That foldable smartphone in your hand can withstand hundreds of thousands of folds and still work. What exactly makes this possible?
01. Why Can Glass Bend?
Ordinary glass shatters when bent, but the Ultra-Thin Glass (UTG) used in foldable screens is only 30 micrometers thick, about one-third the thickness of a human hair.
When a material is bent, the deformation is more severe closer to the outer surface. Given the same bending radius, the thicker the material, the greater the strain on the surface. Thinning the glass significantly reduces the flexibility required for bending.
But being thin is not enough. Engineers also use ion exchange strengthening technology to replace the small ions on the glass surface with larger potassium ions, forming a layer of compressive stress that squeezes inward. This layer of compressive stress is like a tight-fitting suit for the glass, making it difficult for micro-cracks to open and propagate.
02. Hinges Enable Smooth Screen Folding
Glass can bend, but how it bends and what arc it forms are determined by the hinge.
Early foldable screens used U-shaped hinges, where the screen bent sharply like a U-turn when folded, leaving a deep crease. Later, the mainstream solution switched to the water-drop hinge. The screen forms a water-drop-like curved space when folded, expanding the folding radius from 2-3mm to 4-6mm.
A gentler bend results in a more uniform stress distribution, naturally leading to a shallower crease. The hinge itself is also a piece of precision machinery.
Take the OPPO Find N6 as an example. It adopts a bionic symmetrical four-axis structure, combined with chip-level 3D printing technology, improving the flatness of key hinge components by 75%. Huawei, on the other hand, optimizes crease performance in a more compact body through the dual-track linkage design of its Tiangong hinge system.
03. Why Are Creases Becoming Less Visible?
The essence of a crease is the accumulation of irreversible deformation in the bending area of the screen. Besides the water-drop hinge dispersing stress, there are also advancements at the material level.
The Tianqiong Memory Glass on the OPPO Find N6 adopts a deep chemical strengthening process, increasing its resistance to bending deformation to 338% of that of traditional flexible glass. It can achieve 99.9% shape self-recovery after bending, allowing the crease to quickly rebound and fade when unfolded. Durability records are also being broken.
Samsung Display has raised its internal bending test standard from 200,000 to 500,000 cycles, meaning that an average user opening and closing the device 100 times a day would have a theoretical lifespan of over 10 years. Extreme testing for flagship products has reached 2 million folds.
From the 30-micrometer glass, to the hinge that expands the folding radius from 2mm to 6mm, and then to the self-healing coating. The ability of foldable screens to fold relies not on a single magical material, but on the result of glass, hinges, and coatings simultaneously approaching the limits of engineering.