Self-healing materials

BBC reports: [edited]

New developments in self-healing technology have been pioneered by Prof Nancy Sottos and her team at the University of Illinois Urbana-Champaign, involving the impregnation of plastics with a fine network of channels, each less than 100 millionths of a metre in diameter, that can be filled with liquid resins.

These "micro-vascular" networks penetrate the material like an animal's circulation system, supplying healing agent to all areas, ready to be released whenever and wherever a crack appears.

Limitations still blight this technology however, as the healing process relies on the slow wicking action and diffusion of the healing agent into a crack.

The researchers have therefore taken another lesson from biology to improve on the self-healing material's performance. "In a biological system, fluids are pumping and flowing," said Prof Sottos, so they have devised a way to actively pump fluids into their micro-vascular networks.

Syringes on the outside of the material put healing fluids under pressure so that when a crack appears, a constant pressure drives the fluid into the cracks.

In the experiments that Prof Sottos' team carried out, two parallel channels are created in a plastic and pumped with a liquid resin and a hardening chemical that triggers the resin to solidify.

"Micro-capsule technology will enable damaged openings around 50-100 millionths of a metre to be filled, whereas pumping healing agents through a micro-vascular network can fill major cracks up to a millimetre across," said Prof Sottos.
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