Researchers are proposing many approaches to overcome the usability problem of a smartwatch owing to its small touchscreen. One of the promising approaches is to use touch-sensing edges to expand the control space of a smartwatch. We considered possible interaction techniques using touch-sensing edges in combination with the smartwatch touchscreen: single-edge, multi-edge, and edge X screen (edge and touchscreen in combination). We call these techniques square watch interaction (SWI) techniques in this paper because they exploit the form factor of a square smartwatch. To explore the design space and evaluate the usability of the SWI techniques, we implemented a square smartwatch prototype with touch-sensitive edges, and conducted a series of user experiments. The experiment results showed that the SWI techniques enable precise 1D pointing and occlusion-free 2D pointing. The experiments also produced empirical data that reflect human manual skills for the edge X screen techniques. The produced empirical data will provide a practical guideline for the application of the edge X screen techniques.
The hardware was made with IR diodes and photoelectic sensors.
Possible interactions using four touch-sensitive edges of a smartwatch.
The paper is available from Science Direct.