Measurement of the friction coefficient of the human skin in vivo - Quantification of the cutaneous smoothness

Introduction: Quality of smoothness of the skin is the combine result of its mechanical and frictional properties. Methods: A device was developed to characterize such a property in measuring the friction force between a reference material and the skin of the volar forearm. Results: The instrument showed a good reliability in using on steel roughness calibration plate, with the ability of the measuring unit to recognize different roughness from R-a = 0.4-50 mu m. Validation of the device was realized on dental silicone with the determination of a friction coefficient mu approximate to 0.42. Preliminaries tests in vivo on a 42 year-old woman showed a friction coefficient in the axis of the volar forearm of mu approximate to 0.7. In this study, each curve was the mean of ten tests for each load applied and for all curves the variation coefficient was found < 10%. Conclusion: This device provides an accurate quantitative measurement of the skin friction force. It can help us in further investigations to correlate each change with aging cosmetic product application, in relation to mechanical and microrelief properties. (C) 2000 Elsevier Science B.V. All rights reserved.