Color-changing indicators highlight microscopic damage

Nature Reviews: Materials (Feb. 1) -- Cracks in polymer coatings and composites can lead to faster degradation of the underlying substrates or a reduction in the mechanical performance of the composite over time. In the case of polymer-coated steel structures -- for example, ships and bridges -- the detection of cracks at an early stage is essential to prevent corrosion, particularly in marine settings. Materials science and engineering professor Nancy Sottos and her colleagues at Illinois show the visual detection of mechanical damage in epoxy polymer coatings using microcapsules containing a chemical indicator.