In this paper, we study the influence of the fingerprint and sweat on the fingerprint on the friction between the hand and an object. When sweat contacts a finger or an object, it is sometimes easy to pick up the object. In particular, we can see this phenomenon when grasping a thin object such as paper and vinyl. The reason for this phenomenon is the increase of friction force, and this paper physically analyzes this natural phenomenon. To this end, we investigate the cause of the friction force between a solid and liquid to calculate the friction force when water is present within the fingerprint. To support the theoretical analysis, we conduct experiments to measure the friction force by making a finger-shaped silicon specimen. By comparing the theoretical and experimental results, we defined the change of friction force if there was water in the fingerprint. Through this study, it is possible to analyze the role of the fingerprint and sweat on the finger, and thereby explain the friction change depending on the amount of sweat.
