The finishing touches: the role of friction and roughness in haptic perception of surface coatings

Lisa Skedung,Kathryn L Harris,Elizabeth S Collier,Mark W Rutland

doi:10.1007/s00221-020-05831-w

Lisa Skedung, Kathryn L Harris + Show 2 more

Open Access

https://doi.org/10.1007/s00221-020-05831-w

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Abstract

Humans are extraordinarily skilled in the tactile evaluation of, and differentiation between, surfaces. The chemical and mechanical properties of these surfaces are translated into tactile signals during haptic exploration by mechanoreceptors in our skin, which are specialized to respond to different types of temporal and mechanical stimulation. Describing the effects of measurable physical characteristics on the human response to tactile exploration of surfaces is of great interest to manufacturers of household materials so that the haptic experience can be considered during design, product development and quality control. In this study, methods from psychophysics and materials science are combined to advance current understanding of which physical properties affect tactile perception of a range of furniture surfaces, i.e., foils and coatings, thus creating a tactile map of the furniture product landscape. Participants’ responses in a similarity scaling task were analyzed using INDSCAL from which three haptic dimensions were identified. Results show that specific roughness parameters, tactile friction and vibrational information, as characterized by a stylus profilometer, a Forceboard, and a biomimetic synthetic finger, are important for tactile differentiation and preferences of these surface treatments. The obtained dimensions are described as distinct combinations of the surface properties characterized, rather than as ‘roughness’ or ‘friction’ independently. Preferences by touch were related to the roughness, friction and thermal properties of the surfaces. The results both complement and advance current understanding of how roughness and friction relate to tactile perception of surfaces.

Highlights

Capable of differentiating between surfaces with topographical differences of only nanometers, humans are exquisitely sensitive to tactile information (Skedung et al 2013)
Humans have evolved to experience many different mechanical and temporal aspects of touch, and are able to describe haptic perception of surfaces in complex ways, often using the concept of dimensional space as a metaphor for differences between these sensations (for a review of how many and which tactile dimensions may be most relevant for human touch, see Okamoto et al (2013)
We tentatively suggest that dimension 1 here is illustrative of the difficulty participants sometimes have separating friction and roughness, given their strong dependence on one another, and it is possible that this dimension is representative of the lateral deformations in the finger caused by the roughness–friction relationship

Summary

Introduction

Capable of differentiating between surfaces with topographical differences of only nanometers, humans are exquisitely sensitive to tactile information (Skedung et al 2013). Often caused by contact with a solid surface, humans are sensitive to a cool breeze on a summer day, kinesthetic cues arising from movement. Humans have evolved to experience many different mechanical and temporal aspects of touch, and are able to describe haptic perception of surfaces in complex ways, often using the concept of dimensional space as a metaphor for differences between these sensations (for a review of how many and which tactile dimensions may be most relevant for human touch, see Okamoto et al (2013). Unlike mathematical descriptions of space, haptic dimensions

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