Molecular views on thermo-osmotic flows

Transcription

1 Molecular views on thermo-osmotic flows Li Fu, Samy Merabia, Laurent Joly Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622, Villeurbanne, France

2 Nanofluidics with LAMMPS 2 Micro/nanofluidic transport: from molecular mechanisms to applications Interfacial hydrodynamics Liquid/solid friction Understanding water Energy conversion Electrokinetic effects! " #!! "! $!! " #! #!! " #!! " #! Nanoscale flows Figure 2: initial configuration of System 2 with [MMIM + ] in bright red and [NTF2 - ] in blue Lubrication Devices Two crystallographic configurations of CuO were simulated; the first corresponded to CuO, forming layers of copper and oxygen perpendicular to the XY plane (System 1), see Figure 3. The second configuration corresponded to CuO forming layers of copper and oxygen parallel to the XY plane (System 2), Figure System Interactions

3 Nanofluidics with LAMMPS 3 Micro/nanofluidic transport: from molecular mechanisms to applications Interfacial hydrodynamics Liquid/solid friction Understanding water Energy conversion Electrokinetic effects! " #!! "! $!! " #! #!! " #!! " #! Nanoscale flows Figure 2: initial configuration of System 2 with [MMIM + ] in bright red and [NTF2 - ] in blue Lubrication Devices Two crystallographic configurations of CuO were simulated; the first corresponded to CuO, forming layers of copper and oxygen perpendicular to the XY plane (System 1), see Figure 3. The second configuration corresponded to CuO forming layers of copper and oxygen parallel to the XY plane (System 2), Figure System Interactions

4 Osmotic flows 4 Surface-driven flows generated by non-hydrodynamic forcing Electro-osmosis Diffusio-osmosis Thermo-osmosis charge excess solute excess enthalpy excess Micro/nanofluidics, sustainable energies (e.g. waste heat harvesting) Originate in a nanometric interfacial layer Nanoscale structure and dynamics

5 Osmotic flows 5 Surface-driven flows generated by non-hydrodynamic forcing Electro-osmosis Diffusio-osmosis Thermo-osmosis charge excess solute excess enthalpy excess Micro/nanofluidics, sustainable energies (e.g. waste heat harvesting) Originate in a nanometric interfacial layer Nanoscale structure and dynamics

6 Nanofluidic systems under thermal gradients 6 For applications Zambrano et al. Nano Lett 2009 Zhao & Wu Nano Lett 2015 Gupta & Jiang ChemistrySelect 2017 Molecular mechanisms? Oyarzua, Walther & Zambrano, PCCP 2018 Ganti, Liu & Frenkel, PRL 2017 Effect of wetting and interfacial hydrodynamics?

7 Theory 7 Thermo-osmosis flow induced by a thermal gradient: Mechano-caloric effect heat flux induced by a pressure gradient: Standard prediction: Interfacial hydrodynamics: stagnant layer (z s ), slip (b) Derjaguin and Sidorenkov, 1941 enthalpy density excess Following analogous treatment of electro-osmosis by Huang et al. Fu, Merabia, Joly, PRL 2017

8 Molecular dynamics 8 Generic Lennard-Jones interaction potential: Effect of wetting? Varying liquid-solid interaction energy e ls Fu, Merabia, Joly, PRL 2017

9 Molecular dynamics 9 Measurements Theoretical prediction from # of particles in reservoirs from temperature profile in channel hydrodynamics: from Poiseuille flow in mechano-caloric configuration thermodynamics: from equilibrium simulations Fu, Merabia, Joly, PRL 2017

10 Molecular dynamics 10 Measurements Theoretical prediction from # of particles in reservoirs from temperature profile in channel hydrodynamics: from Poiseuille flow in mechano-caloric configuration thermodynamics: from equilibrium simulations Fu, Merabia, Joly, PRL 2017 compute stress/atom:

11 Results 11 Thermo-osmotic route viscous entrance effects Wetting systems cf. experiments ~ to 10-9 m 2 /s change of sign cf. Lüsebrink, Yang, Ripoll, JPCM 2012 non-wetting Fu, Merabia, Joly, PRL 2017 wetting Non-wetting systems giant response up to

12 Interfacial hydrodynamics 12 Wetting systems Oscillations of the excess enthalpy crucial role of z s Non-wetting systems Molecular thickness of the interaction layer large amplification by slip Fu, Merabia, Joly, PRL 2017 cf. electro-osmosis: Joly et al. PRL 2004, JCP 2006 Joly et al. PRL 2014, Barbosa De Lima & Joly 2017 diffusio-osmosis: Ajdari & Bocquet, PRL 2006 thermo-phoresis: Morthomas, Würger, JPCM 2009

13 Water-graphene interface 13 Giant thermo-osmotic response: Waste heat harvesting with graphitic membranes? entrance pressure drop thermal short-circuit by walls desalination applications: ultra-confinement Fu, Merabia, Joly, PRL 2017

14 Carbon nanotube membranes 14 Analytical model coupling thermodynamics and hydrodynamics MD simulations Fu, Merabia, Joly, J. Phys. Chem. Lett. 2018

15 Carbon nanotube membranes 15 Pumping (DP = 0) Desalination / overcoming a pressure difference cf. Dariel & Kedem J. Phys. Chem Model validated by MD results -> can help searching for other innovative membranes Fast and robust flows (even when extrapolated to experimental parameters) Fu, Merabia, Joly, J. Phys. Chem. Lett. 2018

16 Conclusion 16 Osmotic flows generated in the nanometric vicinity of interfaces Molecular structure and dynamics Interfacial hydrodynamics can control amplitude and sign of the response! Molecular dynamics simulations However: Numerical investigations limited to classical molecular dynamics reactivity? see e.g. Joly et al., J. Phys. Chem. Lett NECtAR project: Nanofluidic Energy Conversion using reactive surfaces Bonhomme, Blanc, Joly, Ybert, Biance, Adv. Colloid Interface Sci Hartkamp, Biance, Fu, Dufrêche, Bonhomme, Joly, submitted to Curr. Opin. Colloid Interface Sci

17 Thank you 17 Li Fu Samy Merabia French National Research Agency, project NECtAR Institut Universitaire de France Joly, Detcheverry, Biance, PRL 2014 Barbosa De Lima, Joly, Soft Matter 2017 Lee, Cottin-Bizonne, Fulcrand, Joly, Ybert, J. Phys. Chem. Lett Fu, Merabia, Joly, PRL 2017 Fu, Merabia, Joly, J. Phys. Chem. Lett

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19 Thermo-osmosis: waste heat 19 Heat management: a crucial challenge Waste heat produced by industry and energy conversion Large fraction of low grade waste heat Energy loss through waste heat (Penn State University) Distribution of waste heat in industry Could nanofluidic systems be used for (low grade) waste heat harvesting?

20 Interfacial hydrodynamics 20 Hydrodynamic slip Slip length b ~ tens of nm Flow amplification factor: 1 + b L interfacial layer thickness Electro-osmosis Diffusio-osmosis l D Joly et al., PRL 2004, JCP 2006 Joly et al., PRL 2014 Barbosa De Lima & Joly 2017 Ajdari & Bocquet, PRL 2006

21 A more general model 21 Continuum hydrodynamics (cst h), partial slip BC with Stokes equation Partial slip BC at z = z w z x e = bulk permittivity, no assumption on e(z) close to the surface Uncharged surfaces: independent of b (i.e. of friction) Huang et al., PRL 2007, Langmuir 2008

22 Model (1) 22 Thermal gradient thermodynamic force density with Fluid friction on the wall: Bare thermo-osmotic velocity in the tube (large slip limit) with General hydrodynamic boundary condition with

23 Model (2) 23 Backflow due to: viscous entrance pressure drop pressure difference between reservoirs Sampson, 1891 Total velocity through the membrane (large slip limit) General hydrodynamic boundary condition cf. Dariel & Kedem J. Phys. Chem. 1975

24 Molecular dynamics 24 Model (DP = 0): Quantitative match between model and MD results Crucial role of hydrodynamics The MD-validated model can predict velocity in experimental situations Giant velocities, despite entrance effects and thermal short-circuit mechanism Reaching a plateau ~ 0.5 m/s for large radii Complex dependency on R for small radii

25 Enthalpy profiles 25 Model (DP = 0): Weak confinement: model predicts constant velocity Strong confinement: overlap of the interaction layers complex evolution of

26 Overcoming a pressure difference 26 Desalination possible! MD simulation with (model: )