Viscoelastic Properties of Intact Human Skin: Instrumentation, Hydration Effects, and the Contribution of the Stratum Corneum

Abstract

Past attempts to relate mechanical properties of the stratum corneum to its state of hydration or disease condition have been hampered by the lack of adequate in vivo methodology. With the technique described herein, viscoelastic properties of the skin surface can be measured in vivo or on excised skin in vitro. This method is sensitive enough to detect changes in the properties of the stratum corneum induced by topically applied agents or by mechanical disruption of it. The viscoelastic data suggest that the outermost layers of the stratum corneum may become dry in vivo despite their proximity to the underlying wet tissue, and that the instrument is sensitive enough to measure the changes that occur. It also appears that the in vivo behavior of the stratum corneum is similar to that of isolated stratum corneum membranes which become brittle when they are dried and supple when they are hydrated.

Skin Bioengineering in the Noninvasive Assessment of Cutaneous Aging

“…Age-related changes in mechanical properties of the skin have been studied in vivo using different noninvasive techniques [1] and methods [2][3][4]. Tensile tests (uniaxial and biaxial) arc straightforward methods [5] and show a marked age dependency because the magnitude of the ini tial elastic deformation decreases with age according to the degenerative changes induced in the dermal elastic network [6] (fig.…”

“…Stress-strain relationship and changes induced by aging. A typical curve (dotted line) shows an initial deformation controlled by elastic fibers (1) followed by a second phase where collagen fibers are straightened (2) and bear the load (3). See text for details.…”

Indentation Versus Tensile Measurements of Young's Modulus for Soft Biological Tissues

“…However, the time dependent, viscous properties of biological tissues are important and we direct readers to the following reviews and articles, which discuss these properties for many of the tissues reviewed here. [54][55][56][57][58][59][60][61][62] In addition, values, such as the tangent modulus, obtained from regions of stress-strain curves that are outside of the elastic regime are not included in this review. Where possible, we compare YM values obtained when both values (by indentation and tensile stretching) for a given tissue have been reported (not all tissues we reviewed have reported values for both methods).…”

The importance of hydration in wound healing: reinvigorating the clinical perspective

“…36,37 A number of studies have suggested additional changes to the layers of the skin occur, particularly in the SC and include altered permeability and flexability, viscoelastic properties, weakened intercellular attachment and changes in electrical impedance properties. [38][39][40][41][42][43][44] The physical structure of the epidermis can be particularly affected. 45,46 However, other studies have suggested that hydration-induced changes to the epidermis are quickly reversed upon removal of the cause.…”