When Apple launched the iPhone in 2007, they also introduced the modern multi-touch system in phones. It has later become a standard in handheld devices. With iPhone 6S and 6S Plus, Apple is introducing "the next generation of multi-touch". 3D Touch can detect how hard you press the screen and is combined with a haptic feedback system.
3D Touch on iPhone 6S & 6S Plus
Touch technology today uses swipes and pinches with one or more fingers. Apple believes that there is a need for 3-dimensional levels; levels that can detect how hard you press. That is why they have created 3D Touch.
3D Touch is an extension of Force Touch, which was first integrated into Apple Watch. The new system does not rely on "long" presses, which is utilized by many phones today, but can physically detect how hard you press the screen.
Apple has redesigned and optimized the user interface in iOS 9 for the new functionality. On the home screen you can quickly access additional features by pressing harder on the camera, maps or music icons. 3D Touch can also be utilized inside apps, and the tools have been made available for developers immediately. Apple imagines that you can use it in games, drawing, for shortcuts and more.
3D Touch is not limited to only one level of force. The system can distinguish between soft and hard presses. A soft press will typically give you a “preview” of an email, a photo or a message. A harder press will access the content. Apple demonstrated this distinction in the Messages app where a soft press on an address or date gave additional information without closing the message app.
3D Touch is integrated deep into the display itself. The capacitive sensors in the backlight can detect and measure the tiny distance between the front glass and backlight unit when you press the screen. This makes it possible not only to detect the level of pressure but also the exact location of the touch screen. With Force Touch on Apple Watch pressure is registered for the entire display, and herein lies the difference between 3D Touch and Force Touch. 3D Touch is possible because Apple uses in-cell touch technology.
The system furthermore uses haptic feedback to make you feel those hard presses. Apple’s so-called "Taptic Engine" is integrated behind the screen. Apple explains that traditional systems need “ten oscillations" to achieve full vibration whereas the new Taptic Engine can reach full vibration in the first cycle. The engine can therefore vary the degree of haptic feedback by milliseconds, depending on where and how hard you press.