Bio‐inspired Dry Adhesives: Contact Electrification and Electrostatic Interactions

Abstract

This article discusses contact electrification and related electrostatic forces as they pertain to the adhesive properties of gecko foot pads and gecko‐inspired adhesives. Following an introduction to gecko adhesion and gecko‐inspired adhesives, fundamentals of contact electrification‐driven electrostatic interactions are discussed, along with electrostatic phenomena that can affect these interfacial interactions. Particular attention has been given to three special phenomena: electrostatic discharge, surface charge leakage, and charge penetration into the matrix of fibrillar dry adhesives. Through the analysis of the effects of these three phenomena, it is demonstrated how the general characteristics of fibrillar dry adhesives, such as strong attachment, easy detachment, and self‐cleaning, can be considered and explained in terms of contact electrification‐driven electrostatic interactions of these materials. In this connection, the effects of many factors (electrical conductivity, dielectric properties, and geometrical properties) on contact electrification‐driven electrostatic interactions of fibrillar dry adhesives have also been discussed. The ensuing discussion on the magnitude of electrostatic adhesion forces that fibrillar dry adhesives can develop via contact electrification has been carried out with respect to three key parameters (surface roughness, humidity, and tip geometry) and the effects that these can have on the strength of the contact electrification‐driven electrostatic interactions of gecko and gecko‐inspired adhesives.

Surface Adaptable and Adhesion Controllable Dry Adhesive with Shape Memory Polymer

“…[ 40 ] This principle facilitates the gecko's fast locomotion while walking up and down onto diverse surfaces despite the gecko toe's formidable adhesion strength. [ 41 ] In this study, we developed a novel dry adhesive having a facile attaching/detaching mechanism, denoted as the SMP‐based switchable dry adhesive (SSA), as inspired by the gecko's adhesion switching behavior inducing crack propagation via angle control. This mechanism has the capability to store a temporary shape modified by an external force and is able to regain the original properties by the recovery effect with the thermal stimulus (Figure S1, Supporting Information).…”