Since Apple announced the iPhone 7 to a resounding meh in San Francisco on September 7, the air has been filled with laments for the dearly departed headphone jack. Underneath these woeful cries can be heard whispers of a new rumor: next year, Apple may make an iPhone with a case made out of ceramic rather than metal.
Two things suggest the possibility. First, the company has started selling a watch with a shiny white ceramic case: the Apple Watch Edition, which costs $1,249. Second, the company has a handful of patents describing the design and manufacture of a “handheld computing device” with a ceramic case. Given ceramic’s potential to shatter, its limited color options, and the expense it adds to manufacturing, though, making such a phone would be risky.
The Apple watch case is a blend of zirconia and alumina ceramics. These and other high-tech ceramic materials are very resilient. Ceramic engine parts and dental fillings, for example, are resistant to wear and tear. In a portable electronic device, this should translate into scratch resistance—the beautiful polished sheen of the ceramic watch case is likely to endure.
Another good quality of ceramics is that they are rigid. A ceramic watch or phone case could be made very thin without being vulnerable to warping. Apple has a history with these sorts of problems. In the 2014 Bendgate crisis, some customers who bought the iPhone 6 Plus claimed that the phone’s thin aluminum case bent after being carried in their front pocket (video).
Still, if you’ve ever dropped a ceramic plate or mug and seen it shatter, the notion of a ceramic phone may be a head-scratcher. Even high-tech ceramics are brittle, prone to catastrophic failure and shattering—albeit at much greater forces than a mug. However, zirconia-based ceramics like Apple’s are particularly prized for their toughness, says Katherine Faber, a materials scientist at Caltech in Pasadena, California. When a crack forms in the material, stress induces the crystal structure to change to one that is more stable. “This pushes on the crack and makes it more difficult for it to propagate,” she says.
Even so, it’s very easy to imagine dropping a ceramic phone and having not just the screen but the casing shatter, especially if it lands on its edge, says Robert Ritchie, a materials scientist and mechanical engineer at the University of California, Berkeley.
Without being able to get their hands on this imaginary phone, some ceramics experts are more optimistic. Desiderio Kovar, a mechanical engineer who studies ceramic materials at the University of Texas at Austin, says zirconia-based ceramics can be quite tough with the right design. He notes that at one time ceramic hammers were in production. “Whether an object will break or not depends not only on the material and the force that is applied, but also on the design and geometry of the part,” he says.
Apple’s patents suggest the company has given this careful consideration. One suggests that they may have made the watch more shatter-resistant by developing manufacturing processes to remove air bubbles from the material. The more perfect and uniform the ceramic, the fewer vulnerabilities it has to cracking.
Even with great design, the inherent properties of ceramics will remain, says Ritchie. “A ceramic watch will never be as resistant to fracture as a metal one—that would defy the laws of physics,” he says.
Ceramics also don’t offer a rainbow of possibilities, at least so far. The high-shine, pure-white surface of the Apple watch is a compelling aesthetic reason to use a ceramic in a watch casing, but zirconia ceramics generally come in no other colors than a dull gray. Unless the company has something else up its sleeve, choices will be limited. Faber notes that sapphire, whose chemical formula is similar to alumina’s, can display dazzling blues, ruby reds, and pinks. But this doesn’t translate to the material’s ceramic forms, which have a different crystalline structure.
Another drawback of high-performance ceramics is the manufacturing cost. Ceramics cost more not because of the materials themselves but because they are labor intensive. Molding them takes time, and getting a smooth surface requires extensive polishing. Apple seems to be touting this extra labor to market the watch as a luxury item, emphasizing that each takes days to make.
Apple is not unique in adopting ceramics for watches. Swiss watchmaker Omega, for example, sells watches with ceramic cases. That company also uses a kind of material called a metallic glass or liquid metal. Omega’s marketing materials say the alloy in its watches is three times as hard as stainless steel. Apple and Samsung both have patents pertaining to liquid metals, too. It’s possible these materials could find their way into phone cases—or that neither they nor ceramics will.
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