Polymeric Bio‐Inspired Dry Adhesives: Van der Waals or Electrostatic Interactions?

Abstract

With respect to the dry adhesion mechanism that geckos employ for their locomotion, it is commonly accepted that the adhesive performance of synthetic bio‐inspired dry adhesives results from the formation of van der Waals interactions at the tip or side of the dry adhesive fibrils with the substrate they are brought into contact with. However, what has been usually neglected in this connection is that electrostatic interactions may also be developed at the contact between any two materials via the familiar contact electrification (CE) phenomenon. Although CE is common and can have a large influence on interfacial interaction forces, its impact on adhesive properties of synthetic dry adhesives has been overlooked. Even so, recent reports on fabrication of polymeric dry adhesives, which can generate strong adhesion forces relying on electrostatic interactions coming from CE, have brought to light again the idea that charging the surface of dry adhesives, specifically polymeric ones, can play a very crucial role in their adhesive behavior. From this perspective, the main reasons that have caused the lack of attention to this concept and the possible contributions of CE in interfacial interactions of polymeric dry adhesives are thoroughly discussed in this current critical review.