Importance of loading and unloading procedures for gecko-inspired controllable adhesives

Area of Science:

• Biomimetics
• Materials Science
• Robotics

Background:

• Biological dry adhesives, like those on gecko feet, demonstrate efficient loading/unloading. Biomimetic dry adhesives lack systematic study of these procedures.
• The influence of approach angle on synthetic dry adhesive performance remains largely unexplored.

Purpose of the Study:

• To investigate how loading and unloading procedures affect preload, adhesion, and shear/friction forces in synthetic dry adhesives.
• To determine the impact of varying approach/retraction angles and shear lengths on adhesive performance.

Main Methods:

• A synthetic adhesive with poly(dimethylsiloxane) fibers was tested using a custom microtribometer.
• 13 approach/retraction angles and 9 shear lengths were systematically varied against a glass substrate.

Main Results:

• Optimal adhesion and friction are achievable across most angles with sufficient shear length.
• Specific approach angles significantly reduced reaction forces during placement.
• A 38-fold increase in adhesion-to-preload force ratio was observed with optimized angles compared to vertical approaches.

Conclusions:

• Loading and unloading procedures, particularly approach angle, are critical for optimizing biomimetic dry adhesive performance.
• Findings provide valuable insights for designing testing protocols and control algorithms for climbing and perching robots.