Fast and Versatile Thermo-osmotic Flows with a Pinch of Salt

Cecilia Herrero (1) , Michael de San Feliciano (1) , Samy Merabia (1) , Laurent Joly (1, 2)

1 iLM - MMCI - iLM - Modélisation de la matière condensée et des interfaces
2 IUF - Institut universitaire de France

Thermo-osmotic flows – flows generated in micro and nanofluidic systems by thermal gradients – could provide an alternative approach to harvest waste heat. However, such use would require massive thermo-osmotic flows, which are up to now only predicted for special and expensive materials. Thus, there is an urgent need to design affordable nanofluidic systems displaying large thermo-osmotic coefficients. In this paper, we propose a general model for thermo-osmosis of aqueous electrolytes in charged nanofluidic channels, taking into account hydrodynamic slip, together with the different solvent and solute contributions to the thermo-osmotic response. We apply this model to a wide range of systems by studying the effects of wetting, salt type and concentration, and surface charge. We show that intense thermo-osmotic flows can be generated using slipping charged surfaces. We also predict for intermediate wettings a transition from a thermophobic to a thermophilic behavior depending on the surface charge and salt concentration. Overall, this theoretical framework opens an avenue for controlling and manipulating thermally induced flows with common charged surfaces and a pinch of salt.

Domaines: Mécanique des fluides [physics.class-ph]; Matière Molle [cond-mat.soft]

Cecilia Herrero, Michael de San Feliciano, Samy Merabia, Laurent Joly. Fast and Versatile Thermo-osmotic Flows with a Pinch of Salt. Nanoscale, 2022, 14 (3), pp.626-631. ⟨10.1039/D1NR06998E⟩. ⟨hal-03404802v2⟩