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

Abstract 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.