Designing a 2 × 2 spatial vibrotactile interface for tactile letter reading on a smartphone

Abstract

In this paper, an eyes-free tactile reading system on a smartphone is proposed. This system adopts 2 × 2 flat vibration motors that are attached to the back of a smartphone, and a spatial tactile feedback will be generated and applied to the palm while the user holds the device. The tactile reading of 26 English letters was designed using spatial vibration codes. The hieroglyphs of English letters and their order of writing strokes were borrowed to minimize the tactile code learning curve for users. Numerous user experiments were conducted to tune important design parameters, such as distance between motors and vibration times. Results showed that a 3-cm distance between motors and a 200-ms vibration time are appropriate for designing an efficient system. The accuracy of tactile letter reading was 84.6%, time was 976.9 ms per letter, and the system can provide an efficient tactile reading technique for users in an eyes-free interaction.