My coworker Mat Honan (you know, the guy who got hacked) experienced a supremely unpleasant surprise at CES this year.
The week before, Mat had ponied up for a chic new Moto X with a bamboo back. Then, at the show, he did something we've all done hundreds of times: he stashed his brand new phone in his pocket. He slipped it into his back pocket as he was getting out of a cab. It turns out he had a thumb drive in the same pocket. No big deal, right? Wrong. When he pulled the phone out minutes later-before sitting down again-he found the screen split into hundreds of tiny glass daggers. It had been subjected to nothing more than the pressure of a thumb drive against it.
'I'm pissed that my brand new phone that I paid my hard-earned money for was so vulnerable to something I literally couldn't detect,' Honan lamented on our live blog after the incident. 'Like; I had no idea anything happened. It just smashed. Booooooooo.'
It's a symptom of the times. Smartphone makers are increasingly incorporating unusual and inventive materials in their super-slim handsets to set them apart from the mass of black, white, and silver slates. Motorola used Kevlar on the Droid Razr for a carbon fiber-like look that was not only super light and thin. Apple's iPhone 4 stunned us with its svelte glass. The Nokia Lumia series sported lightly textured polycarbonate in bright, fun colors. Several iPhone models have employed aluminum for a sturdy metallic sheen.
Each material has pros and cons in terms of personality and durability. Durability, though, is important not just for making sure the phone properly weathers the bumps and scratches of daily use, but also because it adds some structural integrity to the device.
It's actually not the choice of materials alone that makes a handset more or less prone to damage - screen breakage in particular. It's the structural design in general. It's what's beneath that candy-colored shell that really counts.
'The casing should have higher stiffness or resistance to bending,' says Ronald Gronsky, UC Berkeley's Arthur C. and Phyllis G. Oppenheimer Chair in Advanced Materials Analysis. 'This keeps both the internal electronics and the glass touchscreen intact.' Gronsky says metallic alloys are best at this, followed by wood, then polymers. He notes that the casing materials must also be kept very thin in order to make sure the device is slender enough to fit in our pockets or be wielded one-handed.
But it's not the choice of materials alone that makes a handset more or less prone to damage-screen breakage in particular. It's the structural design in general. It's what's beneath that candy-colored shell that really counts.
'The Samsung Galaxy S3 and S4 do just as well in break tests as the iPhone, and they have a plastic back just like the Moto X,' iFixit's Kyle Wiens told WIRED. If you take the rear casing off the Galaxy phones, you can make it flex and bend, even though the iPhone 5s's aluminum rear barely budges in the same scenario.
A display's tendency to break has a lot to do with the structural and torsional rigidity of the device, Wiens says. Glass is not flexible, so if you can twist or bend your phone, it's more likely that the pressure caused by that motion could crack the screen.
In the case of the Galaxy phones, for example, Samsung has increased the overall rigidity of the device by using a plastic frame that goes all the way around the inside rear of the handset. This frame cradles the removable battery and protects the phone's delicate circuit boards. The handset is just as stiff with the rear case as it is without it.
The iPhone 5c, with a case is crafted from one of the stiffest polycarbonates available, uses a different method to keep the device sturdy: a steel-reinforced frame (that doubles as antenna) inside the plastic casing. This gives provides rigidity on par with its aluminum-clad siblings, the iPhone 5 and 5s.
The Moto X has a less substantial mid-frame, as this interior buttress is called. Thus, it is less rigid-not a good thing for a device with other components aren't designed to bend. However, this less substantial mid-frame shouldn't have been a problem. There are other ways to ensure a device stays stiff and unyielding. The Moto X, instead of using a plastic or metal interior, uses another popular material for adding rigidity to a device: Glue.
Used properly, glue should provide the same amount of inflexibility as metal frames. In fact, many devices use glue for structure and it works just fine. The iPad Air, for instance, uses a lot of glue - it provides internal support but doesn't take up a lot of space (it also makes things very difficult to repair). The iPhone 5s, instead of using a plastic battery housing like many phones, uses some glue to keep the battery in place. In the case of the Moto X though, it does not appear that the glue is giving the phone the rigidity it actually needs, at least in situations where torsion may be applied.
But of course, the factor that's most to blame for screen breakage is our quest for ever-thinner mobile devices.
Advancements in alkali-aluminosilicate glass technology mean that we can have glass touchscreens that are just as strong as previous versions, but much thinner, says IHS supply chain analyst Kevin Keller.
'If a cover glass were to be manufactured using the latest Gen 3 Gorilla glass (or Asahi Dragontrail, or Schott Xensation) but at a thickness more typical of the Gen 1 Gorilla glass designs of several years ago (say, 0.8mm or so), this would be virtually indestructible,' Keller tells WIRED. Instead, we've kept display glass at that same hardness level, but made them thinner, so they're just as likely to crack under intense applied pressure, he says.
Keller also notes that while torsional forces can be problematic, it's impact forces - when you drop a phone, or when you drop something on your phone - that your handset is most vulnerable to. So perhaps it wasn't that thumbdrive forcing my coworker's Moto X to bend in an unnatural way that caused the screen to break, but the initial force of shoving the phone into the pocket, straight onto a metal thumb drive.
However it happens, a cracked smartphone screen sucks. But at least you can rest easy knowing that merely swapping out the rear case on your device isn't going to make it significantly more susceptible to a break.
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