# Advanced Micro/Nanocapsules for Self-Healing Coatings
## 5 Types of Self-Healing Capsules
### Application-Based Classification of Self-Healing Capsules  
One of the key factors to consider is the application. Based on their structure, microcapsules can be classified into several categories. For instance, single-walled single nuclei and single-walled multiple nuclei microcapsules offer unique advantages in dual-targeted drug delivery via sonochemical methods [82]. These innovative structures allow for precise and efficient delivery of healing agents to the damaged areas, enhancing the overall healing process. Moreover, the utilization of microcapsule self-healing technology has shown promising results in the field of cement-based materials [83]. Researchers are exploring the potential of these capsules for future applications, indicating a growing interest in this advanced technology. Another crucial aspect of self-healing capsules is the triggering mechanism that initiates the healing process. Extrinsic self-healing composites stand out for their automatic recovery capabilities when damaged, drawing inspiration from biological systems that exhibit natural healing properties [84]. Within this category, there are two major groups: autonomic and non-autonomic self-healing materials. Autonomic materials, in particular, have the remarkable ability to heal themselves without the need for external intervention [85]. This self-sustainability makes them highly desirable for various applications where continuous maintenance is impractical. By understanding the different triggering mechanisms, researchers can tailor self-healing capsules to specific requirements, maximizing their effectiveness. The material compatibility of self-healing capsules plays a significant role in determining their performance and durability. Inorganic capsules, such as those based on magnesium oxide, have shown great promise in enhancing the healing potential of various materials [86]. Researchers have developed innovative techniques for preparing and encapsulating powder mineral pellets, further expanding the applications of inorganic capsules [86]. By focusing on the mineralogy of the inner core and granule strength, scientists can optimize the compatibility of these capsules with different matrices, ensuring long-lasting and effective healing properties [86]. This attention to detail in material compatibility is essential for advancing the field of self-healing technology and unlocking new possibilities for sustainable infrastructure development. The classification of self-healing capsules based on the application method, triggering mechanism, and material compatibility provides a comprehensive framework for understanding their diverse functionalities. By exploring the nuances of each type of self-healing capsule, researchers can continue to innovate and develop cutting-edge solutions for a wide range of industries. The potential of self-healing capsules to revolutionize material maintenance and restoration is vast, making them a vital area of research and development in the modern era. The integration of self-healing agents into coatings has emerged as a revolutionary technique with substantial implications for both environmental sustainability and long-term durability. Among the key areas of focus, the ability of these coatings to autonomously repair damages plays a crucial role in mitigating corrosion, which not only prolongs the lifespan of metal structures but also significantly reduces maintenance costs and environmental impact [25]. For instance, advancements in self-healing polymeric materials have demonstrated significant potential across various industries by enhancing the durability of protective applications, thus reducing the frequency of replacements and the associated waste. Furthermore, the development of highly optimized self-healing designs in organic coatings has shown marked improvements in performance, reflecting the ongoing evolution from foundational research to advanced practical applications.