After years of speculation, the time had finally come yesterday: Apple introduced a new iPhone with a foldable screen. Competitors such as Samsung, Oppo and Google have previously launched several similar models. Now it’s Apple’s turn, with the iPhone Duo.
But what actually is a foldable screen, how does it work, what are the advantages and disadvantages. We will explain that in this article.
10 Ultra-thin layers
The iPhone Duo’s foldable screen (7.6 inches) has a total of 10 ultra-thin layers, including a nano-textured coating of a special polymer that Apple says is up to 40 percent stiffer than “other materials used in the industry,” presumably meaning other foldable devices.
Both the indoor and outdoor displays of the iPhone Duo have a peak brightness of up to 3000 nits and ProMotion up to 120 Hz. This allows you to view the content on the screen even in full sunlight.
Apple uses multi-layer lamination, which is a construction in which multiple ultra-thin layers (glass, OLED, adhesive, support materials) are laminated on top of each other into one flexible whole, a layer stack.
On the iPhone Duo, this is designed so that the layers can slide slightly relative to each other during folding, so that the bending stress is not concentrated in one place but is distributed over a larger surface. Distributing the bending stress prevents the need for a sharp fold in the screen, which may become visible over a longer period of time. The hinge of the device also plays a major role in this.
Titanium hinge
The iPhone Duo’s hinge is one of the most complex parts: a titanium hinge with more than 100 precision parts, specially designed to help the screen fold smoothly and remain completely flat when open.
The housing and parts of the hinge are made of grade 5 titanium, while the hinge cover consists of 3D printed titanium from 100% recycled material with a micro-blasted finish. Internal support ribs and ceramic fiber inserts in the antenna split provide additional reinforcement, making the construction up to 3x stronger than standard grade 5 titanium.
The Duo’s hinge is designed to make opening and closing feel controlled, smooth and stable. Apple uses a so-called variable torque profile for this: the resistance of the hinge adjusts during movement, so that the device does not open too loosely or too stiffly. This makes every position feel natural and precise.
When closing, a built-in magnet array helps the device click closed firmly and in a controlled manner. The magnets ensure that the Duo remains securely closed when you are not using it.
When the device is fully unfolded, the hinge supports the center of the screen. This way the display remains flat and does not sag at the fold line. This provides a cleaner image and a more stable user experience.
In addition, the hinge makes it possible to partially open the Duo. This allows the device to stand independently on the table, for example for FaceTime, watching videos or use in a kind of laptop mode. The hinge thus combines smooth movement, firm closure and stable support in different usage positions.
Layer by layer
In addition to the layer stack, the hinge is also an essential part of a foldable screen. The different layers of the layer stack all have their own function. This includes a layer containing the physical screen and a special layer for extra strength. The 10 layers of the iPhone Duo from the top layer to the bottom layer consist of:
- Nano-texture top layer (anti-glare)
• A microscopically patterned surface layer that scatters light instead of reflecting it.
• Goal: less reflection and making the fold line visually less noticeable. - Top high-strength glass layer (UTG-like)
• An ultra-thin, flexible glass layer that makes the screen touchable and scratch-resistant.
• Works as a protective “cover” for the OLED underneath. - Optically clear glue / viscoelastic adhesive (top)
• Transparent adhesive that connects the top glass layer to the OLED.
• Behaves somewhat “softly” so that the layers can slide microscopically during folding. - OLED panel (luminous layer)
• The actual Super Retina XDR‑OLED that produces the image.
• Is “encapsulated” between the two layers of glass, so that the mechanical stress is largely absorbed elsewhere. - Optically clear glue / viscoelastic adhesive (below)
• Another adhesive/buffer layer under the OLED, symmetrical at the top.
• Helps distribute bending stress evenly. - Lower high-strength glass layer (UTG-like)
• A second ultra-thin glass plate under the OLED.
• Together with the top glass layer, this forms a dual-UTG-like sandwich around the OLED. - Custom polymer/composite layer
• A special polymer layer that Apple describes as ~40% stiffer than the industry standard.
• Strengthens the structure without adding much thickness or weight. - Carbon‑fiber support plates
• Light, stiff plates that give the panel a stable base.
• Ensure that the screen does not “sag” or deform locally. - Titanium base plate
• A thin titanium plate as a structural backbone under the entire screen.
• Increases durability and helps mechanically support the folding zone. - Additional adhesives / buffer layers
• Mounting layer to place the screen in the device with protection against the underlying components.
FaceTime camera behind the screen
For the first time, Apple has incorporated the FaceTime camera into the screen. The camera is located behind the 7.6-inch OLED inner screen, approximately in the middle of the top half of the screen on the right.
When the camera is not in use, it is virtually invisible: the pixels above the lens continue to show an image. Only during FaceTime calls or when taking selfies is a small, darker window activated locally, so that the camera can see through the screen. Apple has positioned this in such a way that it is barely noticeable during video calls.
However, from different viewing angles, the circle of the FaceTime camera is visible in the normal screen display, because the reflection is slightly different.
Is the fold of the iPhone Duo visible or tangible?
The crease in the screen is virtually invisible when the Duo is fully opened. Moreover, it seems to be barely noticeable, as the hinge pushes and holds the screen tightly. According to the first testers, you hardly feel the crease when you run your finger over the screen.
The technology behind the screen helps to limit the burden. Multi-layer lamination with viscoelastic adhesives allows the different layers to move slightly relative to each other, so that mechanical stress is less concentrated on one narrow line.
In addition, iOS takes the folding zone into account. The system can subtly shift content where necessary, so that interactions around the fold remain reliable and the fold does not become distracting.
During normal use, the fold of the iPhone Duo is barely visible. Time will tell whether this becomes more noticeable after thousands of folding movements and prolonged use.
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