Relationship Between Spatial Variations in Static Skin Deformation and Perceived Roughness of Macroscopic Surfaces

The perceived roughness of macroscopic surface features is related to finger skin deformation. For example, skin indentation into surface grooves and the spatial variation in slowly adapting type 1 (SAI) mechanoreceptor activities are linked to the magnitude of subjective roughness. However, the perception of macroscopic roughness has not been directly linked to the spatial variations in skin deformation; therefore, this article investigated the relationship between the subjective roughness magnitude and the spatial spectrum of skin deformation through contact with roughened macroscopic surfaces. Experiments were performed to measure deformation of a finger pad when it statically touched different shaped grating scales. Then, the spatial spectra of skin deformation were computed by applying the Gabor filter with varying spatial selectivity. Some spectral components, particularly those for the spatial period ranging from 2.45-4.00 mm, exhibited a good correlation with the perceived roughness magnitude. When the optimal spatial periods were determined for individual subjects, the spectral components and perceived roughness exhibited a strong linear relationship with an average correlation coefficient of 0.94. Therefore, the amount of spatial variation in finger skin deformation can be linked to the subjective roughness intensities of macroscopic surface features.