Plasmonic Based Microcapsules as Strain Sensors

Plasmonic nanoparticles (NPs) assembled into two- or three-dimensional architectures offer new collective optical properties. Indeed, closely packed gold nanoparticles (Au NPs) absorb light at higher wavelength than when they are far apart. Au NPs were assembled onto droplets to fabricate new dispersed materials. By tuning the charges and wettability of Au NPs, they adsorb and pack at the surface of emulsion droplets. A subsequent silanization at the interface of the emulsion allows to lock the NPs inside a silica shell. Au NP-silica microcapsules are obtained by that process. The Au NP-silica microcapsules were inserted in a polymeric film. When the films are stretched, the microcapsules are deformed into elongated ellipsoidal shapes and the distance between the Au NPs embedded in their shells concomitantly increases. As the extinction of Au NPs depends on the separation between the Au NPs, the microcapsules exhibit different colors when they are deformed. These novel microcapsules can be used to detect and measure mechanical deformations by outputting a color change. Each one of the microcapsules being one sensor by itself, these results pave the way as for the design of new microscale sensors.