I Sense the Force

Abstract

Materials Science Although composite materials can show enhanced properties, understanding the way these materials deform and fail is not straightforward. Besides the individual properties of the matrix and the filler, one has to worry about the distribution of the filler particles, the strength of the interfacial bonding between the filler and matrix, and the way that the combined material will deform and debond. Raja et al. show that luminescent semiconductor nanocrystal tetrapods, composed of zinc-blend CdSe cores with epitaxially grown wurtzie CdS arms, can be used as stress sensors. The tetrapods were electrospun into a matrix of poly l-lactic acid at weight fractions ranging from 3.6 to 40%. During extension of the composite fibers, both the elastic and plastic deformation regions could be tracked through shifts in the fluorescence of the nanocrystals. The authors note that because the particles tend to clump and because there is incomplete stress transfer from the polymer to the nanocrystals, they do not deform plastically when the polymer does, thus giving greater reversibility to the stress measurements, as seen in comparing the fluorescence observations with traditional tensile measurements. Nano Lett. 10.1021/nl401999t (2013).