Bevel or Not: Identifying the Potential of Bevels for Touch Input Accuracy on Ring Device

Smart rings can serve as a wearable platform for off-device control of nearby devices. However, their thin bands lead to a small touch surface on the ring, limiting touch input expressivity and accuracy. To address this, we investigate the effectiveness of ring shapes that use beveled surfaces in addition to the flat outer surface as input surfaces. The distinct angles of the three surfaces limit touches to the intended surfaces, improving accuracy. A first study showed that with band widths of 6 mm or less, flat rings achieved low accuracy (63.8%) in distinguishing between left and right edge touches, whereas beveled and rounded rings achieved high accuracy (90.0%, 93.3%). In a second study of nine touch gestures on 6-mm rings, beveled rings outperformed the flat rings, achieving 92.9% (sighted) and 91.8% (eyes-free) with FPR $\le 1\%$. Through these investigations, we identify beveled surfaces as a promising method toward expressive, precise touch input.