Grand challenges in the design and manufacture of vascular self-healing

This perspective details the grand challenges of designing and manufacturing multifunctional materials to impart autonomous property recovery. The susceptibility of advanced engineering composites to brittle fracture has led to the emergence of self-healing materials. This functionality has been demonstrated in bulk polymers and fibre-reinforced composites; most recently through the addition of vascular networks into the host material. These network systems enable the healing agents to be transported over long distances and provide a means by which both the resin and hardener can be replenished, thus overcoming the inherent limitations of capsule-based systems. To date, vascule fabrication methods include machining, fugitive scaffold processes, a lost-wax process and the vaporisation of sacrificial components, but recent developments in additive manufacturing (AM) technologies have paved the way for more efficient, bio-inspired vascular designs (VDs) to be realised. This perspective reviews the current progress in vascular self-healing and discusses how AM technologies and new design methods can be exploited in order to fabricate networks that are optimised for fluid transport and structural efficiency. The perspective culminates in the discussion of eight grand challenges across three thematic areas: ‘VD’, ‘Healing Chemistry’ and ‘AM’, that are likely to have major breakthroughs and socio/economic impact as these technologies are developed further in the next 10–15 years.