While Apple's and Google's recent updates encourage users to spend less time looking at their phones, Microsoft's found that users "want a larger, always-on screen".
Microsoft's answer to this problem is a second-screen prototype in the form of a 3mm thick Alcantara cover with an E Ink display that runs off a Lumia 640 smartphone.
As to why Microsoft Research is using the three-year-old Lumia 640, the company was actually carrying out research into secondary displays back in 2015, the year the Lumia 640 was released.
To save time, the researchers didn't bother adding a touch overlay to the E Ink cover, but rather included five touch 'buttons' at the bottom of the display.
"The touch buttons and display connect to interface circuitry added to the rear of the phone -- a Lumia 640 -- via flat-flex cables which run through the flip cover 'hinge' along with a bend sensor," the researchers explain.
"The cover itself consists of a bezel of soft-touch fabric, which is heat-bonded to the display and to the rear surface of Alcantara using custom-made heated tooling. To reduce cost and lead time we 3D-printed this tooling in stainless steel at Shapeways."
The E Ink cover was motivated by the results of interviews where people reported wanting quicker and easier ways to access information stored on their phones. Interestingly, given the trend towards larger display phones, people reported not wanting a physically larger phone.
The five buttons on the E Ink display allow users to press and hold a button to pin screens to the display. Users can then save different items like an air ticket, a to-do list, the weather, or even Cortana to the various screens.
The researchers also detail ideas that weren't supported by a non-touch E Ink screen for dual-screen actions, such as using the E Ink display to research online while writing on the main screen, using the E Ink display as a keyboard, or editing a document across two screens.
"The users we worked with during this project were genuinely surprised to learn that a display could be integrated in such a thin form factor and without materially affecting battery life," the researchers note.
"Despite the limitations of our basic 'screen shot' experience and the lack of full screen touch interaction, anecdotal evidence from our user trials showed the value of easy access to previously stored information such as electronic boarding passes, train timetables and shopping lists."
Other contributors to the project were from Porsche, Ludwig-Maximilians-Universität, Northumbria University, and Oxford University.