Influence of the relative humidity and the temperature on the in-vivo friction behaviour of human skin

•The frictional behaviour of skin is a function of the humidity and the temperature.•The product of the humidity and temperature appears to be the driving force.•At 40% RH the coefficient of friction does not significantly vary with temperature.•Increased sensitivity of friction in a warm, moist conditions to change in T and RH•Microclimate management can contribute to reducing shear induced tissue injuries.

Both temperature and relative humidity are known to influence the frictional behaviour of human skin. However, literature does not completely cover to what extent both parameters play a role. Measurements were conducted using an in-house built reciprocating tribometer inside an enclosure in which both the humidity and the temperature can be controlled independently. Friction measurements were performed in varying climates ranging from 25 °C and 40% RH to 37 °C and 80% RH at respectively 3 °C and 10% RH intervals. Using the obtained results a ‘friction map’ was created which shows that the coefficient of friction increases by a factor of two when the environment is changed from ‘cold and dry’ to ‘warm and moist’. A statistical analysis shows that the product of the temperature and relative humidity appears to be the driving factor describing the observed frictional behaviour. Results indeed show a more pronounced effect of either parameter at the warmer, moister conditions, in contrast to the colder, drier conditions where a smaller effect on the coefficient of friction is observed. The findings will be of importance, e.g. for bedridden patients who are prone to pressure ulcer development as it indicates the importance of maintaining a healthy microclimate.