In collaboration with the Hasso Plattener Institute in Potsdam, Germany, Microsoft R&D argued that the key to touch-enabling very small devices is to use touch on the device backside. In order to study this, they have created the 2.4” prototype device shown here.
In a user study, participants completed a pointing task successfully across all display sizes when using a back-of device interface. The touchscreen-based control condition, in contrast, failed for screen diagonals below 1 inch, because the user’s fingers occlude contents and prevent precision.
The project webpage is here, including a paper (PDF) submitted to the Computer and Human Interaction conference.