Flexible thermo-plasmonics: an opto-mechanical control of the heat generated at the nanoscale

The opto-mechanical control of the heat generated by an amorphous arrangement of homogenously distributed gold nanoparticles (AuNPs), excited by an external laser source, is investigated. Application of a macroscopic mechanical strain to the biocompatible elastomeric tape supporting the particles leads to a nanoscale modification of their mutual inter-distance. The resulting strong variation of the particles near-field coupling gives rise to a macroscopic variation of the photo-generated heat. A fine control of the amount of generated heat is thus possible by stretching the initially isotropic sample by only a few percent. Due to the anisotropy of the stretching procedure, the plasmon band shift and thus the heat generation becomes strongly polarization-dependent. A model of the system based on Mie theory is implemented by using a finite element method. Under optical excitation, two configurations of AuNPs, representing the same cluster of particles at rest and under stretching, show a relative increase of temperature that is in good quantitative agreement with experimental data, if normalized to the number of involved particles. This system realizes for the first time an opto-mechanical control of the temperature at the nanoscale which holds promise for the development of optically-active thermal patches, usable for biomedical applications, and flexible platforms for microfluidics and lab-on-a-chip devices.