Biomimetic surfaces with controlled direction-dependent adhesion

Abstract

We propose a novel design of a biomimetic micro-structured surface, which exhibits controlled strongly direction-dependent adhesion properties. The micro-system consists of parallel elastic wall-like structures covered by a thin layer. Numerical calculations have been carried out to study the adhesive properties of the proposed system and to provide design criteria with the aim of obtaining optimized geometries. A numerically equivalent version of the double cantilever beam fracture experiment is, then, simulated by means of finite element analysis to investigate the anisotropic adhesion of the structure. We find that, because of inherent crack trapping properties of these types of structures, the wall-like geometry allows us to strongly enhance adhesion when the detachment direction is perpendicular to the walls. On the other hand, when the detachment occurs parallel to the walls, the system shows low adhesion. This controlled direction-dependent adhesive property of the proposed structure solves one of the key problems of biomimetic adhesive surfaces, which usually show very strong adhesion, even larger than biological systems, but are not suitable for object manipulation and locomotion, as detachment always occurs at high loads and cannot be controlled.

Direction-dependent adhesion of micro-walls based biomimetic adhesives

“…(20) fails and the critical moment needs to be calculated taking into account the periodicity of G with the crack extension. In such case, as shown in [14], crack propagation occurs without interruption only when the minimum value of the energy release rate G min exceeds the work of adhesion γ Δ . So the critical bending moment is obtained by enforcing G min γ = Δ .…”

“…In [14] it is shown that when the crack propagates perpendicularly to the wall-like structures, the periodic geometry of the system will force the energy release rate G to vary periodically with the crack extension, with period equal to the wall spacing λ.…”

“…In order to make this type of architecture suitable for applications where object manipulation and locomotion are required, a slight modification has been proposed in [14]. The new system is constituted by parallel wall-like structures topped with a terminal thin film, so as to get a preferential direction of adhesion.…”

“…In the present work, we extend the study of Afferrante and Carbone [14] to the case of an external moment forming a generic angle with the walls, with the aim to understand how this angle affects the adhesion capacity of the system. Fig.…”

Non-linear double-peeling: Experimental vs. theoretical predictions

“…Starting with research [8][9][10][11][12][13][14][15][16][17][18][19] on the adhesion behavior of lizards (like gecko, for instance) and arthropods (like beetles or spiders), a great deal of experimental [20][21][22][23][24] and theoretical [25][26][27][28][29][30][31] work has been done to study the mechanism of adhesion and detachment of natural systems.…”