"Contact Line Dynamics, Heat Transfer and Fluid Flow on Micro/Nanostructured Surfaces"

Speaker: Huihe Qiu, The Hong Kong University of Science & Technology, China

Micro/nanostructured surfaces makes the argument that optimum surfaces need to address the specificities of fluid flow and phase change heat transfer in the way that matches its multiscale textures and non-uniform wettability. It is possible to manipulate the nucleation site density, contact line dynamics, fluid flow, molecular diffusion/evaporation, local Marangoni forces and interplay of the interfacial free energies. In this talk, the questions of the effects of micro/nanostructured surfaces on the fluid flow, boiling, evaporation and freezing and the associated physical phenomena will be reviewed and addressed. We first report the bubble dynamics, fluid flow and heat transfer in a flow boiling microchannel with a chemically patterned microchannel surface. A significant challenge for the implementation of microscale flow boiling heat transfer is associated with micro/nanoflow instabilities due to insufficient micro/nano bubble removal, leading to local liquid dry-out which severely limits the heat removal efficiency. We will demonstrate experimentally how a chemically patterned surface can manipulate nucleation, fluid flow and heat transfer. Secondly, the contact line dynamics, fluid flow and species dynamics of an evaporating multicomponent droplet on chemically patterned surfaces will be reported utilizing a novel AIEgen-based direct visualization, high speed visualization, micro resolution PIV and ray tracing techniques. Utilizing the experimental and analytical results, the mechanisms behind contact line pinning/depinning and the critical receding contact angles under different species concentrations on chemically patterned surfaces are discussed in detail on the microscale. Finally, a recently developed nanostructured super-hydrophobic surface, inspired by the skin structure of a spring tail which can survive even in oil and ethenal1, structures with overhanging edge were provided recently and exhibited great wetting resistance ability, which may be used for anti-icing will be presented and discussed.