Bio-Inspired Hierarchical Polymer Fiber-Carbon Nanotube Adhesives

摘要

Natural adhesive systems, consisting of pads covered by dense assemblies of high aspect ratio branched adhesive setae, (Figure 1a) excel in terms of adhesive strength on nearly any surface. Facile contact release is achieved by spatulae at the seta tips that are inclined with respect to the setae axis, requiring a normal preload and shear to establish adhesive contact and enabling low-resistance contact release by peel-off. While technologically valuable, dense hierarchical fibrillar adhesives are difficult to manufacture and no scalable approaches yet exist to create the required spatulae asymmetry. Here we demonstrate the manufacture of biomimetic hierarchical nano-structures based on polymer micro-pillar arrays topped with densely packed, vertically aligned carbon nanotubes (CNTs), which closely resemble gecko toe-pads. A permanent spatula-like asymmetry is introduced into the CNT assembly during a first adhesion-release cycle consisting of a normal preload and a shear motion. The shear adhesion forces of these deformed hierarchical CNTs/polymer pillar arrays on smooth and rough surfaces were found to be considerably higher than those of non-structured (i.e., plain) CNT forests, caused by the con-formal attachment of the multilevel adhesive elements to the coarse surface topography, energy dissipation during the deformation of the polymer pillars and the increased contact area provided by the inclined CNTs.