Is Microsoft secretly working on the return of its Surface Duo folding smartphone? It’s possible, as a recently filed patent shows it’s still coming up with ideas for hinges that are the key to making foldables work. The unusual design of the hinge, and the way it’s illustrated in the patent, makes it different than what we expect from Microsoft and foldables in general.

The majority of folding smartphones use a “water drop” style hinge, where the flexible screen forms a water drop shape at the point where it’s folded to improve durability and minimize any crease, but Microsoft’s patent doesn’t seem to include this familiar design. Instead, the hinge appears to use different “sub assembly” sections that slide and flex to facilitate the movement of a flexible screen.

It’s a different approach to the Surface Duo and Surface Duo 2, which had two separate screens attached to a central hinge mechanism, and more like the single screen system seen on phones like the Samsung Galaxy Z Fold 6 and the OnePlus Open. In a further departure from the Surface Duo design, the patent illustrates the hinge inside what appears to be a compact foldable device similar to the Samsung Galaxy Z Flip 6 and Motorola Razr 2024.

However, while we’d love to see a new Surface Duo, a smartphone may not be the only device Microsoft has in mind for its hinge. Digging into some of the wording used in the patent, it specifically mentions “folding smart phone devices,” but also mentions “computing devices that include first and second device portions that are coupled at a hinge assembly.” This sounds less like a phone and more like a laptop, where Microsoft’s Surface range has found more success.

However, the patent talks about how foldable smartphpones have been hindered by reliability issues, and how buyers prefer thinner devices over thicker ones. Its patented hinge is designed to address both these issues. While it does seem to suggest the hinge may be suitable for laptops, the wording leans more into its use on smaller devices, so it may simply be covering all its bases for the purposes of the patent.

It’s not the first hinge patent filed by Microsoft either, as in 2019 it had the idea of filling a hinge with liquid or gas to improve durability, and in 2022, it came up with a method where it could be possible to fold a single screen both inwards and outwards, something it revisited again in 2023. The Surface Duo 2 was released in 2022, and software support ended for it in late 2024.