The iPhone Duo developing a crease over time is inevitable as the tides, and a matter of physics and engineering. Here's how and why that crease develops, and what Apple has done to mitigate it. In the run-up to Apple's folding iPhone, there was a lot of chatter about how Apple has "solved the smartphone crease." It's always been a silly topic, as there is no solving it, there is only postponing it.

It's an engineering problem on top of a physics problem. The physics are immutable. What can be controlled is engineering tolerances, coupled with precise engineering, tailored to known stress points.

It's about working around the issues of a hybrid screen, with the properties of both glass and plastic. Plastic OLED and very, very thin glass layers on its own, the OLED screen substrate is not rigid, and can bend and flex because it is essentially plastic. It too can break and tear, and is very soft.