Gecko toe and lamellar shear adhesion on macroscopic, engineered rough surfaces

Area of Science:

• Biomechanics
• Adhesion Science
• Materials Science

Background:

• The hierarchical adhesive system of geckos, involving setae, toes, and lamellae, is not fully understood.
• The specific role of intermediate-sized structures like lamellae in gecko adhesion on varied topographies is unclear.
• Understanding gecko foot morphology in relation to environmental topology is key to broader adhesion principles.

Purpose of the Study:

• To investigate the mechanical role of gecko toes and lamellae in adhesion on macroscopically rough surfaces.
• To quantify the effect of surface topography dimensions on gecko shear adhesion.
• To determine how gecko foot structures interact with environmental features to generate adhesion.

Main Methods:

• Utilized live Tokay geckos (Gekko gecko) to measure maximum shear force.
• Employed engineered substrates with controlled sinusoidal patterns (0.5 to 6 mm amplitudes and wavelengths).
• Analyzed adhesion based on the ratio of gecko lamella dimensions to substrate feature dimensions.

Main Results:

• Shear adhesion significantly decreased (up to 95%) on surfaces with feature sizes matching lamella dimensions.
• Gecko toes maintained substantial adhesion (60% shear force) on larger surfaces (3 mm amplitude) without claw engagement.
• Gecko adhesion performance is predictable based on the ratio of lamella size to surface feature size.

Conclusions:

• Macroscopic features of gecko toes and lamellae, including compliance and conformation, are vital for adhesion on rough surfaces, beyond just setae.
• The interaction between lamella dimensions and surface topography is a critical factor in gecko adhesion.
• These findings offer insights for designing advanced synthetic adhesives inspired by gecko biology.