Abstract: Flexible attachment actuators are popular in a wide range of applications, owing to their flexibility and highly reliable attachment. However, their reversible adhesion performance depends on the actual effective contact area and peel angle during operation. Therefore, a good actuator must ensure a uniform and reliable pre-pressure load on an adhesive surface, to increase the effective contact area of the attached surface, thereby maximizing adhesion. This study was inspired by fusion bionics for designing a hierarchical attachment structure with vacuum-adsorption and dry-adhesion mechanisms. The designed structure used the normal force under the negative pressure of a suction cup as a stable source of a pre-pressure load. By optimizing the rigid and flexible structural layers of the attachment structure, a load was applied uniformly to the adhesion area; thus, reliable attachment was achieved by self-preloading. The structure achieved detachment by exploiting the large deformation of a pneumatic structure under a positive pressure. The hierarchical attachment structure achieved up to 85% of the optimal performance of the adhesive surface. Owing to its self-preloading and reliable attachment characteristics, the designed structure can be used as an attachment unit in various complex scenarios, such as small, lightweight climbing platforms and the transport of objects in long, narrow pipelines.

Key words: Multi-mechanism attachment · Self-preloading · Hierarchical structure · Adhesion · Vacuum adsorption