Gecko-inspired adhesive structures for amphibious soft robot locomotion.

Over the years, efforts in bioinspired soft robotics have led to mobile systems that emulate features of natural animal locomotion. This includes combining mechanisms from multiple organisms to further improve movement. In this work, we seek to improve locomotion in soft, amphibious robots by combining two independent mechanisms: sea star locomotion gait and gecko adhesion. Specifically, we aim to test and compare various microstructures using different soft polymers to determine the optimal material with the corresponding microstructure configuration. We tested hemispherical, cylindrical and wedge-shaped microstructures made of PDMS and polyurethane to determine the adhesion on glass, acrylic, wood and metal surfaces. We determined the optimal geometric configuration for each type of microstructure by mathematically modeling the adhesion response of various geometric configurations. The gecko-inspired adhesives were subsequently subjected to experimentation on a compliant, pneumatically actuated limb, intended for integration into a soft robot inspired by sea stars. These adhesives, drawing inspiration from gecko adhesive structures, demonstrated a significant augmentation in adhesion properties across different substrates and enabled the robot to ascend inclines with a steepness of up to 25° and to maintain a stable grip on slopes inclined at 51° ± 6° under static conditions.