Integrated damage sensing and self-healing in polymers and composites: Progress and opportunities

Biological materials self-regulate throughout their lifetime, controlling cellular proliferation and mitigating damage for greater longevity through a coordinated effort of sensing and self-repair. In contrast, synthetic materials generally serve a predetermined purpose and lack the autonomic control necessary for environmental adaptability. Polymeric materials can greatly benefit from bioinspired attributes to last longer and offset their negative environmental impacts from petroleum precursors and end-of-life waste accumulation. Fiber-reinforced polymer (FRP) composites, in particular, which are increasingly used in large structures (e.g., aircraft, wind turbines) and inherently difficult to recycle given their heterogeneous makeup, are well poised to further global sustainability efforts. However, to date, intelligent material systems with integrated damage sensing and self-healing functionality are largely limited to soft polymers. In this article, we examine sensing/healing attributes in living materials and compare them with synthetic strategies that have evolved over the past 20+years. We highlight fundamental features to attain autonomous mechanical stasis and provide key insights that reveal immediate opportunities for overcoming outstanding challenges.