Static friction properties between human palmar skin and five grabrail materials

Area of Science:

• Biomechanics
• Tribology
• Human Factors Engineering

Background:

• Understanding friction between human skin and surfaces is crucial for designing safe interfaces.
• Grabrails are common in environments where hand conditions (dry, wet, soapy) can vary, impacting grip.
• Previous research has not comprehensively evaluated static friction across diverse grabrail materials and hand conditions.

Purpose of the Study:

• To investigate the static friction properties between human palmar skin and various grabrail materials.
• To assess the influence of hand conditions (dry, wet, soapy) on friction.
• To identify optimal grabrail materials for different hand conditions.

Main Methods:

• Thirty subjects (15 female, 15 male) participated.
• Static friction was measured using a three-dimensional force measurement system on five grabrail materials: chrome, stainless steel, powder-coated steel, textured aluminum, and knurled steel.
• Tests were conducted with dry, wet, and soapy hands; normal force, friction force, and coefficient of static friction were recorded.

Main Results:

• Gender, age, and hand size did not significantly influence friction results.
• Soapy hands resulted in significantly lower coefficients of friction and friction forces compared to dry or wet hands.
• A significantly greater normal force was applied with soapy hands.
• Textured materials showed superior friction with soapy hands; smooth materials performed best with dry hands.

Conclusions:

• Hand condition, particularly soapiness, is a critical factor affecting grabrail friction.
• Grabrail material selection should consider the expected hand conditions for optimal safety and grip.
• Textured surfaces are recommended for environments where hands may be soapy.