Their surfaces have to be impregnated by silicide acid or synthetic materials. Sands polluted by oil can be cleaned by treatment with surfactant solutions. The progress of the cleaning process can easily be controlled by contact angle measurements on the treated and pretreated samples. The tightness of rubber sealing caps on glass surfaces can be predicated by surface free energy measurements. Artificial bones and artificial organs have to have a certain surface free energy to be accepted by the human body.
Tubes transporting body fluids have to avoid the buildup of agglomerates.
The same is the prerequisite for biomembranes. The wettability of contact lenses as well as the interaction and the effectiveness of cleaning solution formulation for contact lenses can be examined by contact angle measurement. The contact angle of saliva on tooth surfaces depends on the materials used in the cleaning process. Artificial material must have a certain surface tension and polarity in order to avoid deposition of bacteria and in case of transplants to ensure good adhesion between tooth and embodiment. According to its use the paper has to be strongly or weakly hydrophobic or hydrophilic.