Multiscale Modeling of Carbon Nanotube Adhesion for Dry Adhesives

Geckos have extraordinary ability to move on vertical surfaces and ceilings. The secret of the climbing ability stems from their foot pads, a special hierarchical hairy structure. Mimicking such structure would lead to dry adhesives for many applications. Recent experiments showed that the adhesion of multiwalled carbon nanotubes is larger than that of a gecko foot-hair. To explore the adhesive mechanisms of the nanotubes, we have developed a multiscale approach to simulate the adhesion process of carbon nanotubes. A molecular dynamics method is used to simulate the deformation and damage of the nanotubes when contacting with a rough surface at atomic scale. A coarse graining method is developed to predict the interactions and adhesion of a larger scale nanotube array. The parameters used in the coarse graining method are determined by the detailed molecular dynamics. The preliminary results show that the nanotube bending under preapplied pressure increases the contact area and therefore enhances the adhesion. The nanotube breakage during pre-loading will reduce the adhesion in post cycles. These results are consistent with experiments found in the literature.