Apple ran a graphite pipe through the iPhone Duo's hinge to cool it

Apple’s first foldable has the heat problem every foldable has: it’s thin when it’s open, and its thickness doubles when you close it. Apple’s engineers told PCMag that their fix was to route a flexible graphite pipe through the hinge itself, so heat can move between the two halves of the phone. I love that the hinge, the part everybody worries about on a folding phone, got a second job.

Banafsheh Barabadi, Apple’s senior manager of thermal product design, called it “one of the most technically challenging aspects of our design.” Moving heat across both halves gives the phone more surface area to get rid of it, PCMag reported. She said the thermal and mechanical teams had to engineer the part together, because it has to survive “many hinge cycles” while still carrying heat and holding together for the life of the phone.

The Duo gets its own cooling layout inside, too. PCMag reported its vapor chamber is thinner than the one in the iPhone 18 Pro and floats in the middle of the phone instead of serving as part of its frame. 9to5Mac, writing up the same interview, noted that the Duo’s version of the A20 Pro chip has a second display engine so the inner and outer screens can run at the same time.

The performance numbers are Apple’s. Barabadi said the latest iPhones achieve “35% higher sustained GPU performance than iPhone 17 Pro,” and PCMag said it hasn’t tested the A20 Pro in the Duo yet but expects to in the coming weeks.

If you’ve ordered one, I’d wait for those reviews before counting on it for long gaming sessions or long video recordings, the sustained workloads where Barabadi said the gains show up. And since the pipe lives in the hinge, I’d want any review that folds the phone a few thousand times to check heat as well as wear.

It’s a clever trick. Now the hinge has two jobs to survive.