Numerical analysis of the strain distribution in skin domes formed upon the application of hypobaric pressure

TL;DR

This study compares linear elastic and hyperelastic models to predict skin deformation under hypobaric pressure, finding hyperelasticity more accurate for strain distribution, which is crucial for designing safe skin-contact devices.

Contribution

It demonstrates the limitations of linear elasticity in predicting skin strain and highlights the importance of hyperelastic models for accurate 3D strain analysis.

Findings

Linear elasticity overpredicts strain at the dome rim.

Hyperelasticity accurately predicts 3D strain distribution.

Skin thickness reduces under hypobaric pressure.

Abstract

Suction cups are widely used in applications such as in measurement of mechanical properties of skin in vivo, in drug delivery devices or in acupuncture treatment. Understanding the mechanical response of skin under hypobaric pressure are of great importance for users of suction cups. The aims of this work are to assess the capability of linear elasticity (Young's modulus) or hyperelasticity in predicting hypobaric pressure induced 3D stretching of the skin. Using experiments and computational Finite Element Method modelling, this work demonstrated that although it was possible to predict the suction dome apex height using both linear elasticity and hyperelasticity for the typical range of hypobaric pressure in medical applications (up to -10 psi), linear elasticity theory showed limitations when predicting the strain distribution across the suction dome. The reason is that the stretch ratio reaches values exceeding the initial linear elastic stage of the stress-strain characteristic curve for skin. As a result, the linear elasticity theory overpredicts the stretch along the rim of domes where there is stress concentration. In addition, the modelling showed that the skin was compressed consistently along the thickness direction, leading to reduced thickness. Using hyperelasticity modelling to predict the 3D strain distribution paves the way to accurately design safe commercial products that interface with skin.