From your finger's angle of attack,to gestures like twists, researchers have developed algorithms to manufacture any touch screen smarter.
When you touch your iPhone screen, or it basically sees a few dark spots with no other context. From that alone,it's brought us landmark interactions like the swipe and pinch-to-zoom. But to enact more, Apple had to rebuild its own touch screen, and adding the pressure sensitivity of 3D Touch.
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Source: fastcompany.com