Mechanics of electroadhesion by polycation interfacial bridging: sticky electrophoresis, ionic complexation and chain entanglement

Abstract

Abstract An e-GLUE is a polymer network containing interpenetrating polycations, which can bond the anionic network of mucosa by polycation interfacial bridging under an electric field. This paper formulates a theoretical model to study such electroadhesion by electrophoresis of polycations, ionic complexation between polycations and the anionic network, and polycation-network entanglement. We use a diffusion- drift model coupled with a Bell-like field-dependent chain friction to describe the sticky electrophoresis of polycations in the anionic network. We determine the formation of ionic bonds by local availability of cations and anions over the penetration depth. To debond, a force must either pull polycations out from the e-GLUE network or dissociate them from ionic complexes first and then pull out from the anionic network. We model chain pullout as a viscous drag against water. Finally, adhesion strength is calculated by summing the debonding force for each polycation per unit area across all chains. Our model quantitatively links electric field strength, applied duration, polycation chain length, friction coefficient and cation concentration to polycation electrophoresis kinetics, ionic bond formation and adhesion strength. We further conduct electroadhesion tests, and our model predicts well with the experimental data. Lastly, we discuss the use of the model to guide the e-GLUE design.