Adhesion enhancement of a biomimetic dry adhesive by means of an increase to the Hamaker constant via nanocomposite formation

A novel method to increase the van der Waals adhesion of a gecko-inspired polymeric fibrillar dry adhesive through an increase of the polymer’s Hamaker constant is presented. Different metal nanoparticles (NPs) were embedded in the polydimethyl siloxane (PDMS) dry adhesive to create a nanocomposite. The successful process involved the in-situ synthesis of Au nanoparticles within the mushroom caps of the PDMS microfibrils to enhance adhesion. Successful synthesis of the Au NPs was analyzed using Ultraviolet-Visible Spectrophotometry. To quantify the adhesion enhancement, a pull-off force test was employed to compare the adhesive samples before and after the Au nanoparticles were synthesized. The experiments performed indicate an adhesion improvement of up to 2.2x as a result of the increase in the Hamaker constant of the dry adhesive mushroom caps. A model based on the Hamaker approximation to van der Waals forces is evaluated which is in good agreement with the experimental measurements.