Variables influencing the frictional behaviour of in vivo human skin

In the past decades, skin friction research has focused on determining which variables are important to affect the frictional behaviour of in vivo human skin. Until now, there is still limited knowledge on these variables. This study has used a large dataset to identify the effect of variables on the human skin, subject characteristics and environmental conditions on skin friction. The data are obtained on 50 subjects (34 male, 16 female). Friction measurements represent the friction between in vivo human skin and an aluminium sample, assessed on three anatomical locations. The coefficient of friction increased significantly (p<0.05) with increasing age, increasing ambient temperature and increasing relative air humidity. A significant inversely proportional relationship was found between friction and both the amount of hair present on the skin and the height of the subject. Other outcome variables in this study were the hydration of the skin and the skin temperatur

Skin friction: a novel approach to measuring in vivo human skin

The human skin plays an important role in people’s lives. It is in constant\ud interaction with the environment, clothing and consumer products.\ud This thesis discusses one of the parameters in the interaction between\ud the human skin in vivo and other materials: skin friction. The thesis is\ud divided into three parts. The first part is an introduction to skin friction\ud and to current knowledge on skin friction. The second part presents the\ud RevoltST, the tribometer that was specially developed for skin friction\ud research and which meets the objectives described in the thesis. The third\ud part presents the results of the skin friction measurements obtained with\ud the RevoltST

A multivariable model for predicting the frictional behaviour and hydration of the human skin

Background The frictional characteristics of skin-object interactions are important when handling objects, in the assessment of perception and comfort of products and materials and in the origins and prevention of skin injuries. In this study, based on statistical methods, a quantitative model is developed that describes the friction behaviour of human skin as a function of the subject characteristics, contact conditions, the properties of the counter material as well as environmental conditions. Aims Although the frictional behaviour of human skin is a multivariable problem, in literature the variables that are associated with skin friction have been studied using univariable methods. In this work, multivariable models for the static and dynamic coefficients of friction as well as for the hydration of the skin are presented. Materials & Methods A total of 634 skin-friction measurements were performed using a recently developed tribometer. Using a statistical analysis, previously defined potential influential variables were linked to the static and dynamic coefficient of friction and to the hydration of the skin, resulting in three predictive quantitative models that descibe the friction behaviour and the hydration of human skin respectively. Results and Discussion Increased dynamic coefficients of friction were obtained from older subjects, on the index finger, with materials with a higher surface energy at higher room temperatures, whereas lower dynamic coefficients of friction were obtained at lower skin temperatures, on the temple with rougher contact materials. The static coefficient of friction increased with higher skin hydration, increasing age, on the index finger, with materials with a higher surface energy and at higher ambient temperatures. The hydration of the skin was associated with the skin temperature, anatomical location, presence of hair on the skin and the relative air humidity. Conclusion Predictive models have been derived for the static and dynamic coefficient of friction using a multivariable approach. These two coefficients of friction show a strong correlation. Consequently the two multivariable models resemble, with the static coefficient of friction being on average 18% lower than the dynamic coefficient of friction. The multivariable models in this study can be used to describe the data set that was the basis for this study. Care should be taken when generalising these results

A novel approach to measuring the frictional behaviour of human skin in vivo

Friction involving human skin plays a key role in human life. The availability of a portable tribometer improves the accessibility to large number of both subjects and anatomical sites. This is the first mobile device suitable to measure skin friction with a controlled and variable normal load (range 0.5–2 N) and velocity (range 1–10 mm/s) of a material of choice making a sliding rotational movement over the skin. The results of a pilot study, using stainless steel samples on the ventral forearm compare to results in the literature. The new device can be used for more extensive research to found these results and determine the effects of normal load or sliding velocity on the skin's frictional behaviou