Complexity, rate, and scale in sliding friction dynamics between a finger and textured surface

Area of Science:

• Biomechanics
• Neuroscience
• Materials Science

Background:

• Tactile perception of surface texture relies on complex friction dynamics between the skin and surfaces.
• Previous research has focused on neural mechanisms but lacked a full understanding of the physics of friction during touch.

Purpose of the Study:

• To investigate the nonlinear dynamics of sliding friction between human fingertips and textured surfaces.
• To compare experimental measurements with predictions from a biophysical model of the human finger.

Main Methods:

• Human fingertips slid against textured surfaces, with forces measured.
• A numerical model of a finger, incorporating realistic properties like geometry and hyperelasticity, was developed.
• Measured and simulated forces were analyzed using linear and nonlinear methods, including recurrence analysis.

Main Results:

• Both modeled and measured forces showed complex, nonlinear sliding friction dynamics and force fluctuations.
• The model accurately predicted force patterns, especially for faster sliding speeds and larger surface texture scales (>1mm).
• Discrepancies at slower speeds or finer textures were linked to complex interactions with skin features like fingerprints.

Conclusions:

• The study successfully modeled the complex frictional forces experienced during tactile exploration.
• Understanding these dynamics is crucial for deciphering how the brain perceives surface texture.
• The findings highlight the challenges in tactile texture perception due to intricate skin-surface interactions.