Back-of-Device Interaction based on the Range of Motion of the Index Finger

We show a back-of-device (BoD) interaction based on the range of motion of the index finger to improve the usability of a touchscreen mobile device held in one hand. To design this interaction, we conducted two experiments to investigate the range of motion of the index finger on the back of mobile devices. On the basis of those results, we designed a prototype system that has a hole in the back, where users perform our BoD interaction by covering the hole with their index finger. This design provides them with the tactile feedback provided by a hole, and allows users to naturally control the front and back simultaneously.