Surface deflection of primate fingertip under line load

Area of Science:

• Biomechanics
• Neuroscience
• Dermatology

Background:

• Understanding the biomechanics of skin and soft tissues is crucial for elucidating the mechanisms of touch sensation.
• Mechanoreceptive nerve terminals in the skin are responsible for tactile perception.

Purpose of the Study:

• To investigate the mechanical properties of the fingertip in vivo.
• To compare the predictive accuracy of different biomechanical models for skin deformation.
• To propose an improved model for fingertip mechanics.

Main Methods:

• In vivo indentation of human and monkey fingertips using a sharp wedge line load.
• Photographic recording of the resulting skin surface deflection profiles.
• Comparison of empirical data with predictions from an elastic half-space model and a proposed fluid-filled membrane model.

Main Results:

• The elastic half-space model (modified Boussinesq solution) provided only a rough approximation of observed skin deflection profiles.
• The proposed fluid-filled membrane model, considering finite deformations, demonstrated excellent agreement with empirical deflection profiles.
• The improved model accurately predicted profiles within approximately 3 mm of the applied load.

Conclusions:

• The fingertip's mechanical behavior is better represented by a fluid-filled membrane model than a simple elastic half-space model.
• This finding has implications for understanding tactile sensation and developing more accurate models of skin biomechanics.
• The study highlights the importance of considering finite deformations and internal fluid dynamics in fingertip mechanics.