Microstructurally-based constitutive modelling of the skin - Linking intrinsic ageing to microstructural parameters

Area of Science:

• Biomechanics
• Materials Science
• Dermatology

Background:

• Intrinsic skin aging leads to changes in mechanical properties.
• Collagen and elastin fiber networks are crucial for skin's structural integrity.
• Understanding age-related microstructural alterations is key to predicting tissue behavior.

Purpose of the Study:

• To develop a multiphasic constitutive model of skin that incorporates intrinsic aging.
• To investigate the link between microstructural changes in collagen and elastin and skin's mechanical properties.
• To quantify the impact of aging on skin's stress-strain behavior.

Main Methods:

• A structurally-motivated constitutive model was formulated, separating contributions from collagen and elastin.
• Constitutive parameters were identified using published experimental data from human skin bulge tests.
• Numerical simulations were performed to analyze the effects of varying microstructural characteristics.

Main Results:

• Degradation of the elastin network and altered collagen anisotropy were identified as plausible mechanisms for age-related stiffening.
• Changes in elastin primarily affect the low-modulus region of the skin's stress-strain curve.
• Alterations in collagen significantly impact the linear region of the stress-strain curve.

Conclusions:

• The proposed constitutive model effectively captures age-related changes in skin mechanics.
• Microstructural remodeling of collagen and elastin networks are critical factors in skin aging.
• The model provides insights into the differential contributions of elastin and collagen to age-induced stiffening.