Bio‐Inspired Adhesive with Reset‐On Demand, Reuse‐Many (RORM) Modes

Abstract Development of tough, reusable adhesives is important, but remains a major challenge, especially in water. A tough reusable adhesive that resets entirely to its virgin condition when needed is reported using caffeic acid. Here, caffeic acid is employed as adhesive moiety to achieve such the functions due to its dual characteristics: an adhesive moiety from mussel‐inspired catechol and a photo‐reversible crosslink from cinnamic acid. Adhesion involves a two‐step process. First, the caffeic acid‐functionalized polymer is applied to the adherend, followed by UV irradiation (peak wavelength of light‐emitting diode, λ P : 365 nm) to form a durable pre‐applied adhesive (PAA) layer through crosslinking among the caffeic acid moieties. Second, thermal activation of the PAA layer ensures repeated adhesion to a variety of adherends ( R euse‐ M any mode). The cyclic dimer of the caffeic acid moiety is de‐crosslinked by UV irradiation at λ P : 254 nm. This allows the complete removal of the adhesive residues from the adherends when the adhesive is no longer needed ( R eset‐ O n demand mode). Furthermore, using magnetic nanoparticles, the caffeic acid‐functionalized polymer can be activated remotely under water by magnetic induction heating. This study paves the way for the rational design of bio‐inspired adhesives that outperform nature using plant‐derived raw materials.