This is how the iPhone 6s 3D Touch sensor works

A new teardown published on iFixit, which focuses on the display of the iPhone 6s, has revealed the components that are thought to provide its 3D Touch feature.

3D Touch allows the iPhone’s touchscreen to recognise pressure, with Apple using it to offer various shortcuts in apps or on the home screen.

After prying away the front panel of the display, iFixit discovered a second layer of sensors.

These looked like capacitive sensors, and it is believed they are responsible for enabling 3D Touch on the iPhone 6s.

iPhone 6s capacitive 3D Touch panel under a reflective film.

The discovery was surprising, as Apple had stated 3D Touch worked through sensors that were integrated into the backlight.

According to the iFixit guide, each gold rectangle on the pictured panel is a single plate of a parallel plate capacitor.

Each box has a tiny trace, with the dark areas being collections of many traces, running back to the control chip – which the teardown technicians said they found on the back of the panel.

In a parallel plate capacitor, capacitance is inversely proportional to distance. A shorter distance means greater capacity for charge on the plate.

iPhone 6s panel of parallel plate capacitors.

iPhone 6s back of 3D Touch panel.

“Apple worked closely with Corning, the makers of Gorilla Glass, to develop a pliable glass for the new iPhone’s glass cover,” said iFixit.

When you press down on the glass, it bends very slightly at the point of contact, shortening the distance between your finger and the corresponding capacitor plate in the array beneath the display.

This registers a push, rather than a touch, and the chip would measure a flow of current to the sensor board.

iPhone 6s 3D Touch panel.

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