Interaction confinement and electronic screening in two-dimensional nanofluidic channels

The transport of fluids at the nanoscale is fundamental to manifold biological and industrial processes, ranging from neurotransmission to ultrafiltration. Yet, it is only recently that well-controlled channels with cross-sections as small as a few molecular diameters became an experimental reality. When aqueous electrolytes are confined within such channels, the Coulomb interactions between the dissolved ions are reinforced due to dielectric contrast at the channel walls: we dub this effect `interaction confinement'. Yet, no systematic way of computing these confined interactions has been proposed beyond the limiting cases of perfectly metallic or perfectly insulating channel walls. Here, we introduce a new formalism, based on the so-called surface response functions, that expresses the effective Coulomb interactions within a two-dimensional channel in terms of the wall's electronic structure, described to any desired level of precision. We use it to demonstrate that in few-nanometer-wide channels, the ionic interactions can be tuned by the wall material's screening length. We illustrate this approach by implementing these interactions in brownian dynamics simulations of a strongly confined electrolyte, and show that the resulting ionic conduction can be adjusted between Ohm's law and a Wien effect behavior. Our results provide a quantitative approach to tuning nanoscale ion transport through the electronic properties of the channel wall material

Quantum feedback at the solid-liquid interface: flow-induced electronic current and negative friction

An electronic current driven through a conductor can induce a current in another conductor through the famous Coulomb drag effect. Similar phenomena have been reported at the interface between a moving fluid and a conductor, but their interpretation has remained elusive. Here, we develop a quantum-mechanical theory of the intertwined fluid and electronic flows, taking advantage of the non-equilibrium Keldysh framework. We predict that a globally neutral liquid can generate an electronic current in the solid wall along which it flows. This hydrodynamic Coulomb drag originates from both the Coulomb interactions between the liquid's charge fluctuations and the solid's charge carriers, and the liquid-electron interaction mediated by the solid's phonons. We derive explicitly the Coulomb drag current in terms of the solid's electronic and phononic properties, as well as the liquid's dielectric response, a result which quantitatively agrees with recent experiments at the liquid-graphene interface. Furthermore, we show that the current generation counteracts momentum transfer from the liquid to the solid, leading to a reduction of the hydrodynamic friction coefficient through a quantum feedback mechanism. Our results provide a roadmap for controlling nanoscale liquid flows at the quantum level, and suggest strategies for designing materials with low hydrodynamic friction

Exact numerical solution of the classical and quantum Heisenberg spin glass

We present the mean field solution of the quantum and classical Heisenberg spin glasses, using the combination of a high precision numerical solution of the Parisi full replica symmetry breaking equations and a continuous time Quantum Monte Carlo. We characterize the spin glass order and its low-energy excitations down to zero temperature. The Heisenberg spin glass has a rougher energy landscape than its Ising analogue, and exhibits a very slow temperature evolution of its dynamical properties. We extend our analysis to the doped, metallic Heisenberg spin glass, which displays an unexpectedly slow spin dynamics reflecting the proximity to the melting quantum critical point and its associated Sachdev-Ye-Kitaev Planckian dynamics

Collective modes and quantum effects in two-dimensional nanofluidic channels

Nanoscale fluid transport is typically pictured in terms of atomic-scale dynamics, as is natural in the real-space framework of molecular simulations. An alternative Fourier-space picture, that involves the collective charge fluctuation modes of both the liquid and the confining wall, has recently been successful at predicting new nanofluidic phenomena such as quantum friction and near-field heat transfer, that rely on the coupling of those fluctuations. Here, we study the charge fluctuation modes of a two-dimensional (planar) nanofluidic channel. Introducing confined response functions that generalize the notion of surface response function, we show that the channel walls exhibit coupled plasmon modes as soon as the confinement is comparable to the plasmon wavelength. Conversely, the water fluctuations remain remarkably bulk-like, with significant confinement effects arising only when the wall spacing is reduced to 7 Å. We apply the confined response formalism to predict the dependence of the solid–water quantum friction and thermal boundary conductance on channel width for model channel wall materials. Our results provide a general framework for Coulomb interactions of fluctuating matter under nanoscale confinement

Mapping outcomes of liquid marble collisions

© 2019 The Royal Society of Chemistry. Liquid marbles (LMs) have many promising roles in the ongoing development of microfluidics, microreactors, bioreactors, and unconventional computing. In many of these applications, the coalescence of two LMs is either required or actively discouraged, therefore it is important to study liquid marble collisions and establish parameters which enable the desired collision outcome. Recent reports on LM coalescence have focused on either two mobile LMs colliding, or an accelerating LM hitting a sessile LM with a backstop. A further possible scenario is the impact of a mobile LM against a non-supported static LM. This paper investigates such a collision, using high-speed videography for single-frame analysis. Multiple collisions were undertaken whilst varying the modified Weber number (We∗) and offset ratios (X∗). Parameter ranges of 1.0 0.25, and We∗ 1.55 resulted in 100% non-coalescence. Additionally, observations of LMs moving above a threshold velocity of 0.6 m s -1 have revealed a new and unusual deformation. Comparisons of the outcome of collisions whilst varying both the LM volume and the powder grain size have also been made, revealing a strong link. The results of this work provide a deeper understanding of LM coalescence, allowing improved control when designing future collision experiments

Effets à N corps dans le transport de fluides aux nanoéchelles

This thesis explores several phenomena that arise in nanoscale fluid transport due to inter-particle correlations. We show that in nanoscale channels, the walls affect not only the fluid motion, but also its interactions. As a result, we predict enhanced ionic correlations in confined electrolytes, with consequences ranging from ionic Cou- lomb blockade to memory effects. We further explore how correlations between interfacial water and electron dynamics in the channel wall result in a quantum contribution to hydrodynamic friction. Finally, we present the development of an experimental setup for measuring water flow through two-dimensional channels.Cette thèse explore plusieurs phénomènes de transport de fluides aux nanoéchelles qui résultent de corrélations entre les particules. Nous montrons que dans un canal nanométrique, les parois affectent non seulement le mouvement du fluide, mais aussi ses interactions. Ainsi, nous prédisons des corrélations ioniques renforcées dans les électrolytes confinés, avec des conséquences allant du blocage de Coulomb ionique aux effets de mémoire. Nous explorons ensuite les corrélations entre la dynamique de l’eau interfaciale et des électrons de la paroi solide, qui induisent une contribution quantique à la friction hydrodynamique. Enfin, nous présentons le développement d’un dispositif expérimental pour la mesure de flux d’eau dans des canaux bidimensionnels

Effets à N corps dans le transport de fluides aux nanoéchelles

This thesis explores several phenomena that arise in nanoscale fluid transport due to inter-particle correlations. We show that in nanoscale channels, the walls affect not only the fluid motion, but also its interactions. As a result, we predict enhanced ionic correlations in confined electrolytes, with consequences ranging from ionic Coulomb blockade to memory effects. We further explore how correlations between interfacial water and electron dynamics in the channel wall result in a quantum contribution to hydrodynamic friction. Finally, we present the development of an experimental setup for measuring water flow through two-dimensional channels.Cette thèse explore plusieurs phénomènes de transport de fluides aux nanoéchelles qui résultent de corrélations entre les particules. Nous montrons que dans un canal nanométrique, les parois affectent non seulement le mouvement du fluide, mais aussi ses interactions. Ainsi, nous prédisons des corrélations ioniques renforcées dans les électrolytes confinés, avec des conséquences allant du blocage de Coulomb ionique aux effets de mémoire. Nous explorons ensuite les corrélations entre la dynamique de l’eau interfaciale et des électrons de la paroi solide, qui induisent une contribution quantique à la friction hydrodynamique. Enfin, nous présentons le développement d’un dispositif expérimental pour la mesure de flux d’eau dans des canaux bidimensionnels

Many-body effects in nanoscale fluid transport

Cette thèse explore plusieurs phénomènes de transport de fluides aux nanoéchelles qui résultent de corrélations entre les particules. Nous montrons que dans un canal nanométrique, les parois affectent non seulement le mouvement du fluide, mais aussi ses interactions. Ainsi, nous prédisons des corrélations ioniques renforcées dans les électrolytes confinés, avec des conséquences allant du blocage de Coulomb ionique aux effets de mémoire. Nous explorons ensuite les corrélations entre la dynamique de l’eau interfaciale et des électrons de la paroi solide, qui induisent une contribution quantique à la friction hydrodynamique. Enfin, nous présentons le développement d’un dispositif expérimental pour la mesure de flux d’eau dans des canaux bidimensionnels.This thesis explores several phenomena that arise in nanoscale fluid transport due to inter-particle correlations. We show that in nanoscale channels, the walls affect not only the fluid motion, but also its interactions. As a result, we predict enhanced ionic correlations in confined electrolytes, with consequences ranging from ionic Coulomb blockade to memory effects. We further explore how correlations between interfacial water and electron dynamics in the channel wall result in a quantum contribution to hydrodynamic friction. Finally, we present the development of an experimental setup for measuring water flow through two-dimensional channels