Artificial system inspired by climbing mechanism of galium aparine fabricated via 3D laser lithography

Abstract

In this work, we present an artificial dry adhesive system inspired by the leaf-climbing mechanisms in Galium aparine. Among the different species of climbing plants, G. aparine shows a unique capability of adhesion to a wide range of roughness and stiffness objects, mainly via its leaves, using microscopic hooks for the physical interlocking. The adaxial (upper) and abaxial (lower) leaf surfaces differ significantly in attachment properties, which depend on the direction of the applied force (ratchet-like mechanism). In order to mimic this adhesive behavior, we designed artificial abaxial and adaxial leaf hooks by extracting the morphological parameters from the natural structures. We fabricated artificial hooks at different scales (1:1, 1:2, 1:4) using Direct Laser Lithography (DLL), a technique that allows a rapid prototyping of 3D microstructures. The adhesion of the artificial systems was tested on a polyester tissue substrate, obtaining adhesive forces comparable or higher than the natural counterpart. This biomimetic approach can open new opportunities to understand nature through artificial investigations and lead to several applications in the fields of robotics and space technology.