We introduce FingerT9, leveraging the action of thumb-to-finger touching on the finger segments, to support same-side-hand (SSH) text entry on smartwatches. This is achieved by mapping a T9 keyboard layout to the finger segments. Our solution avoids the problems of fat finger and screen occlusion, and enables text entry using the same-side hand which wears the watch. In the pilot study, we determined the layout mapping preferred by the users. We conducted an experiment to compare the text-entry performances of FingerT9, the tilt-based SSH input, and the direct-touch non-SSH input. The results showed that the participants performed significantly faster and more accurately with FingerT9 than the tilt-based method. There was no significant difference between FingerT9 and direct-touch methods in terms of efficiency and error rate. We then conducted the second experiment to study the learning curve on SSH text entry methods: FingerT9 and the tilt-based input. FingerT9 gave significantly better long-term improvement. In addition, eyes-free text entry (i.e., looking at the screen output but not the keyboard layout mapped on the finger segments) was made possible once the participants were familiar with the keyboard layout.

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Co-authors: Pui Chung Wong, Hongbo Fu