Dry Adhesion of Artificial Gecko Setae Fabricated via Direct Laser Lithography

Abstract

Biomimetics has introduced a new paradigm: by constructing structures with engineered materials and geometries, innovative devices may be fabricated. According to this paradigm, both shape and material properties are equally important to determine functional performance. This idea has been applied also in the field of the microfabrication of smart surfaces, exploiting properties already worked out by nature, like in the case of self-cleaning, drag reduction, structural coloration, and dry adhesion. Regarding dry adhesive properties, geckos represent a good example from which we take inspiration, since they have the extraordinary ability to climb almost every type of surface, even smooth ones, thanks to the hierarchical conformation of the fibrillary setae in their toe pads. Due to this design, they can increase the area of contact with a surface and thus the amount of attractive van der Waals forces. While reproducing with artificial materials the same functional morphology of gecko’s pads is typically not achievable with traditional microfabrication techniques, recently Direct Laser Litography offered new opportunities to fabrication of complex three-dimensional structures in the microscale with nanometric resolution. Using direct laser lithography, we have fabricated artificial gecko setae, reproducing with unprecedented faithfulness the natural morphology in the same dimensional scale. Adhesion force of artificial setae toward different surfaces have been tested in dry condition by means of a dedicated setup and compared with natural ones.