Apple's long been rumoured to be working on a foldable iPhone, and now we have new leaked information about the device. As per a new report, Apple is reportedly testing a colour E-Ink display that would be used as an external screen on its upcoming foldable device. 

This information comes courtesy of noted Apple analyst Ming-Chi Kuo. In a tweet, Kuo claimed, “The colour EPD [Electronic Paper Display] has the potential to become a mainstream solution for foldable devices’ must-have cover/second screen thanks to its excellent power-saving.”

Apple is testing E Ink's Electronic Paper Display (EPD) for future foldable device's cover screen & tablet-like applications. The color EPD has the potential to become a mainstream solution for foldable devices' must-have cover/second screen thanks to its excellent power-saving.

As Kuo notes, this display will be used on the secondary screen of a foldable phone which makes a lot of sense as this screen technology is designed to look like paper, and to be incredibly low-power. Currently, smartphone makers such as Samsung, Oppo and Xiaomi use OLED displays for their secondary displays. These displays boast high refresh rates and also high resolutions, but end up consuming a lot of power. 

While we're not sure which Electronic Paper Display will be eventually used on the device, there's a chance that Apple uses E Ink's Gallery 3 display which offers “a full-colour gamut” through a four-particle ink system. Gallery 3 also offers a resolution of 300ppi.

But regardless of the panel the company uses for the front display, the main attraction of the foldable phone will be the primary panel. For now, there is no concrete information about it. However, we expect news about it to make it to the web in the coming weeks and months.