Tech Directions - February 2009 - (Page 11) technology today Alan Pierce pierceaj@optonline.net Self-Healing Materials finish. Both samples were scratched Your body has the ability to heal to break their protective coatings. itself. A small cut, scrape, or even a broken bone will immediately activate your body’s own healing processes. When you seek professional help for a serious injury, medical assistance is often limited to preventing infection, re-aligning broken bones, and cleaning wounds, so that conditions are right for the body to heal itself. The 20th-century materials that represent the backbone of our current technological world aren’t able to heal themselves. As a result, structures built with these materials have a limited lifespan before corrosion and other environmental defects necessitate repair or replacement. Material scientists and engineers Photo 1 are now learning how to create selfThese scratches were made equal in healing materials that can repair depth and width to guarantee that their own structures without human the only difference in the two samintervention. Recent press releases ples was their coatings. from university researchers describe The metal samples were then imthe development of a self-healing mersed in saltwater. When removed, protective finish and a self-healing corrosion was visible on the metal structural material. protected with the conventional rust Paul Braun and Scott White, proinhibitor. However, the surface of the fessors at the Beckman Institute at sample with the self-healing coating the University of Illinois, have recentdidn’t show any signs of corrosion. ly developed a self-healing coating The scientists used a scanning that prevents corrosion by healing electron microscope to focus in on breaks in the protective coating’s the scratched surfaces so that they surface. Braun sent me the photos and illustrations shown here to help me explain how the Braun and Scott self-healing finish breakthrough, without human intervention, repairs damages to its protective coating. Photo 1 shows two steel samples. The one on top was coated with a conventional rust inhibitor and the one on the bottom with their self-healing Fig. 1—Visual of how self-healing works could see the effectiveness of their self-healing finish. Photo 2 shows what the surfaces looked like at the microscopic level. The top image shows how corrosion has eaten into the conventionally protected metal. The bottom one shows that the original scratches have been filled in with a new coating that continues to protect the metal from corrosion. The drawings in Fig. 1 show what is going on at a nano scale. Figure 1a shows microcapsules encapsulated within the self-healing finish. When these capsules are broken (Fig. 1b), some microcapsules spill a polymer and others spill a catalyst. When these two ingredients mix (Fig. 1c) Photo 2 they react with each other creating a siloxane polymer caulking that fills in the scratches, thus sealing the scratches (Fig. 1d). I will explore self-healing structural materials in a future column. Recalling the Facts New technology often has positive and unforeseen negative effects. 1. Describe the positive effects of this technology. 2. What effect would this technology have on landfills when the products that contain these finishes are outdated? Alan Pierce, Ed.D., CSIT, is a technology education consultant. Visit www.technologytoday.us for past columns and teacher resources. www.techdirections.com TECHNOLOGY TODAY 11 Photos courtesy Paul Braun http://www.technologytoday.us http://www.techdirections.com
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