Reversible Adhesive Bio-Toe with Hierarchical Structure Inspired by Gecko

Abstract

The agile locomotion of adhesive animals is mainly attributed to their sophisticated hierarchical feet and reversible adhesion motility. Their structure–function relationship is an urgent issue to be solved to understand biologic adhesive systems and the design of bionic applications. In this study, the reversible adhesion/release behavior and structural properties of gecko toes were investigated, and a hierarchical adhesive bionic toe (bio-toe) consisting of an upper elastic actuator as the supporting/driving layer and lower bionic lamellae (bio-lamellae) as the adhesive layer was designed, which can adhere to and release from targets reversibly when driven by bi-directional pressure. A mathematical model of the nonlinear deformation and a finite element model of the adhesive contact of the bio-toe were developed. Meanwhile, combined with experimental tests, the effects of the structure and actuation on the adhesive behavior and mechanical properties of the bio-toe were investigated. The research found that (1) the bending curvature of the bio-toe, which is approximately linear with pressure, enables the bio-toe to adapt to a wide range of objects controllably; (2) the tabular bio-lamella could achieve a contact rate of 60% with a low squeeze contact of less than 0.5 N despite a ±10° tilt in contact posture; (3) the upward bending of the bio-toe under negative pressure provided sufficient rebounding force for a 100% success rate of release; (4) the ratio of shear adhesion force to preload of the bio-toe with tabular bio-lamellae reaches approximately 12, which is higher than that of most existing adhesion units and frictional gripping units. The bio-toe shows good adaptability, load capacity, and reversibility of adhesion when applied as the basic adhesive unit in a robot gripper and wall-climbing robot. Finally, the proposed reversible adhesive bio-toe with a hierarchical structure has great potential for application in space, defense, industry, and daily life.

Gecko-Inspired Controllable Adhesive: Structure, Fabrication, and Application

“…Therefore, the gecko controls the hierar chical adhesion system through the movement of its feet, and the hierarchical adhesio system closely contacts and separates from the wall under macroscopic control, thereb achieving controllable adhesion and detachment. [44,45] were adapted through open access permission).…”

“…Although the above gecko-inspired adhesive can generate a strong adhesion force its adhesion force is not anisotropic, meaning that it cannot realize controllable adhesion Distinguished from traditional adhesives, the controllability of adhesion force and frictio force is the key feature of gecko-inspired controllable adhesive surface design, which i [44,45] were adapted through open access permission).…”

Bioinspired Rigid–Flexible Coupled Adaptive Compliant Motion Control of Robot Gecko for Space Stations

“…Conversely, whe flating (negative pressure) the foot, the toes curl upwards, facilitating detachment. I inoperative state, the toes return to their natural position, that is, atmospheric pres For detailed design and analysis of the biomimetic foot, please refer to the given refer [39]. It shall be mentioned that our team members are constructing a liquid-driven sy using ionic liquids as the fluid medium to meet the vacuum and extreme temper conditions of space stations.…”