Introduction of a New In-Situ Measurement System for the Study of Touch-Feel Relevant Surface Properties

Abstract

The touch-feel sensation of product surfaces arouses growing interest in various industry branches. To entangle the underlying physical and material parameters responsible for a specific touch-feel sensation, a new measurement system has been developed. This system aims to record the prime physical interaction parameters at a time, which is considered a necessary prerequisite for a successful physical description of the haptic sensation. The measurement setup enables one to measure the dynamic coefficient of friction, the macroscopic contact area of smooth and rough surfaces, the angle enclosed between the human finger and the soft-touch surfaces and the vibrations induced in the human finger during relative motion at a time. To validate the measurement stand, a test series has been conducted on two soft-touch surfaces of different roughness. While the individual results agree well with the literature, their combination revealed new insights. Finally, the investigation of the haptics of polymer coatings with the presented measuring system should facilitate the design of surfaces with tailor-made touch-feel properties.

Skin-skin contact: The normal-force dependence of the coefficient of friction between a bare finger and artificial skin changes randomly

“…It was observed that the exponential component of the normal force β, which was obtained from (4), was not constant and varied randomly, despite the same finger rubbing the same artificial skin surface under identical lubrication conditions. Previous studies have shown that β depends on various factors such as the material, lubrication conditions, and surface roughness [1,[8][9][10][11][12]15]. However, the dependence of the cof on the normal force is random, despite maintaining identical tribological conditions.…”

“…1. Various studies investigating the frictional forces acting on human skin focus on their dependence on the normal force, i.e., the exponent β in (4) [1,[8][9][10][11][12][13][14]. Because adhesion friction is a dominant force acting on dry human skin [4,[15][16][17], the real contact area responsible for the adhesion friction and its dependence on the normal force are two important factors as well [18].…”

“…Ules et al studied the variation of the frictional force when a finger slid over a glass surface with varying roughness values. The value of β was approximately 0 for a rough surface and approximately −0.5 for a smooth surface [11]. Han et al measured the maximum coefficient of static friction between an acrylic plate and a finger while varying the angle of contact of the finger.…”

“…We studied the dependence of the cof on the normal force by applying (4), which has been used in previous studies to calculate the friction between the skin and rigid bodies. Another model adopted in previous studies [11,21] provides a relationship between the cof and contact pressure. The cof model used in this study (4) does not utilize the contact pressure parameter because the true contact area could not be measured in our experimental setup.…”

The Relationship between a Defined Microstructure within the Mold Surface and the Corresponding Roughness on the Part: A Systematic Study on Particle Size, Filler-, and Compatibilizer Content

“…To summarize, the perception of a surface and its haptic properties are significantly influenced by roughness and microstructure, respectively, whereby non-negligible parameters include friction, contact area, temperature, and humidity between the human finger and the examined surface [ 24 ]. In particular, for a scientific investigation on haptic influences, the production of samples with a defined surface structure is indispensable.…”