Papers by Keyword: Dry Adhesive

Abstract: Vertically aligned carbon nanotubes (VACNT) arrays were designed to mimic natural foot-hairs of geckos in order to elucidate the adhesion mechanism. We fabricated and systematically investigated adhesive properties of the VACNT arrays with different top structures. Balancing the gas ratio and pressure used for low pressure chemical vapor deposition (CVD) processing controls the top structures of VACNT arrays which determine the strength of adhesion. Their contact behaviors were observed using a scanning electron microscope (SEM). The VACNT arrays attached the target surface by different contact behavior based on the different top structures. The different contact behavior varied adhesive properties of VACNT arrays. VACNT arrays with free top structure present higher adhesion strength due to the side contact with target surface, which indicated that the top structure is an important factor enabling generation of a strong adhesion. These results present clear implications for the role of top structures in VACNT arrays based synthetic gecko systems, which is important for fabrication of gecko-inspired dry adhesives.

Abstract: Since early this decade, investigations into how geckos achieve their remarkable adhesive properties, have determined that multi-scale compliant systems can allow geckos to attach to nearly any surface through Van der Waals forces. Microscopic hairs on the bottom of gecko feet can make intimate contact over large areas, and allows relatively weak Van der Waals forces to produce significant adhesion on the macroscale. Over the past five years, microfabrication technology has been used to replicate these multi-scale compliant mechanisms, using silicon or polymers to reproduce microscale rods or cantilevers to produce what is known as a dry adhesive. What is more difficult is creating the nanoscale compliant systems that create most contact areas in gecko feet. This work examines how a well known problem in reactive ion etching processes, RIE "grass" can be used to great effect to alter surface morphology on the nanoscale for nearly any polymer. Identical etching parameters in the presence of different elements, like gold or aluminum, can result in radically different surface morphologies and material behaviors, potentially allowing both adhesive and non-adhesive areas to be formed in a single material. This technique is potentially the easiest and fastest way to produce nano-compliant systems for use with dry adhesives.