Lydéric Bocquet

Directeur de Recherche CNRS,
Professeur Attaché à l'Ecole Normale Supérieure
Membre de l'Académie des sciences

Laboratoire de Physique,
Ecole Normale Supérieure, Paris

Vidéo de la leçon inauguraleau Collège de France: 'The molecular mechanics of fluids'

"Là où j'ai peur, j'irai", Anne Sylvestre

My research

My research is at the interface between condensed matter, fluid dynamics and nano-science. It is mostly curiosity driven. We combine experiments, theory, and molecular simulations to explore the intimate mechanisms of the dynamics of fluid interfaces from the macroscopic down to the molecular level.
My main line of research over the past ten years has been nanofluidics, the science of molecular flows. This world of the infinitely small in fluidics is the frontier where the continuum of fluid mechanics meets the atomic or even quantum nature of matter. In the team, we have developed unique experiments to study fluid transport in individual nanochannels, demonstrating giant osmotic transport in boron-nitrogen nanotubes, ultra-fast flows in carbon nanotubes - highlighting quantum friction effects -, or the demonstration of neuromorphic effects in two-dimensional systems.
Nanofluidics is also a field where the path from fundamental science to breakthrough innovation is short, notably for desalination, water remediation or osmotic energy. My fundamental research has led to the creation of four start-ups, including Sweetch Energy in the field of osmotic energy and Hummink in the field of additive manufacturing on a nanometric scale.

Read a general perspective on nanofluidics in this Pour La Science article (in french)

Research interests

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    Nanofluidics : fluid transport in individual nanotubes, blue energy, ionic machines

    New paradigms for fluid transport are expected to emerge from the confinement of liquids at the nanoscales, which is the domain of nanofluidics, with potential breakthroughs in ultrafiltration, desalination, and energy harvesting. Nevertheless, advancing the fundamental understanding of fluid transport at the smallest scales requires mass and ion dynamics to be ultimately characterized across an individual channel so to avoid averaging over many pores. To this aim, we have developped various nanofluidic plateforms using nanomanipulation methods, and allowing to investigate the properties of individual nanotubes. Among results, we have demonstrated giant osmotic energy conversion in BNNT nanotubes, as well as a diameter dependent giant slippage in carbon nanotubes. We now explore active nanofluidics, with the aim to boost and control transport at the ultimate scales, in the quest to design ionic machines.
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    Fluid dynamics at interfaces

    We have explored how interfaces modify the statics and dynamics of liquids, both theoretically and experimentally. We have studied Liquid-solid friction and the question of hydrodynamic slippage at the molecular scales, on bare and super-hydrophobic surfaces. Thanks to Tuning Fork AFM, we have evidenced a capillary freezing of ionic liquids in the presence of metallic surfaces, pointing to the role of electronic screening effects in Soft Matter.
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    From nano to macro

    Opposite to the exploration of smaller and smaller length scales in fluids, we have followed a reverse, bottom-up approach for fluid dynamics: may one impact macroscopic flows via nanometric details, coupling the small and the large ? While such effects are not a priori expected due to a huge difference in energy scales, we have demonstrated in several situations that such a link was indeed possible, eg during the impact of a solid body on a liquid surface (splash or plop), as well as for flow separation on solid surfaces, usually coined as the teapot effect. In both cases, we shown that microdetails lead to macro-consequences, the summum being obtained with super-hydrophobic surfaces.
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    Colloidal transport and active colloidal suspensions

    We have explored various aspects of colloidal transport, and in particular the so-called diffusio-phoresis, i.e. motion of particles under solute (salt) gradients. Using the microfluidics technology, we have shown that this phenomenon, which bares some analogy with chemotaxis of biological entities, allows to harvest the chemical energy contained in solute contrasts to induce a strong migration of the particles. Beyond, we used this phenomenon to power chemically-driven active colloids, which self-propel using a chemical reaction at their surface. Most recently, we explored the behavior of magnetotactic bacteria which exhibit unexpected spatial patterns under flow. This opens the possibility to explore the phase behavior of active colloidal suspension, which exhibits new behaviors and phases.
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    Soft Glassy flows

    We explore the flow behavior of soft glassy materials, such as emulsions, gels,... which behave like solids at rest and flow under a sufficiently applied stress. We have demonstrated the existence of non-local/cooperativity effects in the rheology, a behavior which is accounted for by a non-local fluidity description, and justified on the basis of a mesoscopic Kinetic Elasto-Plastic (KEP) model that we developped. This phenomenology allows to rationalize most behaviors of such materials. Recently we extended our interest to shear-thickening systems, showing how the nanoscale pairwise frictional properties between individual beads determinate the macroscopic shear-thickening behavior.
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    Physics of everyday life

    I have a high interest and strong implication in physics of everyday life. Examples are physics of stone-skipping, splashes, physics in the kitchen (ironing, cooking of potatoes, teapot effect, ...), based on fundamental physics applied to problems encountered in our everyday life. We are currently exploring the role of waxing on ski friction, in collaboration with the french biathlon team.

Recent articles

Article n189

«Fluctuation-induced quantum friction in nanoscale water flows»
Nature (2022)

Article n186

« “Modeling of emergent memory and voltage spiking in ionic transport through angström-scale slits”» Science (2021)

Article n169

«Molecular streaming and its voltage control in ångström-scale channels» Nature (2019)