Folding glass: how, why, and the truth of Samsung’s Z Flip
On February 11th, 2020, Samsung introduced the world’s first folding glass phone: the Galaxy Z Flip. Samsung declared that it had broken the laws of physics by bending glass, specifically by making “a leap from polymer screens to ultra-thin glass technology.”
Samsung made it sound like it had invented a new proprietary form of glass, and the company even dubbed it Samsung Ultra Thin Glass (UTG). “We’ve done the impossible and created ultra thin glass that folds,” the company’s presentation claimed, adding that it “protects your screen from scratches.”
Glass experts could have warned you about what happened next, when it turned out that Samsung’s supposed “leap” does use polymer and is easy to scratch after all. Samsung’s dust-resistant “fiber shield” immediately went on to fail an aggressive dust test, and the company’s claims around glass have now retreated to the ridiculous tagline “tough, yet tender.”
But Samsung didn’t lie about the primary innovation here: the Galaxy Z Flip is truly a folding glass phone. It’s just that glass is actually made by German manufacturer Schott, it’s got a soft, scratchable plastic layer up top, and — hopefully — future folding glass phones won’t require that extra protection.
To understand why, you should probably first understand how glass can fold at all.
Flexible glass is real
If I’m being honest, I’m still wrapping my head around it myself. Glass is fragile; even if you’ve somehow never broken glass yourself, you definitely know how it sounds when it shatters. It’s tough to even imagine how such a brittle material could be turned into a bendable flip phone, which is why I’m not surprised when Samsung found itself facing accusations that the Galaxy Z Flip’s ultra-thin glass might not be glass at all.
And yet the physics of folding glass is remarkably simple, according to two material scientists, as well as representatives from Gorilla Glass maker Corning and Schott itself. The short version: practically anything can be bent if you make it thin enough.
"“One of the most common misconceptions about glass is that it breaks because it’s inherently weak” — Corning"
“All the materials we know of that are very rigid can be bent to some extent,” says Schott’s Dr. Mathias Mydlak, a chemist who now leads business development for the company’s ultra-thin glass. “If you think of wood, a 2x4 cannot be bent, but if you chisel a very fine piece of it […] the same is true for glass,” he told me late last year. While a normal windowpane might not seem to bend before breaking, a thin enough ribbon of glass actually can.
When you bend a material, glass or otherwise, what you’re doing is naturally stretching the material on the outside of your bend — and even glass has some flex. “You could imagine a metallic spring between every two atoms and the spring elongating when you stretch the two atoms apart,” says Erkka Frankberg, a research fellow at Tampere University who studies unconventional forms of glass.