Feeling fine - the effect of topography and friction on perceived roughness and slipperiness

Abstract

(1) Background. To design materials with specific haptic qualities, it is important to understand both the contribution of physical attributes from the materials surfaces and the perceptions that are involved in the haptic interaction. (2) Methods. A series of 16 wrinkled surfaces consisting of two similar materials, of different elastic modulus and 8 different wrinkle wavelengths were thus characterized in terms of surface roughness and tactile friction coefficient. Sixteen participants scaled the perceived Roughness and Slipperiness of the surfaces using free magnitude estimation. Friction experiments were performed both by participants and by a trained experimenter with higher control. (3) Results and discussion. The trends in friction properties were similar for the group of participants performing the friction measurements in an uncontrolled way and the experiments performed under well-defined conditions, showing that the latter type of measurements represent the general friction properties well. The results point to slipperiness as the key perception dimension for textures below 100µm and roughness above 100µm. Furthermore, it is apparent that roughness and slipperiness perception of these types of structures are not independent. The friction is related to contact area between finger and material. Somewhat surprising was that the material with the higher elastic modulus was perceived as more slippery. A concluding finding was that the flat (high friction) references surfaces were scaled as rough, supporting the theory that perceived roughness itself is a multidimensional construct with both surface roughness and friction components.

Mechanisms of tactile sensory deterioration amongst the elderly

“…The nominal wavelengths of the test surfaces used in this same-different tactile perception test were 20 µm, 40 µm, 60 µm, 80 µm (denoted S20, S40, S60 and S80, respectively), 100 µm (Ref100) as well as a blank, smooth surface with no systematic texture (S0). Ref 100 is closest to the limit of what can be considered “fine texture” 19 . A pilot study with 10 elderly and 10 young female subjects indicated that the young group hit a threshold at 60 µm i.e ., that the difficulty of the task increased significantly for this wavelength and that S60 could not reliably be distinguished from Ref100.…”

“…It is known that roughness-smoothness, hardness-softness and stickiness-slipperiness are predominant perceptual (as opposed to physical) dimensions in macro texture perception 14 , 16 – 18 . This perceptual dimensionality remains intact when the texture scale is reduced to the micro- and nanoscale 19 . It is not clear whether the tactile discrimination ability for these textures remains intact with age.…”

“…While less studied, there is increasing evidence of the importance of the harder stratum corneum layer for friction 25 . Friction forces depend on the real area of contact, and thus the local deformability of the stratum corneum properties impacts this parameter 19 , 26 . Lévêque et al .…”

“…An earlier technical protocol using wrinkled surfaces 10 , 19 has thus been adapted to study in detail the changes in tactile perception ability that occur at advanced age using active touch on fine textures. The abilities of young and elderly participants to haptically discriminate between different, well defined patterned textures have been quantified, and compared to physical properties of the skin (finger friction, finger hydration and elasticity).…”

Feeling Smooth: Psychotribological Probing of Molecular Composition

“…Gueorguiev et al have studied glass and polymer samples to study the effect of varying surface chemistry on perception. In this case, both the topography and the elastic modulus are varied simultaneously with the surface chemistry, and both these parameters can be used as perceptual discriminators [1,20]. Nonetheless, the authors were able to successfully couple related perceptual discrimination to differences in an arbitrary spatial frequency parameter extracted from the tangential force.…”