Scientists from Northwestern University in Illinois and the Kensey Nash corporation have developed a new adhesive that combines the dry adhesion strengths of gecko feet with the wet ahesive strengths of mussel feet. The material, called Geckel, has proven to be a strong and reversible adhesive on dry and wet surfaces, a feat not demonstrated by either geckos or mussels. Gecko feet are able to generate adhesion by taking advantage of a phenomenon called 'contact splitting.' The enormous surface area of the split-ended hairs on the lizards' feet creates a disproportionately large region of attraction (based on van der Waals forces) compared to the aparent surface area of the feet. The researchers mimicked this nanostructure by synthesizing arrays of silicone pillars on a solid substrate. However, like gecko feet, this synthetic surface failed to produce adhesion when wet. Mussels are thought to produce adhesives that rely on polymer of an amino acid called DOPA. When synthetic DOPA polymer was applied to the surface of the silicone pillars, it was able to generate adhesion even when wet. The biomimetic hybrid material maintains adhesion over 1000 contact/release cycles even when wet. The researchers hope that this revolutionary new material will be useful for the production of new bandages and transdermal drug-delivery patches. They would be impervious to water and extremely sticky yet capable of being removed when they are no longer needed.
Most adhesives lose effectiveness when wet. In addition, there are few adhesives that maintain activity over the course of repeated contact cycles. Geckel nano-adhesive could be superior to conventional adhesives for certain applications.