Image of the Week - 01 September 2009

This SEM image shows the exposed surface of the fracture plane of a self-healing polymer. The hemispherical structures (one is magnified in the Inset, lower right) are microcapsules that had contained a healing agent before rupturing. Upon rupture, the healing agent spread via capillary action into the fracture, where it encountered catalyst that had also been embedded into the polymer matrix. The catalyst causes the healing agent to polymerize, thus repairing the crack. In this case the crack was opened to permit imaging of the fracture face.