2.2.7. Contact angle measurements
The upper surface of the index finger was tested. A small amount of the investigated sample (approx. 0.05 g) was applied on the fingertip of the index finger and the sample was allowed to absorb for 3 min. To determine the contact angle between water and the investigated sample on the skin, a sessile drop of 3 μl of distilled water was applied to the skin area of interest using an automatic delivery device (DSA100 with software DSA3, Krüss, Germany), which was programmed to dose one drop of distilled water on the fingertip at beginning of each minute during 30 min. After the drop of water had touched the fingertip, a camera (high-resolution camera with a Falcon frame-grabber) took a picture of the water drop on the surface of the fingertip. The drop of water was absorbed by the tissue. The contact angle measurement of sessile drop on clean and degreased (ethanol 70%) skin of the fingertip was used as a control and gave high contact angle value