An in vivo study of the mechanical properties of facial skin and influence of aging using digital image speckle correlation

Abstract

The skin on the face is directly attached to the muscle through the superficial musculoaponeurotic system. We show that this can be used to probe skin mechanical properties, in vivo, using, digital image speckle correlation (DISC), a technique that measures the intrinsic cutaneous pore structure displacement following a natural facial deformation. We take a series of images, which are then analyzed with DISC to create a displacement vector diagram, from which we can obtain spatially resolved information regarding facial deformation. We then studied the functional form of the displacement as a function of age, location on the face, and skin treatment. Finally, through DISC vector field analysis we investigate the mechanism of wrinkle formation. We first show that facial skin displacement follows the direction of muscular movement and reflects the magnitude of the applied forces. Using DISC vector field analysis, we find that as the skin ages the distribution of forces becomes more condensed, with a marked spatial asymmetry. Analysis of the data, in the perioral region, we find that the skin elasticity decreases exponentially with age, with a decay constant of approximately 32 years. Similar results, but with a larger amplitude, were also found for the periorbital region. Finally, DISC vector field analysis also shows that the location of maximal stress correlated with the location of existing facial wrinkles. The DISC method, as a non-contact technique, is a potential clinical research tool for the diagnosis of facial skin condition and underlying muscular activity. We demonstrate how these factors can be used to monitor the effects of aging, formation of wrinkles, and the efficacy of topical applications of skin creams.