Optimizing a Viscoelastic Finite Element Model to Represent the Dry, Natural, and Moist Human Finger Pressing on Glass

When a fingerpad presses into hard surface, the development of contact area depends on pressing force and speed. Importantly, it also varies with finger's moisture, presumably because hydration changes tissue's material properties. Therefore, we collected data from one finger repeatedly glass plate under three moisture conditions, constructed finite element model that optimized to simulate same scenarios. We controlled subject's be dry, natural, or moist recorded 15 trials in each condition. The measurements include normal over time plus finger-contact images are processed yield gross area. defined axially symmetric 3D model's lumped parameters an SLS-Kelvin (spring series parallel spring damper) for bulk tissue, elastic epidermal layer. Particle swarm optimization was used find parameter values cause simulation best match results show softness tissue reduces as becomes more hydrated. epidermis is softest, while natural has highest viscosity.