Effects of surface textures and shapes on perceived softness of hard materials

Abstract

This study investigated the influence of multiple surface features on the perceived surface softness during rubbing motion. Participants rubbed and ranked 13 types of 3D-printed rigid specimens with different macroscopic shapes and microscopic grains. A regression analysis revealed that the amplitude of the surface sinusoidal shape and the diameter of microscopic grains positively and negatively affected the signal-to-noise ratio calculated by the softness ranks, respectively. Smooth surfaces featuring a sinusoidal macroscopic shape with an amplitude of 0.5 mm felt softer than flat, smooth surfaces. By contrast, surfaces featuring grains with a diameter of 1 mm felt harder than the flat, smooth surfaces. These findings can help design soft-feeling product surfaces.