Just last month we heard that Apple might not launch a folding iPhone until 2020, but we may already have an idea of the form it will take, as the company has published a patent housing some clues.
This would potentially be achieved using an optically clear flexible adhesive and a shape memory alloy or amorphous metal.
More specifically, Liquidmetal is mentioned as a possible material, which would make sense since Apple has long had exclusive rights to the amorphous material in consumer electronics, yet so far has done little with it.
OLED's days might already be numbered
With Apple only just now moving to OLED for the iPhone X we wouldn’t expect another change in technology any time soon, but if a foldable iPhone doesn’t launch before 2020 it’s possible that micro-LED could be used.
However, if we really are waiting that long for a folding iPhone then Samsung could have a major head start, as it’s possible that the 'foldable' Galaxy X will launch next year.