AuthorKuecken, Michael U.
AdvisorNewell, Alan C.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe fingerprint pattern (epidermal ridge pattern) becomes established at about the 10th to 16th week of pregnancy, when the lowest layer of the epidermis, the basal layer, becomes undulated. The pattern established by these undulations becomes visible on the skin surface in subsequent weeks of pregnancy. We argue that the undulation process is initiated by buckling of the basal layer. The necessary compressive stress is generated by differential growth. The instability is investigated using the classic von Karman equations for curved surfaces. The analysis reveals that ridges (rolls) are the most common pattern type and that the local ridge direction of the pattern is perpendicular to the direction of largest stress. For certain parameter regimes dot patterns (hexagons) are a stable solution of the equations. Such dot patterns are, in fact, observed on the palms of certain marsupials. The stress in the basal layer is induced by two mechanisms. First, the basal layer expands faster than the other skin structures. Such expansion is resisted at the major flexion creases and the nail furrow. Second, there is a change in fingertip geometry at the time of pattern generation that provides a different source of growth stress. The combination of the two processes predicts the correct sequence of pattern spread over the fingertip. It also explains the observation that fingerprint configurations are related to the fingertip geometry at the time of ridge formation. Computer simulations for the most important configurations exhibit many features of actual fingerprints and suggest directions for future work.
Degree ProgramGraduate College