Preliminary study on electrotactile sensitivity of the lips

The sensitivity and discriminating ability of the lower lip have been evaluated In this preliminary study. Past psychophysical studies show that the lips are highly sensitive due to their large cortical mapping, leading one to envision a wearable lip-based tactile display that is easy to use and allows hands-free operation. As lips have never been utilized for tactile display applications, preliminary study on the sensitivity and discriminating ability of the lips is conducted on five human subjects. Three stimulator arrays of different sizes are utilized to present electrotactile patterns in experiments on measurement of sensory thresholds and rating of two-line separation. Experimental results show that the lips need very low intensities for effective electrotactile stimulation. As the stimulator diameter increases from 75 μm to 1.55 mm, the average stimulation intensity at the threshold level decreases from 11.6 V to 6.6 V for the lower lip, and the percentage of correct rating of spacing between two adjacent lines increases from 47.3% to 84.8%. The preliminary study will help to understand the electrotactile characteristics of the lips and to optimize the design of an electrotactile display with geometrical parameters suitable for lip stimulation.