Tactile samples with variable surface textures to investigate tactile perception characteristic

The ability to characterize tactile perception will be crucial to the effective use of tactile information in the next generation of information communication technology. Tactile perception depends on multiple properties of the surface being touched, including surface texture, stiffness, and temperature. To quantitatively evaluate the contribution of each individual property to tactile perception, our research group has used microfabricated tactile samples that have identical properties except for the one property under study. Until now, a separate sample has been needed for each level of each property of interest since the samples have lacked the capacity to vary property levels. In this research, we propose tactile samples that can change surface texture simply by being stretched. The proposed samples are made of PDMS and have grooves perpendicular to their length. In the initial state, the grooves are barely perceptible; however, when the sample is stretched lengthwise, the grooves open and surface texture appears. We first examined changes in the surface texture of the samples, together with Young's modulus, the friction coefficient, and the mean deviation of the friction coefficient (MMD), under controlled conditions. We then conducted sensory experiments involving friction, moisture, roughness, stiffness, and warmness. Experimental results showed that the surface texture could be well perceived with grooves greater than 30 μm in width. Contrary to our intuition, the friction feeling did not increase with the friction coefficient but rather with the MMD of the coefficient. The perception of moisture was enhanced with the friction coefficient. The proposed tactile samples, with their ability to change their surface texture, will be of great help in future quantitative investigations of tactile perception.