Detectable Adhesives: Nondestructive Detection of Adhesion

Abstract Metal‐to‐metal adhesives are vital across diverse sectors including automotive, aerospace, and industrial assembly. However, traditional adhesion detection methods are mainly based on the fracture mechanism, posing challenges for nondestructive detection. Here, a nondestructive method that leverages electrical signals to monitor the adhesion state of metal interfaces in real‐time is presented. The approach utilizes detectable adhesives (DA) synthesized from poly(ionic liquid) (PIL), which not only exhibit robust adhesion properties (4.9 MPa) but also function as ionic conductors. By correlating changes in capacitance and resistance with the adhesive state, the method allows for in situ monitoring of the curing process, prediction of adhesion strength, and early detection of potential failures. This dual‐sensing capability, combining electrical and mechanical aspects, enhances understanding of adhesive behavior in diverse conditions, presenting a fresh approach for digitally transforming adhesive technologies.