Usability Evaluation of the Touch Keys for the Smart Watch

The smart watch is the most popular wearable computing device because it takes a form of wristwatch. Many smart watches have adopted the touch screen interface due to the limited size of display. This paper focuses on touch key size and spacing that affect the usability about the touch key of smart watch. The experiments were made for four touch key sizes (width×height; 5×5, 5×7, 7×5, 7×7mm) and nine touch key spacing (vertical× horizontal; 0×0, 0×1, 0×3, 1×0, 1×1, 1×3, 3×0, 3×1, 3×3mm). The completion time, error rate, control discomfort and identification discomfort were measured. The touch key size 7×7, 7×5 and the touch key spacing 3×3, 1×3 provided the best results in terms of the completion time and the control discomfort, while the square touch key (7×7, 5×5) provided the best performance for the error rate measure. The result of this study can help ergonomically design the touch interface of the smart watch. †