Switchable Adhesion for Nonflat Surfaces Mimicking Geckos' Adhesive Structures and Toe Muscles

Area of Science:

• Biomimetics and Robotics
• Materials Science and Engineering

Background:

• Gecko-inspired dry adhesion is crucial for soft grippers and wall-climbing robots.
• Current technologies struggle with stable adhesion on nonflat surfaces.
• Geckos utilize adhesive structures and muscle stiffness for versatile climbing.

Purpose of the Study:

• To develop a hierarchical adhesive structure for high and switchable adhesion on nonflat surfaces.
• To mimic gecko's epidermal adhesive structures, toe muscles, and electromyographic signals.
• To enhance adhesion performance beyond conventional structures.

Main Methods:

• A three-layer adhesive structure was designed: mushroom-shaped top layer, thermoplastic polyurethane middle layer for stiffness modulation, and an electrothermal film bottom layer.
• Tunable structural stiffness was achieved by adjusting voltage.
• The adhesive force was measured and compared to conventional structures.

Main Results:

• The hierarchical adhesive demonstrated increased adhesive force by 1 to 2 orders of magnitude compared to conventional structures.
• The tunable stiffness allowed for effective attachment and detachment functions.
• A gecko-inspired soft gripper successfully transported surfaces with varying features.

Conclusions:

• The proposed hierarchical adhesive structure offers high and switchable adhesion on nonflat surfaces.
• This technology has significant potential for industrial automation and daily-life applications.
• The design effectively mimics gecko locomotion principles for advanced robotic grippers.