// HACKER NEWS — CYBERSECURITY
Let’s take apart your phone
Run your finger across a window. Smooth, but it drags. Now do the same on your phone. Your finger glides.
The difference is a non-stick coating one molecule thick, and every time you touch the screen a little of it wears away.
Like a non-stick pan, the screen is coated with fluoropolymers, chains of carbon atoms with fluorine attached instead of the usual hydrogen.
The carbon-fluorine bond is incredibly stable, giving the coating very low surface energy: oily fingerprints wipe away, and your thumb gets that gliding feel. It also explains why a phone left face-down on the faintest slope will attempt escape.
The first iPhone Steve Jobs revealed on stage had a plastic screen. In the months before shipping, he found the keys in his pocket had scratched the prototype and he insisted on a last-minute upgrade.
The chemically strengthened glass he demanded is seven times stronger than normal glass and quickly became the industry standard.
Normal glass, like bottles and windows, is made from silica. Smartphone glass has aluminium woven into the silica network, stiffening the structure and helping it resist cracks.
Sodium ions are also added to the mix and sit in the gaps of the silica-alumina grid. The finished sheet is dipped into a 400°C potassium bath. The small sodium ions swap places with large potassium ones, squeezing into the structure, compressing the surface.
When an impact occurs, a crack must first push through this compressed layer.
Your finger is tracked by capacitive touch, shown live at the bottom.