Spatial Probing of the Properties of the Human Hair Surface Using Wilhelmy Force Profiles

The study investigated the surface properties of human hair, revealing that the hair surface is not homogeneous but exhibits systematic changes in wettability along its length. By analyzing hair segments from female participants, the researchers found daily and weekly patterns in wettability, linked to wake and sleep phases, and suggested monthly changes possibly related to the menstrual cycle. These findings indicated that the hair surface records detailed chronobiological information through a spatial distribution of hydrophobic and hydrophilic regions.