title: Compressive viscoelasticity of freshly excised mouse skin is dependent on specimen thickness, strain level and rate.
abstract: Although the skin's mechanical properties are well characterized in tension, little work has been done in compression. Here, the viscoelastic properties of a population of mouse skin specimens (139 samples from 36 mice, aged 5 to 34 weeks) were characterized upon varying specimen thickness, as well as strain level and rate. Over the population, we observed the skin's viscoelasticity to be quite variable, yet found systematic correlation of residual stress ratio with skin thickness and strain, and of relaxation time constants with strain rates. In particular, as specimen thickness ranged from 211 to 671 μm, we observed significant variation in both quasi-linear viscoelasticity (QLV) parameters, the relaxation time constant (τ1 = 0.19 ± 0.10 s) and steady-state residual stress ratio (G∞ = 0.28 ± 0.13). Moreover, when τ1 was decoupled and fixed, we observed that G∞ positively correlated with skin thickness. Second, as steady-state stretch was increased (λ∞ from 0.22 to 0.81), we observed significant variation in both QLV parameters (τ1 = 0.26 ± 0.14 s, G∞ = 0.47 ± 0.17), and when τ1 was fixed, G∞ positively correlated with stretch level. Third, as strain rate was increased from 0.06 to 22.88 s-1, the median time constant τ1 varied from 1.90 to 0.31 s, and thereby negatively correlated with strain rate. These findings indicate that the natural range of specimen thickness, as well as experimental controls of compression level and rate, significantly influence measurements of skin viscoelasticity.
authors: Department of Systems and Information Engineering, University of Virginia, 151 Engineers Way, Charlottesville, Virginia, 22903, United States of America; Department of Mechanical and Aerospace Engineering, University of Virginia, 122 Engineers Way, Charlottesville, Virginia, 22903, United States of America.
authors: Yuxiang
authors: Y
authors: Wang
authors: Department of Dermatology, Columbia University College of Physicians & Surgeons, 1150 St. Nicholas Ave., New York, New York, 10032, United States of America.
authors: Kara L
authors: KL
authors: Marshall
authors: Department of Dermatology, Columbia University College of Physicians & Surgeons, 1150 St. Nicholas Ave., New York, New York, 10032, United States of America.
authors: Yoshichika
authors: Y
authors: Baba
authors: Department of Dermatology, Columbia University College of Physicians & Surgeons, 1150 St. Nicholas Ave., New York, New York, 10032, United States of America; Department of Physiology & Cellular Biophysics, Columbia University College of Physicians & Surgeons, 1150 St. Nicholas Ave., New York, New York, 10032, United States of America.
authors: Ellen A
authors: EA
authors: Lumpkin
authors: Department of Systems and Information Engineering, University of Virginia, 151 Engineers Way, Charlottesville, Virginia, 22903, United States of America; Department of Biomedical Engineering, University of Virginia, 415 Lane Road, Charlottesville, Virginia, 22908, United States of America.
authors: Gregory J
authors: GJ
authors: Gerling
mesh_terms: D000818:Animals; D019245:Compressive Strength; D003198:Computer Simulation; D004548:Elasticity; D051379:Mice; D008954:Models, Biological; D012867:Skin / Q000737:chemistry*; D013314:Stress, Mechanical; D014783:Viscosity