Whiskers: Exploring the Use of Ultrasonic Haptic Cues on the Face

Haptic cues are a valuable feedback mechanism for smart glasses. Prior work has shown how they can support navigation, deliver notifications and cue targets. However, a focus on actuation technologies such as mechanical tactors or fans has restricted the scope of research to a small number of cues presented at fixed locations. To move beyond this limitation, we explore perception of in-air ultrasonic haptic cues on the face. We present two studies examining the fundamental properties of localization, duration and movement perception on three facial sites suitable for use with glasses: the cheek, the center of the forehead, and above the eyebrow. The center of the forehead led to optimal performance with a localization error of 3.77mm and accurate duration (80%) and movement perception (87%). We apply these findings in a study delivering eight different ultrasonic notifications and report mean recognition rates of up to 92.4% (peak: 98.6%). We close with design recommendations for ultrasonic haptic cues on the face.