Intelligent lubricating materials: A review

In modern aerospace, nuclear energy, electric power and other high-tech industries, increasingly more requirements are put forward for the enhanced performance and functionality of lubricating materials. In recent years, intelligent lubricating materials and structures with properties on demand and bionic functions by imitating the life system have aroused great interest. The trigger and feedback behaviors of functional ingredients endow intelligent materials with the ability of controllable lubrication. However, there is still a lack of a review that outlines these encouraging results. In this review, the category and lubrication mechanism of the widely used solid lubricants are summarized, and then the novel intelligent lubricating technologies with micro/nanocontainers are comprehensively introduced, including the materials, sizes and synthetic methods of micro/nanocontainers. The stimuli-responsive behaviors and tribological properties of intelligent composites storing liquid lubricants are discussed. On the basis of four kinds of dual functional lubricating materials, the reported preparation strategies and the achieved performance are introduced, and potential functionalization methods are also presented. Finally, the review ends with a brief summary and some future perspectives.