Age-dependent biomechanical properties of the skin (original) (raw)
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Medical Engineering & Physics, 2012
The assessment of human tissue properties by objective and quantitative devices is very important to improve the understanding of its mechanical behaviour. The aim of this paper is to present a non contact method to measure the mechanical properties of human skin in vivo. A complete non contact device using an air flow system has been developed. Validation and assessment of the method have been performed on inert visco-elastic material. An in vivo study on the forearm of two groups of healthy women aged of 23.2 ± 1.6 and 60.4 ± 2.4 has been performed. Main parameters assessed are presented and a first interpretation to evaluate the reduced Young's modulus is proposed. Significant differences between the main parameters of the curve are shown with ageing. As tests were performed with different loads, the influence of the stress is also observed. We found a reduced Young's modulus with an air flow force of 10 mN of 14.38 ± 3.61 kPa for the youngest group and 6.20 ± 1.45 kPa for the oldest group. These values agree with other studies using classical or dynamic indentation. Non contact test using the developed device gives convincing results.
On the stress-strain relation for skin
Journal of Biomechanics, 1979
A simple model of the collagen fiber network in the dermis is used to calculate the strain level at which the stiffness of skin abruptly increases. The calculated critical strain level (57%) agrees roughly with expetimental values. It is suggested that entry into the high-modulus region of the stress-strain curve of skin is simply a geometric e&t%, corresponding to thorough alignment, along the stress direction, of the fibers in the collagen network. The model finds use in systematizing data on the e&t of age on the long-range extensibility of skin and on the morphological basis of skin extensibihty along and across Langer's lines.
Effect of human ageing on skin rheology and tribology
Wear, 2011
Microscopic observations of the human skin have shown that skin topography contains a network of lines whose organization reflects the multidirectional tensions of elastic and collagen fibres in the superficial dermis. This morphology is present at birth and its scale of depth and wavelength increases with age until puberty.The aim of this work is to study how human ageing influences skin morphology, elasticity, loss factor, damping and skin tribology. A complete device to assess the rheology of the skin has been developed. The frequency and strain amplitude range from 10 to 60 Hz and from 1 to 10 μm. An in vivo study including dynamic indentation and tribologic analysis has been performed on 46 subjects aged from 18 to 70 falling into 3 groups.The complex modulus measured by dynamic indentation at 10 Hz frequency stress ranges from 7.17 ± 2.06 kPa for the oldest group to 10.7 ± 2.64 kPa for the youngest group. The combination of the dynamic device with acoustic measurements during friction gives an invaluable help to understand the significance of energy dissipation during friction and shows the impact of skin rheology on acoustic signature during ageing.
[Utility of Skin Elasticity Index as an Aging Index]
- Takema Y, Imokawa G: The effects of UVA and UVB irradiation on the viscoelastic properties of hairless mouse skin in vivo. Dermatology 1998 196 397-400 2) Nishimori Y, Edwards C, et al.: Degenerative alteration of dermal collagen fiber bundles in photodamaged human skin and UV-irradiated heirless mouse skin: possible effect on
Evaluation of Aging Effects on Skin Wrinkle by Finite Element Method
Journal of Biomechanical Science and Engineering, 2008
The reason why the wrinkle suddenly becomes prominent at a middle age is addressed from biomechanical standpoint. The multistage buckling theory we have derived concludes that the sudden enlargement of wrinkle comes from a switch of the specific buckling mode from the horny buckling to the epidermal buckling. In this study, the validity of this conclusion was reexamined by the finite element buckling analysis of the human facial skin with a linear aging model. Comparison of results between the beam model and the finite element model unraveled the mechanism of the buckling mode switch. By simulating the three cases: epidermal aging, dermal aging, and full aging, we found that the mode switch mainly comes from the epidermal aging, that is, the stiffening and thinning of the epidermis. The dermal aging was not a trigger of the mode switch in the linear buckling of linear aging skin model.
Dynamic Tensile Properties of Human Skin
The mechanical properties of skin are important for a number of applications including surgery, dermatology, impact biomechanics and forensic science. Studies have shown that the anisotropic effects of skin have been linked to sample orientation with respect to contour lines of tension, i.e. the Langer's lines. There have been numerous studies undertaken to calculate the influence of Langer's lines on the mechanical properties of human skin at quasistatic strain rates; however, it is relatively unknown what occurs at dynamic speeds. This study conducts a number of dynamic mechanical tensile tests to investigate the influence dynamic speeds have on the mechanical properties of human skin. The testing protocol involves uniaxial tensile tests at three different dynamic speeds, 1m/s, 1.5m/s and 2m/s, performed using an Instron tensile test machine. A total of 33 tests were conducted on 3 human cadavers aged 85, 77 and 82. Samples were excised at specific locations and orientations with respect to the Langer's lines. The purpose for this was to recognise the significance that location and orientation have on the mechanical properties of human skin. The mean ultimate tensile strength (UTS) was 27.2±9.3MPa, the mean strain energy was 4.9±1.5MJ/m 3 , the mean elastic modulus was 98.97±97MPa and the mean failure strain was 25.45±5.07%. This new material data for human skin can be applied to constitutive models in areas such as impact biomechanics, forensic science and computer-assisted surgery.
Mechanisms of ageing and development, 2017
Skin aging is associated with alterations of surface texture, sebum composition and immune response. Mechanical stress induces repair mechanisms, which may be dependent on the age and quality of the skin. The response to mechanical stress in young and aged individuals, their subjective opinion and objective effectiveness of skin care products were evaluated by biophysical skin quality parameters (stratum corneum hydration, transepidermal water loss, skin pH, pigmentation and erythema) at baseline, 1, 6, 24hours and 7days at the forearms of 2 groups of healthy volunteers, younger than 35 years (n=11) and older than 60 years (n=13). In addition, casual surface lipid composition was studied under the same conditions at the baseline and day 7 after mechanical stress induction. Evaluations were also performed in stressed skin areas treated daily with skin care products and the subjective opinion of the volunteers was documented. The tested groups exhibited age-associated baseline skin fu...