Apple is clearly working on solving one of the knottiest of problems with foldable phones, that of hinge wrinkle. When you have a screen that crosses the fold of the phone, the screen can show wear, like you might see on the spine of a well worn paperback book, or if you folded and unfolded a piece of paper.

From Patently Apple:

A new patent application from Apple published by the U.S. Patent Office shows that Apple is working on a method to keep the fold area warm as a cold display could cause problems when folding.

Specifically, Apple notes that a folding device may have a hinge that allows the device to be flexed about a bend axis. A display may span the bend axis. To facilitate bending about the bend axis without damage when the display is cold, a portion of the display that overlaps the bend axis may be selectively heated.

Interesting solution. I do think the hinge wrinkle problem is a must solve for Apple. If I unfold my phone, a wrinkle, however slight, in the middle of the display, will kill the illusion of a single unbroken screen.