The iPhone Duo's inner screen folds in the middle, and Apple's own wording is that its design minimizes the crease, not that it removes it. Apple has also confirmed an issue affecting the inner display on a small number of Duo units, and it says owners who see a problem should contact AppleCare for a replacement.
Apple says the crease is minimized
Apple uses several tricks to keep the fold out of sight. The inner display is made of layers held together with adhesives that let them glide past each other as the screen folds, which Apple says reduces stress and the crease. A matte nano-texture finish cuts glare and reflections, and Apple says it minimizes how visible the crease is. When the phone is open, the hinge supports the center of the display to hold it flat.
Apple's own FAQ asks whether the inner display shows a crease where it folds. Its answer describes a flat and smooth display with a nano-texture finish, without a plain yes or no.
What the hinge is made of
Apple says the hinge is engineered from more than 100 components to control opening and closing and support the middle of the screen, with a magnet array that holds the phone securely shut. The frame and the 3D-printed hinge cover are grade 5 titanium. Inside the screen, high-strength glass sits above and below the folding panel, with a titanium plate at the bottom. Apple's product page doesn't give a rating for how many times the phone can be folded.
Apple confirmed a problem with some inner displays
On October 26, Apple said in a statement to 9to5Mac, "We are aware of an issue impacting the inner display on a small number of iPhone Duo units. If users experience issues with their iPhone Duo display, they should contact AppleCare for a replacement." Apple also told 9to5Mac that most units are not susceptible to the issue, that affected units appear to show it rather quickly after use, and that there is no recall.
A day later, Apple published a support page for hinge problems on the Duo. It covers a phone that won't open or close completely, noise while folding, and a hinge that feels loose, bent or broken. The page says there are no diagnostics or software fixes for hinge issues, so restarting or updating won't help. If the basic checks don't solve it, the repair step is a new inner display assembly.
How to look after the hinge and the inner screen
Apple's handling guide has a few rules that only apply to the Duo. Keep sand and grit away from the hinge, and make sure the hinge is clean before you open the phone. Before closing it, clear anything off the inner screen, because folding keys or coins inside can damage it. The inner display has a nano-texture cover layer that is part of the screen, and Apple says not to try to remove it.
Apple also says a stick-on screen protector on the inner display can make it work worse, because the screen is tuned for that built-in layer. The Duo is rated IP68 for up to 6 meters of water for 30 minutes, but Apple notes that water and dust resistance can decrease with normal wear.
Should the crease or the display issue put you off
Apple describes the crease as minimized and doesn't claim it is gone, so it is worth seeing the inner screen in a store before you buy if a fold line would bother you. On the display issue, Apple says most units are not susceptible and that affected ones appear to show it quickly, so check the inner screen closely in your first days with it and keep your receipt and return window in mind. If something looks wrong, Apple's advice is to contact AppleCare for a replacement.
For more on the phone, see our coverage of the iPhone Duo launch and of Duo stock after it sold out.
