Tuesday, 8 March 2011

Skin Critical Surface Tension

I was thinking today how can skin get more wet? (Actually I just wanted to post a video of someone getting hit by a water balloon). I am not sure yet. However, I found some answers on this thing called the internet. Someone managed to solve it. A. El Khyat et. al (2006) mentioned that the skin critical surface tension (CST), an index of wettability. As you can see from the video below the skin surface is primarily hydrophobic (so not all the water is absorbed to it although the balloon is moving quite fast in slow motion) and paradoxically becomes more wettable through its lipidic component.

Forehead CST was above 50.7 dyne/cm and by defatting (getting rid of some of the fat) it reduces the skin surface tension. However, by replacing some of the fat (naturally or with cream) your skin becomes more wettable.

Note: The CST was calculated using the Zisman equation, from the contact angle at equilibrium, of droplets of liquids whose surface tension was known. Contact angles were computed from the base and the height of the droplets viewed from their side through an operating microscope provided with a slanted mirror. Both volar forearm and forehead were studied.