Dense Brushes of Tilted Metallic Nanorods Grown onto Stretchable Substrates for Optical Strain Sensing

This study aims to investigate the potential of small densely packed tilted Au nanorods grown on a flexible substrate by physical vapor deposition for strain sensing. By exciting the rods with linearly polarized white light that is perpendicularly impinging onto the sample substrate, interesting plasmonic properties emerge. Electron microscopy characterization shows that the rods are grown at a shallow angle relative to the substrate, as expected for glancing angle deposition conditions. Due to their nonorthogonal orientation, specific coupled multirod plasmon modes are detected for both longitudinal and transverse illumination under illumination normal to the substrate. In a second step, we have performed in situ mechanical tests and showed higher sensitivity to the applied strain for longitudinal E-field directions, which are more strongly affected by changes in inter-rod gaps than for transverse illumination. What is remarkable is that, despite the inherent disorder to this self-assembled system, clear features like polarization dependency and localized surface plasmon resonance (LSPR) wavelength shift with applied strains may be observed due to local changes in the nanorods’ environment. These nanorod coated flexible substrates rank among the most sensitive plasmonic strain sensors in the literature and have potential to be embedded in real strain sensing devices.