A new Apple patent filing reveals the company’s research into a new kind of flexible display that uses “active fluids” to present images and information. The displays are made out of transparent shells filled with conductive fluid that responds to an applied voltage.

The patent is titled “Transparent structures filled with electrically active fluid,” and it describes a method of creating flexible displays that could be used inside things like Apple Watch straps and new biometric sensors.

The displays use a special fluid “that responds to an applied voltage by conducting current or changing crystalline structure,” Apple explains in its filing. That fluid has the ability to change state and color when a certain voltage is applied, providing feedback to the user.

One use for these displays, Apple notes, is to create intelligent bands for devices like the Apple Watch, which might display images and information — such as notifications — or change color in response to taps, gestures, presses, and swipes.

Apple also describes how the technology could be used to create robust and flexible connectors. A transparent shell filled with transparent liquid could be used to create a connector that is used at a point of high mechanical fatigue, like in the lugs of an Apple Watch.

“In one example, a smartwatch uses flexible channels filled with conductive fluid to communicate with a heart rate sensor positioned at the end of its wristband,” reports AppleInsider. 

“Fluid-filled cavities provide greater resistance against wear and tear than wires and prove more reliable than conductive fabrics like those used in iPad Pro’s Smart Keyboard.”

Apple’s patent also mentions how this technology could be used to create electromagnetic interface shielding, more attractive device antennas, cooling systems, and more. Its patent was first filed in June 2015.