“This is a low-cost fabrication technique, and it resulted in the best optomechanical agreement between fluorescence and mechanical tests sensed by a nanocrystal in a film,” says Raja.

Raja says the tetrapods’ shape makes them very sensitive to stress. Their four arms act as antennae that take stress from their immediate environment, amplify the stress, and transfer it to the core. The color of light emitted by the core indicates the degree of stress (and strain) felt by the arms.

“This is the length scale at which cracks develop, which is when you want to catch them, well before the material fails,” says Shilpa Raja, who conducted the research while she was an affiliate in Berkeley Lab’s Materials Sciences Division and a PhD student at UC Berkeley. Raja is now a postdoctoral scholar at Stanford University. Robert Ritchie and Paul Alivisatos, also of the Materials Sciences Division and UC Berkeley, are the co-corresponding authors of a paper on this research published online in the journal Nano Letters (2016, vol. 16, issue 8, pgs. 5060-5067).

As always excellent find David!