Asymmetric thermal optofluidics based on plasmonic multilayered nanostructures.

Manipulating thermo-convective fluid flow induced by plasmonic nanostructures under light illumination has garnered significant attention in various fields, such as biomedical sensing, particle trapping, and drug delivery. However, achieving symmetric optical manipulation of fluid flow encounters challenges in certain applications due to the inherent temporal and spatial symmetry in the energy transfer process. Here, a design of plasmonic nanostructures is proposed to achieve a platform for the asymmetric manipulation of thermally induced fluid flow in an optofluidic environment. The difference in fluid flow rate between forward and backward directions is due to the combined effect of the local asymmetry of the heat transfer in multilayer plasmonic nanostructure and nonreciprocity. The nonreciprocity originates from the violation of time-symmetry due to the temperature gradient-induced convection. We show that the asymmetric convective flow can also be achieved when the size of the plasmonic structure enlarges from nanometer to micrometer, and it can be used for efficient particle separation or transportation in microfluidic systems. Our findings expand the scope of optofluidic applications and stimulate the exploration of design approaches for optical devices. [ABSTRACT FROM AUTHOR]