Comparative evaluation of suction-based apparent mechanical properties of skin and fat across aperture sizes and...

Many therapeutic and diagnostic devices apply suction pressure over relatively large surface areas, leading to substantial deformation of the skin and underlying adipose tissue. Most studies estimating hyperelastic properties under suction have focused on small apertures that primarily deform the skin. In this study, a participant-specific three-dimensional finite element model of the forearm was employed to estimate the apparent hyperelastic properties of skin and fat under suction pressures up to 203.2 mmHg and to evaluate whether properties identified at one aperture can predict deformation at 16 mm, 30 mm, and 50 mm apertures under identical loading conditions. Isotropic hyperelastic properties were identified by minimizing the difference between experimental and numerical displacements across multiple pressure levels. Using properties estimated from the 50 mm aperture condition to predict deformation at smaller apertures resulted in an average error of 12.6% for 30 mm and 45% for 16 mm, indicating that apparent hyperelastic properties identified under one suction geometry may not generalize across different aperture sizes due to variations in strain distribution and tissue recruitment, using this model. Fat thickness significantly affected deformation and stress predictions at the 50 mm aperture. A 2 mm reduction in fat thickness increased circumferential, axial, and shear stresses within the fat layer. These findings indicate that tissue deformation under suction depends on pressure level, aperture size, and tissue thickness. Therefore, both load scale and length scale must be considered in soft-tissue modeling for suction-based medical devices.