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

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.

Tactile perception of randomly rough surfaces

“…The quality of friction as predictor for decisions about similarity in Experiment 3 does not necessarily reveal the mechanisms underlying the similarity perception. Roughness and friction may be coupled as dimensions of tactile perception 44 . However, we suggest that the friction data report on the individual intensity of skin stimulation by roughness asperities in sliding touch for each trial and thus provide the a powerful metric to connect subjective similarity decisions with physical measurements.…”

“…The friction force and friction coefficient were calculated as where were the lateral force components and the normal force component. This definition of a linear coefficient is a standard in reporting tactile friction experiments 34 – 36 , 38 , 40 , 44 . Each of the 13 participants (6 male, age 22 to 53) explored 28 triplets typically in a total time of 45 minutes.…”

A Sticky Situation or Rough Going? Influencing Haptic Perception of Wood Coatings Through Frictional and Topographical Design

“…Although physical roughness and roughness perception have been investigated, it has been pointed out that there appears to be a lack of work assessing the relative contributions of different aspects of roughness [19]. In general, the focus is on single height parameters such as R a , which by no means uniquely define the surface topography.…”

“…In general, the focus is on single height parameters such as R a , which by no means uniquely define the surface topography. Although such parameters may be appropriate for general characterisation within more narrow contexts, a more exhaustive description is needed in order to describe the complexity of a surface in the context of haptic perception [19]. Additional factors such as feature shape and spacing are relevant since, via contact mechanical considerations, the morphology of the surface features affect the interaction between the surface and the finger, which in turn impacts the tactile experience [20,21].…”

A Curly Q: Is Frizz a Matter of Friction?

“…Despite a popular interest in how environmental factors influence perception of hair, surprisingly little research exists on the topic-much less any attempting to explain how interface properties such as tactile friction relate to how hair feels by touch. Tactile friction refers to the friction generated upon interaction between a surface and the fingertips and, in other applications, has been shown to influence tactile perception, for example, Skedung et al (2020). However, to our knowledge, to date no attempts have been made to find relationships between tactile friction and perception on hair.…”