A batch fabricated biomimetic dry adhesive

TLDR

Natural dry adhesives, such as the gecko’s pad, use multilevel conformal structures of submicron hairs to create large inelastic contact and strong short‑range attractive forces, and recent studies have sought to replicate these terminal hairs. This work presents the first batch‑fabricated multi‑scale conformal system that mimics the natural dry adhesive. The system is fabricated by massively parallel MEMS processing to produce 20–150 µm platforms with slender pillars coated with ~2 µm long, ~200 nm diameter polymer nanorods, and its adhesion is characterized using a newly developed mesoscale nanoindenter technique. Experiments show that the multiscale structure yields significantly improved adhesion, and converting the surface from hydrophilic to hydrophobic further enhances the adhesive performance.

Abstract

The fine hair adhesive system found in nature is capable of reversibly adhering to just about any surface. This dry adhesive, best demonstrated in the pad of the gecko, makes use of a multilevel conformal structure to greatly increase inelastic surface contact, enhancing short range interactions and producing significant amounts of attractive forces. Recent work has attempted to reproduce and test the terminal submicrometre 'hairs' of the system. Here we report the first batch fabricated multi-scale conformal system to mimic nature's dry adhesive. The approach makes use of massively parallel MEMS processing technology to produce 20–150 µm platforms, supported by single slender pillars, and coated with ∼2 µm long, ∼200 nm diameter, organic looking polymer nanorods, or 'organorods'. To characterize the structures a new mesoscale nanoindenter adhesion test technique has been developed. Experiments indicate significantly improved adhesion with the multiscale system. Additional processing caused a hydrophilic to hydrophobic transformation of the surface and testing indicated further improvement in adhesion.