Chiral Optofluidics with a Plasmonic Metasurface Using the Photothermal Effect

Plasmonic metasurfaces with the photothermal effect have been increasingly investigated for optofluidics. Meanwhile, along with the expanding application of circularly polarized light, a growing number of investigations on chiral plasmonic metasurfaces have been conducted. However, few studies have explored the chirality and the thermal-induced convection of such systems simultaneously. This paper aims to theoretically investigate the dynamics of the thermally induced fluid convection of a chiral plasmonic metasurface. The proposed metasurface exhibits giant circular dichroism in absorption and thus leads to a strong photothermal effect. On the basis of the multiphysical analysis, including optics, thermodynamics, and hydrodynamics, we propose a concept of chiral spectroscopy termed optofluidic circular dichroism. Our results show that different fluid velocities of thermally induced convection appear around a chiral plasmonic metasurface under different circularly polarized excitation. The chiral fluid convection is induced by an asymmetric heat distribution generated by absorbed photons in the plasmonic heater. This concept can be potentially used to induce chiral fluid convection utilizing the chiral photothermal effect. Our proposed structure can potentially be used in various optofluidics applications related to biochemistry, clinical biology, and so on.