Analysis of skin deformation profiles during sinusoidal vibration of fingerpad

Vibrotactile perception threshold measurement has been widely used to diagnose the severity of peripheral neuropathy associated with hand-arm vibration syndrome and sensory losses in stroke and diabetic patients. The vibration perception threshold is believed to be influenced by many factors, such as contact force and vibration frequency. The present study is intended to analyze, theoretically, the time-dependent deformation profile of skin surface, strain distributions within soft tissue, and response force of a fingertip when it is stimulated by a probe vibrating with a sinusoidal movement. A two-dimensional finite element model, which incorporates the essential anatomical structures of a finger: skin, subcutaneous tissue, bone, and nail, has been proposed to analyze the effects of vibration amplitude, frequency, and preindentation on the dynamic interaction between the fingerpad and vibrating probe. The simulation results suggest that the fraction of time over which the skin separates from the probe during vibration increases with increasing vibration frequency and amplitude, and decreases with increased preindentation of the probe. The preindentation of the probe has been found to significantly reduce the trend of skin/probe decoupling. The simulation results show reasonably consistent trends with the reported experimental data.