Electrochemical deactivation of high-strength, catechol-based adhesives incorporated with anhydrous proton and electron conducting elements

Catechol offers switchable adhesion in response to electrochemical redox reaction. However, electrochemistry requires water for effective proton transport, but water weakens adhesive performance. Here, we incorporate proton and electron conducting elements (sulfonic acid-containing monomer and multiwalled carbon nanotube, respectively) into a water-free catechol-based adhesive to create a high-strength adhesive that is also susceptible to electrochemical control. These additions increase the proton and electrical conductivity by over 100-fold. The adhesive also exhibits elevated lap shear adhesion strength (4.6 MPa) to metal substrates and outperforms a commercial epoxy glue. Under mild electrical stimulation (9 V), the adhesive strength decreases by over 90%. X-ray photon spectroscopy confirms the deactivation of the adhesive is achieved by catechol oxidation to its poorly adhesive quinone form. When the adhesive is used to create two adjacent adhesive joints connected by a single metallic substrate, the adhesive can be selectively deactivated without affecting neighboring joint. These results present a promising approach for switchable adhesives with high adhesive performance and precise electrical control. Catechol-based adhesives offer switchable adhesion via electrochemical redox reactions but struggle with water-induced performance issues. Here, the authors enhance a water-free catechol adhesive with sulfonic acid and carbon nanotubes, achieving over 100-fold increased conductivity and superior adhesion, while enabling precise electrical control and selective deactivation.