Evaluation of Young's modulus of skin tissue by indentation test based on modified Hertz contact theory

Abstract

An advantage of the indentation test is that it can be used to easily measure the elastic modulus of biological soft tissue in noninvasive. To measure Young's modulus, E*, of skin tissue by an indentation test, we expanded the Hertz contact theory to a contact problem of pressurizing an elastic plate of a finite thickness with an spherical indenter and devised a method to properly evaluate the modulus of skin tissue. To verify the validity of the indentation test method, we performed a tensile test and indentation test using artificial skin, and then, the optimum indent depth, δT0, was calculated at which the stiffness of both became equivalent. The modulus for the depth, δT0, was estimated for finite thickness plate from the modified Hertz contact equation, FTn = CδmT. Furthermore, we measured the strain distribution of subcutaneous tissue from ultrasonic echo tomography of human skin and found the effective depth, <z>, relating to stress transfer. Thus, we considered the practical applicability of a method for measuring the Young's modulus of skin tissue using an indentation tester.

Keywords

• indentation test
• pressure ulcer
• skin tissue
• hertz contact
• young&apos;s modulus
• sinking depth