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Nanofluidic transport for a blue energy

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The energy of mixing for instance between sea water and river fresh water appears as a major source of renewable energy that remains almost unused. Although the conversion principle to produce such a « blue energy » is known since the 70’s, the power density obtained up to know with ionic selective nanoporous membranes remains too low to be usable at an industrial scale. However new nanofluidic strategies are promising to improve this power density of several order of magnitudes. The conversion in itself relies on the coupling between convective, ionic and osmotic fluxes within a nanochannel with charged walls. Physical interactions, at the vicinity of the surface, are responsible for the coupling between these three transport mechanisms. Taking benefit of this coupling, conversion of power from one form to another (mechanical, electric, chemical) is possible when a thermodynamic potential gradient (pressure gradient, electric potential gradient, or chemical concentration gradient) is applied.

Mastering this blue energy, based on sensitive interfacial properties is a current challenge of nanofluidics both from a technological and academical point of view as fundamental questions are still in debate. This internship aims at improving the understanding of the coupling between hydrodynamics, electrical charges transport and chemical transport in order to be able to optimize energy conversion or recovery. For this purpose, we will take benefit of a novel experimental approach developed in our team to measure flow rate with an ultimate sensitivity simultaneously to electrical current and voltage.% to produce easily an individual well defined nanochannel within free standing membranes.
The student will consider first the case of a single calibrated conical nanochannel. We will focus on the impact of the geometry, especially the impact of dissymmetry of the channel on the flow rate and the emergence of possible flow rectification. In a second stage, we will consider the case of multiple pores and possible interactions between the pores that may lead to nonlinear effects. Finally the case of a flat nanochannel with large aspect ratio will be studied as a promising elementary brick of a futur high power density conversion system.

key words : nanofluidics, electrolytes, renewable energy, coupled transport, instrumentation

Contacts :
Elisabeth Charlaix, Cyril Picard