The contributions of skin structural properties to the friction of human finger-pads

Abstract

This paper describes three series of tests that were designed to investigate how skin mechanical and structural properties, measured using a "Cutometer" and Optical Coherence Tomography, affect the frictional behaviour of human finger-pads. Firstly, the skin mechanical properties across all fingers and the palm in participants' dominant hands were assessed. Results showed that the distensibility of skin (total deformation in a suction test) is associated with stratum corneum thickness and that this in turn affects friction (thicker stratuem corneum leads to higher friction), giving a link between distensibility and friction.Tape stripping to remove the superficial layer of the skin led to increased moisture (and/or electric charge on the skin surface) led to higher friction. No accompanying changes were seen in structural properties so it was concluded that moisture was the main cause of the adhesion increase. More work is required to isolate moisture and possible changes in electric charge using alternative measurement techniques.When rubbing with sand paper, the stratum corneum thinned considerably and friction reduced. Moisture was ruled out as a cause of friction changes in this instance. Skin normal stiffness also did not change, but lateral stiffness changes have been seen in previous work when the stratum corneum thickness has been reduced so this is likely to be the cause of the reduced friction. This will be investigated further in future work using dynamic OCT measurements.

Measuring contact area in a sliding human finger‐pad contact

“…The set-up is similar to that described in previous studies. [29][30][31] 2D cross-section OCT images are generally used to study the sub-surface structure of the skin.…”

“…Optical coherence tomography (OCT) has been used recently to investigate more closely the changes in ridge contact. [28][29][30] While only used so far for static measurements, this does has the possibility of being used for dynamic measurements which is a key next step in the development of tribological models of the finger-pad. More details of the data from the methods mentioned will be given in discussing the outcomes of the present work.…”

Influence of medical gloves on fingerpad friction and feel

“…Friction was measured using a similar experimental set-up to Derler & Rotaru (2013) and the same apparatus, as described in a previous study by Liu et al (2015). An index finger was first placed upon a test surface, mounted on a multi-component force plate (HE6X6, AMTI, dimensions 150 mm × 150 mm), capable of measuring applied forces in three orthogonal axes.…”

Influence of physico-chemical, mechanical and morphological fingerpad properties on the frictional distinction of sticky/slippery surfaces

“…The coefficients of determination R 2 range from 0.14 to 0.22 (t-test, p , 0.05), with a slightly higher correlation for the simulated surfaces. This correlation has been pointed out by Liu [49] with the help of spherical-shaped artificial fingers. His study shows the stiffer the material is, the lower the COF.…”