Study of Physiological Parameters and Comfort Sensations During Friction Contacts of the Human Skin

As a living tissue, human skin has a biological response when it rubs against other external surfaces, among which, the comfort sensation attributes during friction contact make an important contribution to one's quality of life. However, limited quantitative parameters can be used to describe the sensations, and they have rarely been studied scientifically. In this paper, the comfort sensations of human volar forearm skin during friction testing were studied by biofeedback of physiological and psychological responses. A UMT-II tribometer was used to measure tribological parameters of the skin under different normal force of 0.2 and 1.0 N, and corresponding comfort sensations of the skin were assessed quantitatively using BioTrace + for physiological signals monitoring: skin conductance, skin temperature, and electroencephalogram (EEG). The psychological responses were characterized qualitatively according to the volunteers' sensations of pain, drag, and heat. Results showed that the tangential force, amplitudes of EEG signals and psychological responses increased with the normal force increasing. The friction coefficients, differences of skin conductance and temperature, amplitudes of EEG signals, and psychological responses gradually decreased with the number of friction tests increasing. The discomfort sensations of human skin were strongly related to friction conditions, which intensified under the large normal force, and gradually weakened with the number of tests increasing. The physiological responses were in accord with the psychological ones. The comfort sensations during friction testing can be assessed quantitatively by the physiological signals of conductance, temperature, and EEG.