September 29, 2011
New Self-Healing Fluids Could Prevent Cracks In Material
University of Illinois researchers have found a way to pump self-healing fluids around a material similar to an animal's blood circulation.
Self-healing materials have been the focus of many scientists for close to a decade, all hoping to reduce the risks and costs of cracking and damage in a wide range of materials.Researchers have taken different approaches in creating self-healing materials, but this is the first that took a page out of nature itself.
Professor Nancy Sottos and her team at the University of Illinois Urbana-Champaign pioneered "micro-vascular" networks that penetrate the material similar to an animal's circulation system.
“Fluid flow in these natural vascular systems is typically driven by a pressure gradient induced by the pumping action of a heart, even in primitive invertebrates such as earthworms," the team wrote in a paper for the Royal Society journal Interface
The new development helps supply healing agents to all areas, ready to be released whenever a crack appears.
Syringes on the outside of the material help put healing fluids under pressure so when a crack appears, a constant pressure helps to drive the fluid into the cracks.
"Micro-capsule technology will enable damaged openings around 50-100 [millionths of a meter] to be filled, whereas pumping healing agents through a micro-vascular network can fill major cracks up to a millimeter across," Sottos said in a statement.
The researchers said they hope the technology can be used in civil engineering and construction applications.
“This set-up could be used with any microvascular network, including the structural composites reported on recently,” Sottos said in a press release. “In future materials, it would be ideal to have the pumping integrated in the materials itself.
“The advance of this paper is the study of active pumping/mixing for healing. We haven't applied this to healing with the structural composites yet; the present study was essential to understand what happens when we pump the healing agents.”
Image Caption: Vascular epoxy specimen containing two pairs of microchannels (280 microns in diameter) positioned to intersect cracks and release liquid healing agents into regions of damage. Each microchannel contains either a liquid resin (dyed red) or a liquid hardener (dyed blue), which react to form a polymer adhesive upon mixing. Inlets inserted into each microchannel enable connection of the microchannels to external pumps. Specimen height: is 40 mm.
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