Fast and versatile thermo-osmotic flows with a pinch of salt

Abstract

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...

Chapter: Energy conversion at water-solid interfaces using electrokinetic effects

“…It is interesting to note that, while 𝑀 el to is always negative, the water contribution can change sign for different water-substrate interactions, or more specifically wetting properties [68]. Therefore, for a given salt, there can be a competition between water and electrostatic contributions, and the flow can exhibit (or not) a change of sign with 𝑥 depending on the amplitude of Σ.…”

“…where, analogously to the thermo-osmotic response situation, one can consider that the main contributions to 𝛿ℎ(𝑧) are the same as discussed in Sec. 3.4 [111,68]. We can compute the classical electrostatic contribution to the thermoelectric response in the slip situation.…”

Thermo-osmotic flow in slit channels with boundary slip: giant flow amplification between polarized graphene surfaces

“…Similar approaches were used to compute the thermo-osmotic flow (TOF) in channels with polyelectrolytes attached to the channel walls (Maheedhara et al 2018;Sivasankar et al 2021), the influence of thermo-osmosis on the Seebeck coefficient (Zhang et al 2019) and the influences of channel entrance effects and the thermal conductivity of the channel walls (Zhang et al 2022). Recently, by employing molecular dynamics (MD) simulations, it was shown that not only the temperature-induced modifications of the EDL structure can drive thermo-osmosis, but also the modifications of the liquid enthalpy close to the solid surface due to ion solvation and water dipole orientation (Fu, Merabia & Joly 2017;Herrero et al 2022).…”

Fluid flow at interfaces driven by thermal gradients

“…This approach was proposed many years ago by Derjaguin [15][16][17] and identifies the driving force as the local enthalpy change induced by the confining surface. At the moment, most of the numerical and experimental works on thermo-osmosis in liquids essentially rely on this theory for the interpretation of their results [20,[26][27][28]. In particular, in molecular dynamics simulations the velocity profile is obtained by evaluating the excess enthalphy near the wall, which acts as the force term in the linearized Navier-Stokes equations.…”

“…However, the hypothesis underlying continuum theories is that the relevant observables vary on a length scale much larger than the typical range of the interaction: Near a surface this condition is no longer satisfied because the fluid properties eventually driving the phenomenon may display strong, but short ranged, modulations. In addition, the viscosity, which is assumed to be constant in the whole system [16,[26][27][28], is perturbed near the the interface. Therefore, it is not surprising that the classical macroscopic paradigm can fail to predict even the direction of the induced flows.…”