How Foldable Phone Screens Work—and Why They Crease

A Screen That Bends Without Breaking

Smartphones with screens that fold in half sound like science fiction, yet tens of millions ship every year. The foldable phone market is projected to grow 30 percent in 2026 alone, according to IDC, with research firm Omdia forecasting an even steeper 50 percent jump. Behind the trend lies a stack of material-science breakthroughs that allow glass, circuitry, and light-emitting pixels to survive hundreds of thousands of bends.

Why OLED Is the Only Option

Every foldable phone on the market uses an OLED (organic light-emitting diode) display. Traditional LCD screens need a rigid backlight layer that cannot flex, but OLED pixels generate their own light when current passes through thin organic films. Remove the backlight and you remove the stiffest component in the stack, making the entire panel thin enough to bend.

Manufacturers deposit these organic layers onto a polyimide plastic substrate instead of conventional glass. Polyimide is heat-resistant, chemically stable, and — critically — flexible. The result is a display panel roughly as thick as a sheet of paper that can curve around a radius of just a few millimeters.

Ultra-Thin Glass: Strength Without Stiffness

Early foldable phones covered their screens with plastic film, which scratched easily and felt cheap under the finger. The industry's answer is ultra-thin glass (UTG) — real glass polished or chemically thinned to about 30 micrometers, roughly half the width of a human hair.

German glassmaker Schott and South Korea's Samsung Display are the leading UTG suppliers. The glass undergoes a chemical strengthening process in which its surface is infused with larger ions, creating compressive stress that resists cracking. Samsung Display says its latest UTG panels have survived 500,000 fold cycles in durability tests — the equivalent of opening and closing a phone more than 100 times a day for over 13 years.

The Hinge: Engineering in Miniature

A foldable phone's hinge must do several things at once: hold the device rigid when open, allow a smooth fold, and create a gap just large enough that the screen is not crushed at the bend point. Modern hinges use dozens of interlocking gears, cams, and rails machined to micrometer tolerances. Some designs, like Samsung's Flex Hinge, use a sweeper mechanism that blocks dust and debris from entering the fold — particles that could puncture the delicate display layers from behind.

Why the Crease Won't Disappear Easily

Despite all this engineering, almost every foldable phone shows a visible crease — a faint line or depression running down the centre of the screen where it folds. The crease forms because even ultra-thin glass and polyimide substrates accumulate permanent deformation over repeated bending cycles. Temperature changes make it worse: polymers stiffen in the cold, deepening the fold mark.

Eliminating the crease is widely regarded as the industry's hardest remaining challenge. Apple, which is developing its first foldable iPhone, has reportedly targeted a crease depth below 0.15 millimeters — roughly one-quarter the depth of competing devices — by using laser-drilled microstructures that distribute bending stress more evenly across the fold zone. The technique raises component costs significantly but could set a new benchmark for display quality.

What Comes After the Fold

Foldable screens are only the beginning of flexible display technology. Samsung and LG have demonstrated rollable prototypes where a screen unspools from a housing like a scroll, and stretchable panels that can expand in area by up to 50 percent. Researchers at IEEE Spectrum note that stretchable displays could eventually wrap around curved surfaces — wrists, dashboards, even clothing.

For now, the foldable category is entering a pivotal phase. With the global market valued at nearly $39 billion in 2026 and forecast to exceed $110 billion by 2031, the engineering race to build a crease-free, durable, pocket-sized folding screen is far from over — and its outcome will shape how we carry and use technology for decades to come.