Self-healing materials have been developed since the 1990s and are currently used in various applications. Their performance in extreme environments and their mechanical properties have become a topic of research interest. Herein, we discuss cutting-edge self-healing technologies for hard materials and their expected healing processes. The progress that has been made, including advances in and applications of novel self-healing fiber-reinforced plastic composites, concrete, and metal materials is summarized. This perspective focuses on research at the frontier of self-healing structural materials.

Advanced physical sensors based on carbon nanotube/polydimethylsiloxane (CNT/PDMS) nanocomposites have recently attracted much attention for potential applications such as wearable and flexible electronic devices. In this work, a CNT/PDMS sponge was fabricated and their capacitive as well as resistive response was investigated by impedance characterization with an equivalent circuit model. The newly defined gauge factor, which considers simultaneously both the piezocapacitive and piezoresistive effects of CNT/PDMS sponge sensors, showed a significantly improved sensitivity. This work provides important information for a better understanding of CNT/PDMS nanocomposites and their sensing performance.

In this paper, the anticipated challenges and future applications of self-healing composite materials are outlined. The progress made, from the classical literature to the most recent approaches, is summarized as follows: general history of current self-healing engineering materials, self-healing of structural composite materials, and self-healing under extreme conditions. Finally, the next stage of research on self-healing composites is discussed.