A nonlinear elastic behavior to identify the mechanical parameters of human skin in vivo.
OBJECTIVE
Various analyses have been performed to identify the mechanical properties of the human skin tissue in vivo. They generally use different approaches and hypotheses (behavior laws as well as mechanical tests) and the obtained results are consequently difficult to analyze and compare. In this paper, an inverse method that can be adapted to any kind of mechanical tests and behavior laws is presented.


METHODS
A suction deformation performed on the volar aspect of the forearm of a subject is considered. This test is modeled with the finite element method to compare the experimental and simulated curves using an inverse method that allows the skin mechanical parameters identification. This process is based on two optimization algorithms, Kalman's filter and Gauss-Newton's methods. To account for the nonlinear behavior of the skin, a specific nonlinear elastic law, which is then compared with standard linear elastic and neo-Hookean's mechanical behaviors, was developed.


RESULTS
The obtained results first prove that neither linear elasticity nor neo-Hookean's laws can be used to model the skin. On the contrary, the nonlinear elastic model presents a relevant fit of the experimental curves. The skin thickness is also proved to be another key point to be taken into consideration.


CONCLUSIONS
The obtained results are successfully compared with literature and the reliability of the proposed method is underlined with the identification of 300 additional experimental curves. The different works we are currently focusing on are finally introduced.
Delalleau
A
A
Laboratoire de Tribologie et Dynamique des Systèmes, UMR 5513, CNRS, ECL, ENISE, Saint Etienne, France.
Josse
G
G
Lagarde
J-M
JM
Zahouani
H
H
Bergheau
J-M
JM
D000465:Algorithms; D003198:Computer Simulation; D004548:Elasticity; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D017711:Nonlinear Dynamics; D010808:Physical Examination / Q000379:methods*; D010812:Physical Stimulation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012879:Skin Physiological Phenomena; D012882:Skin Tests / Q000379:methods*; D013314:Stress, Mechanical; D014618:Vacuum