Nano- to Mm-Scale Fluid Dynamic Phenomena Induced by Plasmon-Assisted Photothermal Effect in Microfluidic Channels

Photothermal effect induced by plasmonic nanostructures has been widely used for fluid manipulation and heat transport in lab-on-a-chip applications based on microfluidics. In this article, a comprehensive multiscale and multiparameter study is presented for a 3D gold nanoparticles (AuNPs) based optofluidic channel. Multiphysics simulations using finite element method (FEM), consisting of electromagnetic, thermal, and fluid flow fields are used to analyze both steady-state spatial distribution and transient evolutions of the thermally driven fluid dynamic phenomena in the microscopic field. This study demonstrates that a nano-scale thermal gradient can lead to nm-scale changes in fluid dynamics and on the nano-scale, while such convection does not significantly affect the steady-state temperature distribution, even in the presence of injection flow, but the localized thermal-driven convection will contribute to the flow dynamics to some extent. Given the millimetric size of the heat source in microfluidic system, convection exerts a powerful influence to control fluid motion and temperature gradient. Moreover, thanks to a comprehensive parameter study involving AuNPs temperature, channel height, and injection flow velocity, this work elucidates the role of pressure-driven flow and thermal-induced convection in controlling fluid and mass transport in microfluidic conditions, which will enhance the functionality of plasmofluidics for various bioapplications.