Effect of surface textures on the fingertip forces perception and output

Humans use their tactile sensation to perceive hardness and roughness of an object they touch. Hardness and roughness feeling are related to the contact area and the pressure distribution of the contact surface. Also it is known that the perceived force of a grasped object changes depending on the curvature of the contact surface. The surface texture will affect not only the hardness and roughness feeling but also force perception. In this study, we investigated the effect of a texture with different surface shape on the force perception and hardness feeling of an object. This paper conducted an experiment to reproduce the force felt when an acrylic plate with different surface textures was pressed, and the sensation of hardness and roughness felt during the experiment was evaluated by questionnaire. The texture has a pyramidal shape with aligned projections. In the experiments, we used three different textures with projections of 0.08, 0.2, and 0.5 mm in height, and applied reference forces of 1.1, 2.7, 3.3, 5.0, and 7.8 N. As a result of the experiment with 14 healthy young adults, a statistically significant difference in the exerted force was observed depending on the height of the texture when the reference force was 3.3 N. It was also found that the height had an effect on the roughness but not on the hardness.