We describe the preliminary results from an experiment investigating the perceived intensity of modulated friction created by electrostatic force, or electrovibration. A prototype experimental system was created to evaluate user perception of sinusoidal electrovibration stimuli on a flat surface emulating a touch screen interface. We introduce a fixed 6-point Effect Strength Subjective Index (ESSI) as a measure of generic sensation intensity, and compare it with an open magnitude scale. The results of the experiment indicate that there are significant correlations between intensity perception and signal amplitude, and the highest sensitivity was found at a frequency of 80 Hz. The subjective results show that the users perceived the electrovibration stimuli as pleasant and a useful means of feedback for touchscreens.
Wijekoon, D., Cecchinato, M.E., Hoggan, E., & Linjama, J. (2012). Electrostatic modulated friction as tactile feedback: intensity perception. In Haptics: Perception, Devices, Mobility, and Communication (pp. 613-624). Springer Berlin Heidelberg.