Friction behavior between an artificial skin block and a glass plate under unlubricated and partly/completely water-lubricated conditions

It is usually difficult to separate plastic bag through a dry or dripping wet finger due to low friction. Although a moist finger, enabled by exposing the skin to small amount of water exhibits higher friction, the reason has not yet been scientifically justified. We showed that the real contact area and friction coefficient between an artificial skin block with fingerprint pattern and a glass plate reaches a maximum when about 5% of contact area is covered by water. In such a high friction condition, the real contacts are surrounded by a meniscus. Thus, the real contact formation is promoted by negative pressure at the meniscus. •Contact condition and friction of artificial skin on glass were examined.•Water and air were coexisted on interfaces for partly lubricated conditions.•Real contacts were surrounded by water droplets for partly lubricated conditions.•Real contact formation was promoted by adding a small amount of water.•Adding a small amount of water also induced increase in friction coefficients.