Charge Contribution to the Adhesion Performance of Polymeric Microstructures

Strong attachment of many insects with microstructured attachment pads is due to the Van der Waals interactions or/and the capillary forces between the pads and substrates. To establish initial contact between two surfaces a certain normal force should be applied. The presence of the charges on surfaces could facilitate or impede the initial contact formation. In this study, forces appearing due to the contact electrification of microstructured material mimicking beetle adhesive pads were measured and their influence on the contact formation was discussed. The experiments have clearly demonstrated that static charges contribute to an initial contact establishment in materials with the mushroom-shaped microstructure, whereas Van der Waals interactions or/and capillary forces have the main contribution at pull-off. A simple model was successfully used for data analysis and extraction information about the charge distribution. The effect of the jump-in due to the electrostatic interaction has to be considered during the development of further implementation of biologically inspired microstructured adhesives.