Abstract
Computational analysis of free and forced vibration responses provides crucial information on the dynamic characteristics of deformable bodies. Although such numerical techniques are prevalently used in many disciplines, they have been underutilized in the quest to understand the form and function of human fingers. We addressed this opportunity by building DigiTip, a detailed three-dimensional finite element model of a representative human fingertip that is based on prior anatomical and biomechanical studies. Using the developed model, we first performed modal analyses to determine the free vibration modes with associated frequencies up to about 250 Hz, the frequency at which humans are most sensitive to vibratory stimuli on the fingertip. The modal analysis results reveal that this typical human fingertip exhibits seven characteristic vibration patterns in the considered frequency range. Subsequently, we applied distributed harmonic forces at the fingerprint centroid in three principal directions to predict forced vibration responses through frequency-response analyses; these simulations demonstrate that certain vibration modes are excited significantly more efficiently than the others under the investigated conditions. The results illuminate the dynamic behavior of the human fingertip in haptic interactions involving oscillating stimuli, such as textures and vibratory alerts, and they show how the modal information can predict the forced vibration responses of the soft tissue.
Highlights
We developed DigiTip, a detailed 3D finite element model of the human fingertip based carefully on prior studies of fingertip anatomy and biomechanics
This study focuses on the dynamic analysis of a human fingertip through computational simulations
We utilized frequency-response analyses to predict forced vibration responses of the fingertip excited by harmonic forces applied on a small patch of skin at the fingerprint centroid in three orthogonal directions
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Wu et al [10] performed two-dimensional (2D) finite element (FE) analyses to simulate the mechanical response of the human fingertip periodically pressing onto flat surfaces Their results endorsed the suitability of FE simulations in analyzing finger deformation mechanics since their predictions on contact force histories and fingertip–surface separation periods agreed well with the reported experimental observations. The deformation of continuum bodies under dynamic loads is directly influenced by the object’s natural frequencies and mode shapes These modal features have remained unexplored for the fingertip, despite the high interest in the dynamic analysis of human tissue. The results offer insights into the probable dynamic behavior of the fingertip in haptic applications involving artificial vibratory feedback or light sliding contact with undulating surfaces They demonstrate the convenience of utilizing modal information to predict the forced vibration responses of the skin
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