RESUMO
This research demonstrates that a surface plasmon resonance (SPR) imaging technique can effectively measure full-field nanoscale thickness of a liquid water film filled in the receding contact-induced nano-channel. To the authors' knowledge this has not been demonstrated previously. Experimental calibration has been conducted by measuring surface plasmon resonance reflectance depending on the piezometer-controlled water nano-film thickness and comparing the experimental results with the theoretical calculations to show very good agreement. The measured full-field thickness profiles significantly visualize the three-dimensional nano-channel formation filled with liquid water film. It shows that the sensitivity and the resolution in thickness measurement are estimated as 1.21 pixel gray level/nm and 2.5 nm, respectively. The experimentally observed resolution is around 10 nm given the uncertainty in the demonstrated full-field mapping of thickness. From this research, it is demonstrated that SPR imaging successfully measures the thickness of ultrathin liquid film especially below 85 nm in full-field under normal conditions and can effectively characterize the three-dimensional nano-channel formation during the receding contact process.
RESUMO
Nanophotonic technique has been attracting much attention in applications of nano-bio-chemical sensing and energy conversion of solar energy harvesting and enhanced energy transfer. One approach for nano-bio-chemical sensing is surface plasmon resonance (SPR) imaging, which can detect the material properties, such as density, ion concentration, temperature, and effective refractive index in high sensitivity, label-free, and real-time under ambient conditions. Recent study shows that SPR can successfully detect the concentration variation of nanofluids during evaporation-induced self-assembly process. Spoof surface plasmon resonance based on multilayer metallo-dielectric hyperbolic metamaterials demonstrate SPR dispersion control, which can be combined with SPR imaging, to characterize high refractive index materials because of its exotic optical properties. Furthermore, nano-biophotonics could enable innovative energy conversion such as the increase of absorption and emission efficiency and the perfect absorption. Localized SPR using metal nanoparticles show highly enhanced absorption in solar energy harvesting. Three-dimensional hyperbolic metamaterial cavity nanostructure shows enhanced spontaneous emission. Recently ultrathin film perfect absorber is demonstrated with the film thickness is as low as ~1/50th of the operating wavelength using epsilon-near-zero (ENZ) phenomena at the wavelength close to SPR. It is expected to provide a breakthrough in sensing and energy conversion applications using the exotic optical properties based on the nanophotonic technique.