Edge flows: Improving information transmission in mobile devices using two-dimensional vibrotactile flows

Vibrotactile flows refer to vibrotactile sensations that move continuously on the surface of a mobile device. They have been studied to render one-dimensional illusory movements using two actuators. In this work, we extend the dimension of vibrotactile flows to two dimensions by means of edge flows-vibrotactile flows that rotate along the edges of a rectangular mobile device, rendered using four actuators placed at its four corners. We designed 32 edge flows and carried out a longitudinal user study in order to measure the information transmission capacity of edge flows, while looking into the effects of practice and correct-answer feedback on the identification accuracy of edge flows. Results showed that the information transmission capacity of the edge flows was 3.70 bits, which is greater than for most previous studies; that some extent of practice is required for robust identification, but it can take place quickly; and that correct-answer feedback is advantageous but its degree of improvement was less than that of repeated practice. Our findings can contribute to enlarging the design space of tactile stimuli for robust transmission of abstract information to mobile device users.