Dynamic lumped element response of the human fingerpad

Area of Science:

• Biomechanics
• Human Factors Engineering
• Neuroscience

Background:

• The fingerpad's dynamic response is crucial for tactile sensation, precise object manipulation, and ergonomic design.
• Understanding in vivo fingerpad mechanics is essential for developing advanced human-computer interfaces and prosthetic devices.

Purpose of the Study:

• To investigate the dynamic lumped element response of the human fingerpad in vivo under compressive loading.
• To model the viscoelastic behavior of the fingerpad using a quasilinear approach.

Main Methods:

• In vivo indentation of the human fingerpad using a flat probe at constant velocity.
• Application of a compressive load ranging from 0 to 2 N.
• Development and validation of a quasilinear viscoelastic model against experimental data, including sinusoidal displacement tests.

Main Results:

• The fingerpad exhibited rapid force increase during indentation followed by force relaxation during the hold phase.
• The quasilinear viscoelastic model accurately described the experimental force-indentation and relaxation data.
• The model revealed an exponential increase in instantaneous elastic response with indentation depth and a reduced relaxation function composed of three decaying exponentials (time constants ~4 ms, 70 ms, 1.4 s) and a constant term.

Conclusions:

• The human fingerpad demonstrates complex viscoelastic behavior that can be effectively modeled using a quasilinear approach.
• The identified viscoelastic parameters provide quantitative insights into fingerpad mechanics, valuable for tactile sensory research and ergonomic applications.