Fabrication and characterization of hierarchical nanostructured smart adhesion surfaces

The mechanics of fibrillar adhesive surfaces of biological systems such as a Lotus leaf and a gecko are widely studied due to their unique surface properties. The Lotus leaf is a model for superhydrophobic surfaces, self-cleaning properties, and low adhesion. Gecko feet have high adhesion due to the high micro/nanofibrillar hierarchical structures. A nanostructured surface may exhibit low adhesion or high adhesion depending upon fibrillar density, and it presents the possibility of realizing eco-friendly surface structures with desirable adhesion. The current research, for the first time uses a patterning technique to fabricate smart adhesion surfaces: single- and two-level hierarchical synthetic adhesive structure surfaces with various fibrillar densities and diameters that allows the observation of either the Lotus or gecko adhesion effects. Contact angles of the fabricated structured samples were measured to characterize their wettability, and contamination experiments were performed to study for self-cleaning ability. A conventional and a glass ball attached to an atomic force microscope (AFM) tip were used to obtain the adhesive forces via force-distance curves to study scale effect. A further increase of the adhesive forces on the samples was achieved by applying an adhesive to the surfaces.

Figure optionsDownload high-quality image (68 K)Download as PowerPoint slideHighlights
► Nanostructured surface may show low or high adhesion depending on fibrillar density.
► Current research uses a patterning technique to fabricate smart adhesion surfaces.
► Oriented fibers of 100 and 600 nm diameter exhibited gecko effect due to high density.
► Oriented fibers of 5 and 14 μm diameter exhibited Lotus effect due to smaller density.
► The bending and buckling behaviors of the fibers were observed.