition, the famous Norse explorer Leif Erickson – regarded by many historians as the first European to land in North America- is said to have used a piece in his navigations at sea (the double-refractory nature of the stone was said to help him locate the sun, even on a cloudy day).
In order to prevent the shells being brittle, the windowpane oyster has evolved an organisation of thin layers within its shell. These layers shift their orientation when exposed to pressure, which means that only shallow areas of the shell are affected by damage and fractures are prevented from spreading. In layman’s terms, windowpane oyster shells are shatterproof.
Ortiz and her team believe that applying this concept to clear armour and military equipment will yield a tougher (and more protective) type of material.
The windowpane oyster (known as Capis in the Philippines, where it has a province, Capiz, named after it) has quite a large habitat, stretching from the Gulf of Aden, to India, Malaysia, the Southern China Sea and the warm, coastal waters around the Philippines. In these areas, windowpane oyster shells can be easily collected on beaches, in lagoons and deeper out to sea (to a depth of about 100m).
The oysters are edible and they produce pearls, but the shells are more highly prized than the meat or even the pearls, being used to make decorative windchimes, lanterns, kitchen utensils and, surprisingly enough, actual windowpanes. Windows fashioned from oyster shells are fairly common in Asia, India and the Philippines.
The shells are also sometimes used in the creation of Parol, which is a type of star-shaped Christmas lantern commonly used in the Philippines.
If oysters prove to be the inspiration for the next generation of battle armour, then one would suppose that the old saying “make love, not war” is especially profound when applied to this story, given the oyster’s reputation as an aphrodisiac!