The technology behind foldable smartphones represents remarkable engineering achievements. This article explains the scientific principles that make foldable displays possible.

Flexible Display Technology

Foldable displays use OLED (有機 light-emitting diode) technology, which is inherently flexible because the light-emitting layers are thin 有機 compounds deposited on a flexible substrate rather than rigid glass. The display consists of multiple layers: a flexible polyimide or ultra-thin glass (UTG) substrate, thin-film transistors (TFT) that control individual pixels, 有機 light-emitting layers for each color (RGB), and encapsulation layers to protect from moisture and oxygen.

The key innovation is replacing the rigid glass substrate used in traditional displays with a flexible polymer or ultra-thin glass that can bend to a radius of 1-5mm without breaking.

Ultra-Thin Glass (UTG)

Samsung’s foldables use ultra-thin glass developed by German company Schott. This glass is only 30 micrometers thick—about one-third the thickness of a human hair. At this thickness, glass becomes flexible while maintaining scratch resistance superior to plastic. The glass is manufactured through a special ion-exchange strengthening process similar to Gorilla Glass but adapted for extremely thin substrates.

Hinge Engineering

The hinge is the most mechanically complex part of a foldable phone. A modern hinge contains 60-80 individual components, including multiple gears, springs, and 支援 brackets. The hinge must enable smooth folding, maintain the display at precise angles (including partial Flex Mode positions), prevent dust ingress through brush seals, and 支援 the display evenly to prevent 壓力 concentration.

Samsung’s dual-rail hinge structure uses two interlocking gear mechanisms that move in perfect synchronization, ensuring the display folds evenly without shearing forces.

Crease Physics

The display crease is an inevitable consequence of folding a flat surface. When a display folds, the inner surface compresses while the outer surface stretches. The crease forms because the display material must accommodate these opposing forces. Manufacturers minimize the crease by using a teardrop-shaped folding mechanism that creates a larger fold radius (reducing 壓力), optimizing the UTG thickness and polymer layer composition, and using shape-memory materials that help the display return to flatness.

Summary

Foldable smartphone technology combines flexible OLED displays, ultra-thin glass, and precision hinge engineering. Understanding these scientific principles helps appreciate the engineering challenges manufacturers have overcome to bring these devices to market.