With the demand for more resilient and sustainable products, researchers have focused on self-repairing materials, which can withstand minor abuse and return to their original physical condition. Such materials would not only outlast their conventional counterparts, but also require less substance in their manufacturing, says Carolyn Dry, president of Natural Process Design (NPD). “The fact that structural damage can go undetected … means that some products are over-engineered. However, substances that can provide information about their internal stresses—as well as trigger reliable self-healing properties—allow manufacturers to be more confident in using lighter weight materials.”
Airplane components made from NPD’s ultralight graphite polymer composite, for example, weigh 30 percent less than standard components and also help reduce fuel consumption. The Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign is also pioneering self-healing materials. Aerospace engineering professor Scott White has created polymers embedded with a chemical trigger and a microencapsulated healing agent. When the polymer is overstressed and cracks, it autonomically releases a healing agent into the rupture. Currently, it is limited to a onetime fix; White and his team are exploring a new generation of materials embedded with microvascular networks that can repeatedly self-heal. Potential building applications include elements in façades and high-traffic areas.
Stanford University chemical engineering professor Zhenan Bao and her team have invented a conductive, self-healing plastic capable of multiple repairs. The autonomic polymer, which incorporates nickel particles, can detect and communicate changes in pressure. As a result, the plastic behaves like human skin in terms of sensory capabilities. The team is working on developing a transparent version of the material, for potential use in touchscreens and robotics.
Though self-repairing materials’ sustainability and resiliency are promising, these goals are also in conflict. To maximize resource savings, they must eliminate the redundant matter intended for safeguards, an earmark of resilient design. Indeed, Dry’s idea of materials that relay their stresses would succeed only if facility managers had a more active relationship with their buildings than what now exists. While a built environment that acts like living tissue holds much promise, it brings with it many uncertainties.