Why the iPhone Duo's hinge may be cracking its foldable screen

Within hours of Apple's foldable smartphone, the iPhone Duo, going on sale last Friday, social media users reported that the inner screen of some brand-new units was already damaged. Photos show a crack or defect in the middle of the screen above the hinge, with lines on the right side of the display. On Monday, Apple acknowledged an "issue" and said it would replace damaged phones, without saying how many broken units have been reported. It matters because this is the first generation of the device and the reports raise questions about the durability of Apple's foldable design.

The likely cause

Shahram Mokhtari, lead teardown technician at repair-guide company iFixit, has taken apart the iPhone Duo. He told The Verge the cause is probably the hinge, a system of gears, springs and joints that lets the phone close flat while giving the screen room to bend more gently, so that a deep crease does not form.

At the problem spot, the flexible inner screen appears to press against a part of the hinge. Mokhtari says the screen is "extremely sensitive" and would break if poked at the edges with a sharp tool. In photos of damaged phones shared online, the damage often centers on a black spot, which he says is where metal hits the screen.

iFixit's teardown shows that the hinge's center support bar makes room for a crossing flex cable, creating several edges. The bar may not always drop low enough when the screen folds, possibly creating a stress hot spot between the flat bar and the bent screen.

User reports

At least one user with a broken screen said they "felt something around the internal hinge" and kept opening the phone, then heard an "audible crack" as the screen broke. YouTuber CuriousHagi, who covered a Duo in dirt for a durability test, recorded something similar. In his teardown video, a hinge part connected to the central bar had snapped.

Apple and expert views

Apple says only a "small number" of units are affected. Mokhtari says he does not know the numbers and suspects Apple knows more than it says. He expects some foldable screens and hinges to fail because they are delicate. Apple is not recalling the phones, but if similar failures continue in three months, he says, the problem would be more widespread and a recall could follow. He expects Apple to redesign the faulty part in the next generation, and notes that most people appear to be using their phones without problems.