Nanopillars have been shown to mechanically damage bacteria, suggesting a promising strategy for future antibacterial surfaces. However, the mechanisms underlying this phenomena remain unclear, which ultimately limits translational potential toward real-world applications. Using real-time and end-point analysis techniques, we demonstrate that in contrast to initial expectations, bacteria on multiple hydrophilic “mechano-bactericidal” surfaces remained viable unless exposed to a moving air–liquid interface, which caused considerable cell death. Reasoning that normal forces arising from surface tension may underlie this mechano-bactericidal activity, we developed computational and experimental models to estimate, manipulate, and recreate the impact of these forces. Our experiments together demonstrate that a critical level of external force acting on cells attached to nanopillar surfaces can rapidly deform and rupture bacteria. These studies provide fundamental physical insight into how nanopillar surfaces can serve as effective antibacterial materials and suggest use-conditions under which such nanotechnology approaches may provide practical value.

Metal nanoparticles have the ability to strongly enhance the local electromagnetic field in their vicinity. Such enhancement is crucial for biomolecular detection and is used by techniques such as surface plasmon resonance detection or surface-enhanced Raman scattering. For these processes, the sensitivity strongly depends on the electromagnetic field intensity confined around such nanoparticles. In this article, we have numerically studied an array of metallic nanocylinders, which can sustain localized surface plasmons (LSP). However, the excitation wavelengths of the LSP are not tunable due to their limited dispersion. We have demonstrated a plasmonic mode, the hybrid lattice plasmon (HLP), which is excited in such a periodic array by adding a uniform thin metallic film below it. This mode is a result of a harmonic coupling of the propagating surface plasmons present in such a metallic film with the Bragg waves of the array. It shows a strong confinement of the electromagnetic field intensity around the nanocylinders, similar to the LSP, but the dispersion of this HLP mode is, however, similar to that of the propagating plasmons and, thus, can be tuned over a wide range of excitation wavelengths. The structure was fabricated using electron beam lithography and characterized by a surface plasmon resonance setup. These experimental results show that the HLP mode can be excited in a classical Kretschmann configuration with a dispersion similar to the prediction of numerical simulations.

Directional plasmon excitation and surface enhanced Raman scattering (SERS) emission were demonstrated for 1D and 2D gold nanostructure arrays deposited on a flat gold layer. The extinction spectrum of both arrays exhibits intense resonance bands that are redshifted when the incident angle is increased. Systematic extinction analysis of different grating periods revealed that this band can be assigned to a propagated surface plasmon of the flat gold surface that fulfills the Bragg condition of the arrays (Bragg mode). Directional SERS measurements demonstrated that the SERS intensity can be improved by one order of magnitude when the Bragg mode positions are matched with either the excitation or the Raman wavelengths. Hybridized numerical calculations with the finite element method and Fourier modal method also proved the presence of the Bragg mode plasmon and illustrated that the enhanced electric field of the Bragg mode is particularly localized on the nanostructures regardless of their size.