This paper presents EdgeVib, a system of spatiotemporal vibration patterns for delivering alphanumeric characters on a 2x2 wrist-worn vibrotactile displays.
We first investigated spatiotemporal pattern delivery through a watch-back tactile display by performing a series of user studies. The results reveal that employing a 2×2 vibrotactile array (below Fig b) is more effective than employing a 3×3 one (below Fig a), because the lower-resolution array creates clearer tactile sensations in less time consumption.
We then deployed EdgeWrite patterns on a 2×2 vibrotactile array to determine any difficulties of delivering alphanumerical characters, and then modified the unistroke patterns into multistroke EdgeVib ones on the basis of the findings (as shown in below Fig a & b).
The results of a 24-participant user study reveal that the recognition rates of the modified multistroke patterns were significantly higher than the original unistroke ones in both alphabet (85.9% vs. 70.7%) and digits (88.6% vs. 78.5%) delivery (results shown in below Fig), and a further study indicated that the techniques can be generalized to deliver two-character compound messages with recognition rates higher than 83.3%. The guidelines derived from our study can be used for designing watch-back tactile displays for alphanumeric character output.