Microcapsules in self-healing materials: a review

Abstract This review article focuses on autonomous self-healing systems based on microcapsules, with a particular emphasis on capsule synthesis processes, wall material selection, and mechanical and chemical properties. The article focusses on the microencapsulation of reactive repair agents, analysing the most important achievements published since 2015. The variety of encapsulation methods physical, physicochemical, and chemical are discussed in detail, with an emphasis on polymerisation as the most commonly used technique for obtaining durable coatings. A wide range of core materials that can initiate different repair reactions, depending on the application, is also considered. It is indicated how the choice of capsule coating should correspond not only to the operating conditions and stresses in the material, but also to the process of introducing the capsules into the matrix. Examples of five self-repairing systems are described and illustrated, pointing to their application in various fields of materials engineering, from construction materials, cements, and asphalts to advanced polymer coatings. The article highlights the potential of microcapsules as universal carriers of repair agents in diverse self-healing systems.