Notes

(1) Engineers are increasingly turning to nature for inspiration when designing and innovating new products and materials. Biomimicry is the study of nature and the modeling of its systems to solve human problems. The term comes from bios, meaning “life,” and mimesis, meaning “to imitate.” The study of plants, animals, and microbes demonstrates that nature has already solved many of the design problems that engineers face. By mimicking those solutions, humans can get important clues to solving our own problems.

(2)The recent trend in research toward developing self-healing materials provides a case study in biomimicry. One of the first successful self-healing technologies cleverly mimics the healing process of human skin with a polymer1 plastic. When our skin’s outer layer is cut, tiny blood vessels deliver substances to the site of the damage that help with healing. Similarly, when the self-healing polymer material is cut, microscopic capsules, or microcapsules, embedded in it release a healing agent.






(3) In testing, capsule-based self-healing systems have been able to recover 75 percent of their original strength after damage. Subsequent research has refined and expanded on the capsule-based technology. For example, researchers have now developed a microcapsule-infused metal that can be used to make self-healing electric circuits.

(4) While capsule-based technology shows great promise, it does have its limitations. Though the technology could save money over time, initial costs of developing the materials are high. The materials do not regain 100 percent of their original strength. In addition, a capsule-based self-healing material is limited by the amount of healing agent that can be embedded in it. Once the healing agent runs out, the material can no longer repair itself.

(5) A second self-healing technology in development solves this problem by adopting characteristics of the human vascular system. This body system includes capillaries, veins, and arteries that send healing blood to the site of damage. The ingenious microvascular self-healing technology mimics this system by employing a three-dimensional network of microscopic channels that can be replenished with healing agent. When damage occurs, nearby channels automatically deliver the required amount of healing agent, which hardens and seals a crack.

(6) One vascular material under development may someday prevent fracturing in aircraft. The engineered vascular material is a composite with an embedded network of microscopic glass tubes that deliver healing agent to seal small cracks before they cause larger problems. In testing, the microvascular composite material was able to heal up to 30 times in a row, and restore up to 90 percent of the material’s original strength. The challenge is now to develop a way to manufacture such sophisticated networks and to make sure the healing fluid can flow freely.

(7) Some researchers are looking to another aspect of the vascular system for innovation in self-healing materials. They are interested in a detailed understanding of how blood clots. When human blood forms a clot, rolled-up molecules become unrolled and begin to stick together, eventually plugging up a wound or tear. The researchers discovered that the speed of the fluid flowing around the molecules is what causes them to unroll. They are now working on mimicking the blood-clotting molecules, to develop a new self-healing technology.

(8) In addition to skin and vascular systems, bone has inspired its own direction in self-healing technology. In nature, bone can detect and stop its own damage, as well as repair itself back to its original strength. A self-healing material currently being researched can also detect and heal itself, recovering up to 96 percent of its original toughness. This bone-based technology uses shape-memory polymers with an embedded fiber-optic network. Infrared laser light is transmitted through the fiber-optic system to initiate the healing mechanism in the material.

(9) Though still developing, the field of self-healing technology is advancing at a rapid pace. Perhaps the solutions to scientists’ final hurdles in bringing these technologies to fruition await us in nature.