ForceBoard: Using force as input technique on size-limited soft keyboard

Various typing methods of qwerty-based keyboards on smartwatches have been proposed in recent years. However, since each key can only occupy limited input space and our fingers are too big, recent solutions are mainly two-step typing methods. Users have to navigate the desired key on an enlarged keyboard, and then select the target. The two-step process is distant from our physical keyboard experiences, and requires users to frequently change the keyboard layouts. The aim of this paper is to propose a single-step typing technique that allows users to key in a character with a single touch. We introduce ForceBoard, which combines two adjacent keys into one region and uses force as selecting mechanism. By using that, it not only provides more precise selection, but also allows users to type texts without changing the visual contents of keyboard. We conducted a study comparing the performance of ForceBoard with other two state-of-the-art two-step methods, ZoomBoard and SplitBoard. Our results showed that ForceBoard outperformed ZoomBoard significantly with 30.52% on average, and was slightly better than SplitBoard. Furthermore, ForceBoard also received higher preferences on text speed and satisfaction.