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Frédéric Restagno

MMOI Group leader

CNRS Chargé de recherche (CNRS Research Associate Professor)
Habilitation à diriger les recherches
Bât. 510 - Campus d’Orsay
91405 Orsay Cedex
Tél. : +33 (0)1 69 15 56 45
Fax : +33 (0)1 69 15 60 86
Mail :


ResearcherID: G-6460-2011
ScopudID: 55935913700
Frédéric Restagno on researchgate

Other activities

- Soft matter and biological physics (ex. Macroscopical physics and complexity, ex. Physique des liquides) director - Physique macroscopique et complexité
- iCFP representative for Université Paris-Saclay
- Jury de l’agrégation de sciences physique - option physique
- ANR Encore Scientific coordinator
- Member of the National organization committee of the french "Olympiades de physiques"
- Nominated member of the scientific council of the Physics Department of the Université Denis Diderot.
- Member of the Société Française de Physique, Société Française de l’Adhésion, American Adhesion Society, American Physical Society, American Chemical Society.

Research interest

- Polymer physics
- Adhesion
- Friction
- Lubrication and nanorheology
- Textured materials
- Wetting

Science popularization

- I have participated to 9 "On n’est pas que des cobayes" (France 5/2P2L) TV shows. [watch]
- I participated to 2 stop-motion movies: "Un chercheur et son article" and "Chercheur et caféine" with C. Arène and J. Bobroff.
- I gave several seminars for broad audiences. This first one with A. Chateauminois is [link] on friction phenomenon, this other one with E. Rio [link] is related to bubbles, drops and liquid interfaces.
- I participated to the E=M6 TV show [link].

Present PhD students

- Marceau Hénot (since sept. 2015) - Co-advised with L. Léger
- Marion Grelzka (since sept. 2016) - Co-advised with L. Léger
- M. Mantelet (since sept. 2016) - Co-advised with I. Souchon and V. Mathieu at INRA

Former PhD students

New: Thesis available on

- Céline Cohen (co-advised with L. Léger) [webpage]
- Laurie Saulnier (co-advised with E. Rio and D. Langevin) [LinkedIn]
- Emmanuelle Martinot [LinkedIn]
- Alexis Chennevière (now researcher at the CEA - LLB laboratory)
- Lorène Champougny (co-advised with E. Rio and B. Scheid)
- Laetitia Dies-Diverchy (co-advised with C. Poulard)[LinkedIn]
- Stéphanie Vuong (co-advised with L. Léger) [LinkedIn]

Popular science articles

  • Lorenceau, É., Reyssat, É., Restagno, F. & Quéré, D. Pointes liquides. Reflets de la physique 15–18 (2007). doi:10.1051/refdp/2007034 [pdf]
  • Charlaix, É. et al. Propriétés hydrodynamiques au voisinage d’une surface. Reflets de la Physique 14–18 (2010). [pdf]
  • Villey, R., Cottin-Bizonne, C., Léger, L., Charlaix, É. & Restagno, F. Indenter du verre avec un liquide? Reflets de la physique 38–40 (2015). [pdf]
  • Dalnoki-Veress, K., Salez, T. & Restagno, F. Why can’t you separate interleaved books? Physics Today 69, 74–75 (2016). [pdf]
  • Restagno, F. Les empreintes digitales augmentent-elles l’adhérence ? Pour la science 389, (2010). [pdf]


  • H. Alarcón, T. Salez, C. Poulard, J. - F. Bloch, É. Raphaël, K. Dalnoki-Veress, and F. Restagno, “Self-Amplification of Solid Friction in Interleaved Assemblies”, Physical review letters, vol. 116, no. 1, p. 015502, 2016.

  • N. Amouroux, F. Restagno, and L. Leger, “Adhesion at poly(butylacrylate)-poly(dimethylsiloxane) interfaces”, JOURNAL OF ADHESION, vol. 83, no. 8, p. 741-760, 2007.
    Abstract: We present an investigation of the adhesion modulation mechanisms of silica-like nanoparticles (MQ resins) incorporated in polydimethylsiloxane ( PDMS) elastomers and acrylic adhesives. The Johnson-Kendall-Roberts (JKR) test has been used to gain information on the both zero velocity and the velocity dependence of the adhesive strength, avoiding as much as possible contributions to the adhesive strength of bulk dissipation in the adhesive ( which is not the case with peel tests). As the incorporation of the MQ resins into the elastomers deeply affects their own mechanical properties, the loading and unloading curves of small poly(butylacrylate) (PBA) lenses on either PDMS elastomers, adsorbed PDMS and pure MQ resin layers are compared in a systematic manner. The PBA chains are observed to have a neat affinity for the MQ resin nanoparticles. When MQ resins are present at the interface, they tend to prevent facture propagation, thus producing a larger deformation of the PBA lens. The modulation of adhesion is then dominated by the corresponding dissipation inside the acrylic adhesive.
    Tags: acrylic adhesives, adhesion mechanisms, dissipation, interfacial interactions, JKR test, modulation of adhesion, silicone elastomers.

  • T. Barraud, F. Restagno, S. Devisme, C. Creton, and L. Leger, “Formation of diblock copolymers at PP/PA(6) interfaces and their role in local crystalline organization under fast heating and cooling conditions”, POLYMER, vol. 53, no. 22, p. 5138-5145, 2012.
    Abstract: Multilayer polypropylene/polyamide 6 (PP/PA(6)) films are commonly obtained by co-extrusion, with PP/PA(6) interfaces reinforced through diblock PP/PA(6) copolymers formed in situ by the reaction of maleic anhydride modified PP on the NH2 end-groups of PA(6) molecules at the contact between the two molten polymers. We present procedures allowing one to form PP/PA(6) thin films assemblies in thermal conditions (fast heating and cooling kinetics, short annealing times) representative of typical co-extrusion conditions. Selective dissolution of the PA(6) part of the assemblies permits to first dose the surface density of copolymer, and second to analyze by AFM imaging the incidence of the copolymer surface density on the crystalline morphology at the interface. These experiments are a first step toward the identification of the key parameters controlling the fracture toughness in these multilayer films. (C) 2012 Elsevier Ltd. All rights reserved.
    Tags: AFM, Coextrusion, Copolymer.

  • L. Bocquet, E. Charlaix, and F. Restagno, “Physics of humid granular media”, COMPTES RENDUS PHYSIQUE, vol. 3, no. 2, p. 207-215, 2002.
    Abstract: A very small amount of liquid added or condensed from a vapor in a granular heap can induce dramatic changes of its static properties. In this paper we review recent advances in humid granular media. We discuss the first approaches for describing the cohesion forces acting between spherical rough beads, and their effect on the maximum avalanche angle of a granular heap. We also discuss the time dependency of these cohesive forces leading to ageing effects in the properties of the medium. (C) 2002 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.
    Tags: adhesion, ageing, capillary condensation, granular media, humidity.

  • L. Champougny, B. Scheid, F. Restagno, J. Vermant, and E. Rio, “Surfactant-induced rigidity of interfaces: a unified approach to free and dip-coated films”, SOFT MATTER, vol. 11, no. 14, p. 2758-2770, 2015.
    Abstract: The behavior of thin liquid films is known to be strongly affected by the presence of surfactants at the interfaces. The detailed mechanism by which the latter enhance film stability is still a matter of debate, in particular concerning the influence of surface elastic effects on the hydrodynamic boundary condition at the liquid/air interfaces. In the present work, “twin” hydrodynamic models neglecting surfactant transport to the interfaces are proposed to describe the coating of films onto a solid plate (Landau-Levich-Derjaguin configuration) as well as soap film pulling (Frankel configuration). Experimental data on the entrained film thickness in both configurations can be fitted very well using a single value of the surface elasticity, which is in good agreement with independent measurements by mean of surface expansion experiments in a Langmuir through. The analysis thus shows that soap films or dip coating experiments may be used to measure the surface elasticity of surfactant solutions in the insoluble limit, namely as long as the film generation dynamics is fast compared to the surfactant adsorption timescale.

  • A. Chenneviere, F. Cousin, F. Boue, E. Drockenmuller, K. R. Shull, L. Leger, and F. Restagno, “Direct Molecular Evidence of the Origin of Slip of Polymer Melts on Grafted Brushes”, MACROMOLECULES, vol. 49, no. 6, p. 2348-2353, 2016.
    Abstract: Neutron reflectivity has been used to investigate the effect of shear on the conformation of hydrogenated polystyrene chains end-grafted on a silicon wafer and covered by a deuterated polystyrene melt, in the grafting regime where the grafted chains at equilibrium extend in the bulk up to their radius of gyration. An experimental setup has been built to shear the samples above their glass transition temperature and then quench them rapidly after the shear. The flow-induced distorted conformation of the end-tethered chains was characterized by neutron reflectivity. We show that the effect of the shear is a decoupling between the grafted chains and the bulk chains which leads to a strong slip of the polymer melt at the solid interface.

  • A. Chenneviere, E. Drockenmuller, D. Damiron, F. Cousin, F. Boue, F. Restagno, and L. Leger, “Quantitative Analysis of Interdigitation Kinetics between a Polymer Melt and a Polymer Brush”, MACROMOLECULES, vol. 46, no. 17, p. 6955-6962, 2013.
    Abstract: We present an investigation of the swelling dynamics of end-grafted hydrogenated polystyrene (h-PS) chains confined between a solid substrate and a deuterated polystyrene (d-PS) melt, based on neutron reflectometry experiments. The segment density profile of the grafted chains was measured for different annealing times. The kinetics of relaxation was quantified by measuring the amount of melt chains that have crossed the initial h-PS/d-PS sharp interface as a function of the annealing time. The dependence of this kinetics versus the molecular weight of the grafted chains, the melt chains, and the grafting density is investigated and compared to a proposed scaling model inspired from the previous work of Milner, McLeish, and O'Connor.(1,2) Moreover, the relaxation kinetics is found to highly depend on the polydispersity of the polymer brushes, and we propose a way for taking that parameter into account.

  • C. Cohen, D. Damiron, S. Ben Dkhil, E. Drockenmuller, F. Restagno, and L. Leger, “Synthesis of well-defined poly(dimethylsiloxane) telechelics having nitrobenzoxadiazole fluorescent chain-ends via thiol-ene coupling”, JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, vol. 50, no. 9, p. 1827-1833, 2012.
    Abstract: Well-defined PDMS telechelics having nitrobenzoxadiazole (NBD) fluorescent probes covalently attached at both chain-ends were prepared in two steps and a series of fractionation procedures starting from commercially available divinyl-terminated PDMS having a broad molar mass dispersity. First, thiol-ene coupling between 6-mercapto-1-hexanol and vinyl chain-ends allowed the formation of dihydroxy-terminated PDMS telechelics through the formation of a thioether linkage. The resulting material was then sequentially fractionated using dichloromethane/methanol mixtures to afford several well-defined dihydroxy-terminated PDMS fractions having sharp distributions of molar masses (Mn = 99.5158 kDa and D < 1.2). The NBD fluorescent probes were then attached at both chain-ends by N,N'-dicyclohexylcarbodiimide/4-(dimethylamino)pyridine esterification coupling between the hydroxyl groups and 6-(7-nitrobenzofurazan-4-ylamino)hexanoic acid. The resulting fluorescent PDMS telechelics were characterized by SEC, 1H NMR, UVvisible, and fluorescence spectroscopies. These materials are suitable probes to investigate the dynamics of polymer chains in bulk or at interfaces by the fringe pattern fluorescent recovery after photobleaching technique. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
    Tags: esterification, fluorescence, functionalization of polymers, NBD, nitrobenzoxadiazole, PDMS, polysiloxanes, silicones, telechelics, thiol-ene coupling, UV-vis spectroscopy.
  • C. Cohen, F. Restagno, C. Poulard, and L. Léger, “Incidence of the molecular organization on friction at soft polymer interfaces”, Soft Matter, vol. 7, no. 18, p. 8535–8541, 2011.
  • C. Cohen, F. Restagno, C. Poulard, and L. Léger, “Wetting and dewetting transition: an efficient toolbox for characterizing low-energy surfaces”, Langmuir, vol. 26, no. 19, p. 15345–15349, 2010.

  • C. Colin, C. R. Pasquier, P. Auban-Senzier, F. Restagno, S. Baudron, P. Batail, and J. Fraxedas, “Transport properties of monocrystalline microwires of EDT-TTF(CONHMe)(2) and (TMTSF)(2)ClO4”, SYNTHETIC METALS, vol. 146, no. 3, p. 273-277, 2004.
    Abstract: The monomolecular compound ethylenedithiotetrathiafulvalene (EDT-TTF(CONHMe)(2)) and the charge transfer salt tetramethyltetraselenafulvalene (TMTSF)(2)ClO4 were successfully recrystallized using the drop casting method. Samples of various sizes were obtained, with widths as small as 300 nm and thicknesses above 30 nm. The length of the samples can reach I mm. The conductivity of the former compound, sigmaapproximate to3.10(-7) S cm(-1) is typical of neutral TTF derivatives. Its bulk mobility is about mu(b)approximate to1 cm(2)/Vs. For the thinnest samples of (TMTSF)(2)ClO4, the two point conductivity is dominated by the sample conductivity instead of the contact resistance. (C) 2004 Elsevier B.V. All rights reserved.
    Tags: drop casting, electrical conductivity, microwires, organic compound, tetrathiafulvalene.

  • C. Cottin-Bizonne, S. Jurine, J. Baudry, J. Crassous, F. Restagno, and E. Charlaix, “Nanorheology: An investigation of the boundary condition at hydrophobic and hydrophilic interfaces”, EUROPEAN PHYSICAL JOURNAL E, vol. 9, no. 1, p. 47-53, 2002.
    Abstract: It has been shown that the flow of a simple liquid over a solid surface can violate the so-called no-slip boundary condition. We investigate the flow of polar liquids, water and glycerol, on a hydrophilic Pyrex surface and a hydrophobic surface made of a Self-Assembled Monolayer of OTS (octadecyltrichlorosilane) on Pyrex. We use a Dynamic Surface Force Apparatus (DSFA) which allows one to study the flow of a liquid film confined between two surfaces with a nanometer resolution. No-slip boundary conditions are found for both fluids on hydrophilic surfaces only. Significant slip is found on the hydrophobic surfaces,with a typical length of one hundred nanometers.
  • C. Cottin-Bizonne, S. Jurine, J. Baudry, J. Crassous, F. Restagno, and E. Charlaix, “Influence of the wetting properties on the flow boundary condition at a solid interface”, HOUILLE BLANCHE-REVUE INTERNATIONALE DE L EAU, no. 5, p. 116-119, 2003.
    Abstract: We report here experiments with a Dynamic Surface Force Apparatus (DSFA) to investigate the flow boundary condition of glycerol at a solid surface. We use hydrophilic Pyrex surfaces and hydrophobic surfaces made of a Self-Assembled Monolayer of OTS (octadecyltrichlorosilane) on Pyrex. The DSFA allows us to study the flow of a liquid film confined between two surfaces with a nanometer resolution. No-slip boundary conditions are found for glycerol on hydrophilic surfaces only. Significant slip is found on the hydrophobic surfaces, with a typical length of one hundred nanometers.
  • K. Dalnoki-Veress, T. Salez, and F. Restagno, “Why can't you separate interleaved books?”, PHYSICS TODAY, vol. 69, no. 6, p. 74-75, 2016.

  • E. Degrandi-Contraires, A. Beaumont, F. Restagno, R. Weil, C. Poulard, and L. Leger, “Cassie-Wenzel-like transition in patterned soft elastomer adhesive contacts”, EPL, vol. 101, no. 1, 2013.
    Abstract: We present an experimental and theoretical analysis of the transition from top to mixed top and full contacts between a smooth elastomer sphere and an elastomer substrate micropatterned with hexagonal arrays of cylindrical pillars. We show that surprisingly the overall behavior of the apparent radius of contact vs. the applied load obeys JKR contact mechanics, whatever the nature of the contact (top or mixed). This allows us to propose a mechanical description predicting quantitatively the evolution of the critical load for the onset of full contact with the pattern geometry and qualitatively that of the area of full contact above this threshold. We emphasize the role of the mechanical coupling between the pillars induced by the deformation of the substrate for large enough densities of pillars. Copyright (C) EPLA, 2013
  • E. Degrandi-Contraires, C. Poulard, F. Restagno, and L. Léger, “Sliding friction at soft micropatterned elastomer interfaces”, Faraday discussions, vol. 156, no. 1, p. 255–265, 2012.

  • J. Delacotte, L. Montel, F. Restagno, B. Scheid, B. Dollet, H. A. Stone, D. Langevin, and E. Rio, “Plate Coating: Influence of Concentrated Surfactants on the Film Thickness”, LANGMUIR, vol. 28, no. 8, p. 3821-3830, 2012.
    Abstract: We present a large range of experimental data concerning the influence of surfactants on the well-known Landau-Levich-Derjaguin experiment where a liquid film is generated by pulling a plate out of a bath. The thickness h of the film was measured as a function of the pulling velocity V for different kinds of surfactants (C12E6, which is a nonionic surfactant, and DeTAB and DTAB, which are ionic) and at various concentrations near and above the critical micellar concentration (cmc). We report the thickening factor alpha = h/h(LLD), where h(LLD) is the film thickness obtained without a surfactant effect, i.e., as for a pure fluid but with the same viscosity and surface tension as the surfactant solution, over a wide range of capillary numbers (Ca = eta V/gamma, with eta being the surfactant solution viscosity and gamma its surface tension) and identify three regimes: (i) at small Ca alpha is large due to confinement and surface elasticity (or Marangoni) effects, (ii) for increasing Ca there is an intermediate regime where alpha decreases as Ca increases, and (iii) at larger (but still small) Ca alpha is slightly higher than unity due to surface viscosity effects. In the case of nonionic surfactants, the second regime begins at a fixed Ca, independent of the surfactant concentration, while for ionic surfactants the transition depends on the concentration, which we suggest is probably due to the existence of an electrostatic barrier to surface adsorption. Control of the physical chemistry at the interface allowed us to elucidate the nature of the three regimes in terms of surface rheological properties.

  • J. Delacotte, E. Rio, F. Restagno, C. Uzuem, R. von Klitzing, and D. Langevin, “Viscosity of Polyelectrolytes Solutions in Nanofilms”, LANGMUIR, vol. 26, no. 11, p. 7819-7823, 2010.
    Abstract: We use a thin film pressure balance to probe the rheological properties of thin liquid films. These films are made from mixed aqueous solutions of surfactants and polyelectrolytes. They drain under applied pressure in a noncontinuous way due to a stratification process of the polyelectrolytes network. The stratification kinetics was studied for films stabilized by different surfactants. Using a theoretical model, it is possible to examine the effect of both the surfactant and the film thickness on the local dissipation. On one hand, it was observed that dissipation depends on the polyelectrolyte concentration only, regardless whether the surfactant is neutral or bears electric charges opposite to those of the polyelectrolyte. On the other hand, it was found that dissipation is stronger in thinner films.
  • L. Dies, F. Restagno, R. Weil, L. Léger, and C. Poulard, “Role of adhesion between asperities in the formation of elastic solid/solid contacts”, The European Physical Journal E, vol. 38, no. 12, p. 1–8, 2015.
  • M. Dirany, L. Dies, F. Restagno, L. Leger, C. Poulard, and G. Miquelard-Garnier, “Chemical modification of PDMS surface without impacting the viscoelasticity: Model systems for a better understanding of elastomer/elastomer adhesion and friction”, Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 468, p. 174–183, 2015.
    Tags: Contact angle, Hydrosilylation, Poly(dimethylsiloxane) elastomers, Surface energy, Surface modification, Viscoelastic properties.

  • M. Hénot, A. Chennevière, E. Drockenmuller, K. Shull, L. Léger, and F. Restagno, “Influence of grafting on the glass transition temperature of PS thin films”, The European Physical Journal E, vol. 40, no. 1, 2017.

  • S. Jones, E. Rio, C. Cazeneuve, L. Nicolas-Morgantini, F. Restagno, and G. S. Luengo, “Tribological influence of a liquid meniscus in human sebum cleaning”, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, vol. 498, p. 268-275, 2016.
    Abstract: The interaction of surfactants in solution with hydrophobic materials is at the root of the process of detergency. Lipid containing micelles are formed in solution, and through water rinsing, these structures are washed out from the surface. The presence of air in the solution and the formation of foam add complexity to the system due to the increased proportion of water interfaces in contact with the surface. The latter situation is more difficult to understand. In this work, we propose, as a first step, to explore the role of the interfaces in cleaning silicon wafers previously coated with a model lipid mixture representing human sebum has been investigated. It turns out that the presence of interfaces enhances the cleaning efficiency. The effect of altering the surface properties of the silicon wafer was also investigated and it was found that changing the contact angle of the wafer brought a very strong effect on the cleaning efficiency. (C) 2016 Elsevier B.V. All rights reserved.
    Tags: Detergency, Foam-oil interaction, Surface energy.

  • A. Korolkovas, C. Rodriguez-Emmenegger, A. de los Santos Pereira, A. Chennevière, F. Restagno, M. Wolff, F. A. Adlmann, A. J. C. Dennison, and P. Gutfreund, “Polymer Brush Collapse under Shear Flow”, Macromolecules, Feb. 2017.

  • S. Leroy, F. Restagno, and E. Charlaix, “Fine calibration of the residual dissipation in a surface forces apparatus using a capacitive sensor”, REVIEW OF SCIENTIFIC INSTRUMENTS, vol. 80, no. 8, 2009.
    Abstract: The design of a dynamic surface force apparatus using a capacitive sensor has been useful in the past to study the nanorheological behavior of thin liquid films confined between a sphere and a plane. This allows a precise measurement of the hydrodynamical boundary condition of liquids down to some molecular sizes. However for thick liquid films, the viscous force is decreased and the dissipation due to the flow of air in the capacitive sensor becomes of the same order of magnitude than the force due to the liquid flow. In the present paper we present an original technique to characterize this residual force due to the capacitive sensor and we show that a precise subtraction of this force extends the precision of the device to the case of thick liquid films of low viscosity. This correction should be of major importance to extend the capability of surface forces apparatus to measure very large boundary slippage of simple liquids. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3187223]

  • S. Leroy, A. Steinberger, C. Cottin-Bizonne, F. Restagno, L. Leger, and E. Charlaix, “Hydrodynamic Interaction between a Spherical Particle and an Elastic Surface: A Gentle Probe for Soft Thin Films”, PHYSICAL REVIEW LETTERS, vol. 108, no. 26, 2012.
    Abstract: We study the hydrodynamic interaction between a sphere and an elastic surface at a nanoscale with a dynamic surface force apparatus. We show that the interplay between viscous forces and elastic deformations leads to very rich scaling properties of the force response, providing a unique signature of the surface elastic behavior. These properties are illustrated on three different examples: a thick elastomer, a thin elastomer film, and a layer of micrometric bubbles. We show that this fluid probing allows one to measure the Young's modulus of surfaces and soft thin layers at distance, without any direct solid-solid contact.

  • E. Lorenceau, F. Restagno, and D. Quere, “Fracture of a viscous liquid”, PHYSICAL REVIEW LETTERS, vol. 90, no. 18, 2003.
    Abstract: When a viscous liquid hits a pool of liquid of the same nature, the impact region is hollowed by the shock. Its bottom becomes extremely sharp if increasing the impact velocity, and we report that the curvature at that place increases exponentially with the flow velocity, in agreement with a theory by Jeong and Moffatt. Such a law defines a characteristic velocity for the collapse of the tip, which explains both the cusplike shape of this region, and the instability of the cusp if increasing (slightly) the impact velocity. Then, a film of the upper phase is entrained inside the pool. We characterize the critical velocity of entrainment of this phase and compare our results with recent predictions by Eggers.

  • M. Maleki, M. Reyssat, F. Restagno, D. Quere, and C. Clanet, “Landau-Levich menisci”, JOURNAL OF COLLOID AND INTERFACE SCIENCE, vol. 354, no. 1, p. 359-363, 2011.
    Abstract: As shown by Landau, Levich and Derjaguin, a plate withdrawn out of a wetting bath at low capillary numbers deforms the very top of the liquid reservoir. At this place, a dynamic meniscus forms, whose shape and curvature select the thickness of the film entrained by the plate. In this paper, we measure accurately the thickness of the entrained film by reflectometry, and characterize the dynamic meniscus, which is found to decay exponentially towards the film. We show how this shape is modified when reversing the motion: as a plate penetrates the bath, the dynamic meniscus can “buckle” and present a stationary wavy profile, which we discuss. (C) 2010 Elsevier Inc. All rights reserved.
    Tags: Dip coating, Dynamic meniscus, Lubrication, Wavy film, wetting.

  • C. Poulard, F. Restagno, R. Weil, and L. Léger, “Mechanical tuning of adhesion through micro-patterning of elastic surfaces”, Soft matter, vol. 7, no. 6, p. 2543–2551, 2011.

  • F. Restagno, L. Bocquet, and T. Biben, “Metastability and nucleation in capillary condensation”, PHYSICAL REVIEW LETTERS, vol. 84, no. 11, p. 2433-2436, 2000.
    Abstract: This paper is devoted to thermally activated dynamics of capillary condensation. On the basis of a simple model we identify the critical nucleus involved in the transition mechanism and calculate the nucleation barrier from which we obtain information on the nucleation time. Close to the condensation point, the theory predicts extremely large energy barriers leading to strong metastabilities, long time dependencies, and large hysteresis in agreement with experimental observations in mesoporous media. The validity of the model is assessed using a numerical simulation of a time-dependent Ginzburg-Landau model for the confined system.

  • F. Restagno, L. Bocquet, T. Biben, and E. Charlaix, “Thermally activated dynamics of capillary condensation”, JOURNAL OF PHYSICS-CONDENSED MATTER, vol. 12, no. 8A, p. A419-A424, 2000.
    Abstract: This paper is devoted to the thermally activated dynamics of capillary condensation. We present a simple model which enables us to identify the critical nucleus involved in the transition mechanism. This simple model is then applied to calculate the nucleation barrier from which we can obtain information on the nucleation time. We present a simple estimation of the nucleation barrier in slab geometry both in the two-dimensional case and in the three-dimensional case. We extend the model to the case of rough surfaces which is closer to the experimental case and allows comparison with experimental data.

  • F. Restagno, L. Bocquet, and E. Charlaix, “Where does a cohesive granular heap break?”, EUROPEAN PHYSICAL JOURNAL E, vol. 14, no. 2, p. 177-183, 2004.
    Abstract: In this paper, we consider the effect of cohesion on the stability of a granular heap and compute the maximum angle of stability of the heap as a function of the cohesion. We show that the stability is strongly affected by the dependence of the cohesion on the local pressure. In particular, this dependence is found to determine the localization of the failure plane. While for a constant adhesion force, slip occurs deep inside the heap, surface failure is obtained for a linear variation of the cohesion on the normal stress. Such a transition allows to interpret some recent experimental results on cohesive materials.

  • F. Restagno, L. Bocquet, J. Crassous, and E. Charlaix, “Slow kinetics of capillary condensation in confined geometry: experiment and theory”, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, vol. 206, no. 1-3, SI, p. 69-77, 2002.
    Abstract: When two solid surfaces are brought in contact, water vapor present in the ambient air may condense in the region of the contact to form a liquid bridge connecting the two surfaces: this is the so-called capillary condensation. This phenomenon has drastic consequences on the contact between solids, modifying the macroscopic adhesion and friction properties. In this paper, we present a survey of the work we have performed both experimentally and theoretically to understand the microscopic foundations of the kinetics of capillary condensation. From the theoretical point of view, we have computed the free energy barrier associated with the condensation of the liquid from the gas in a confined system. These calculations allow understanding of the existence of very large hysteresis, which is often associated with capillary condensation. These results are compatible with experimental results obtained with a surface forces apparatus in a vapor atmosphere, showing a large hysteresis of the surface energy of two parallel planes as a function of their distance. In the second part, we present some experiments on the influence of humidity on the avalanche angle of granular media. We show that the aging in time of this avalanche angle can be explained by the slow kinetics of capillary condensation in a random confined geometry. (C) 2002 Elsevier Science B.V. All rights reserved.
    Tags: capillary condensation, granular, surface forces apparatus.

  • F. Restagno, J. Crassous, E. Charlaix, C. Cottin-Bizonne, and M. Monchanin, “A new surface forces apparatus for nanorheology”, REVIEW OF SCIENTIFIC INSTRUMENTS, vol. 73, no. 6, p. 2292-2297, 2002.
    Abstract: We present an original surface forces apparatus which enables us to measure the interaction forces between any solid surfaces such as, e.g., metallic surfaces, opaque surfaces, or rough surfaces. The relative displacement of the surfaces is measured with a capacitive sensor. The forces are measured by a stiff and highly sensitive interferometric sensor. The measurements are performed in a dc to 100 Hz bandwidth. This feature allows us to study the mechanical response of a nanometric confined medium to rapid strain variations in the linear regime. An example of nanorheological measurement of dodecane confined in a nanometric gap is given at the end of this article. (C) 2002 American Institute of Physics.

  • F. Restagno, J. Crassous, E. Charlaix, and M. Monchanin, “A new capacitive sensor for displacement measurement in a surface-force apparatus”, MEASUREMENT SCIENCE AND TECHNOLOGY, vol. 12, no. 1, p. 16-22, 2001.
    Abstract: We present a new capacitive sensor for displacement measurement in a surface-force apparatus which allows dynamical measurements in the range 0-100 Hz. This sensor measures the relative displacement between two macroscopic opaque surfaces over periods of time ranging from milliseconds to, in principle, an indefinite period, at a very low price and down to atomic resolution. It consists of a plane capacitor, a high frequency oscillator and a high sensitivity frequency-to-voltage converter. We use this sensor to study the nanorheological properties of dodecane confined between glass surfaces.
    Tags: capacitive sensor, nanorheology, surface forces apparatus.

  • F. Restagno, J. Crassous, C. Cottin-Bizonne, and E. Charlaix, “Adhesion between weakly rough beads”, PHYSICAL REVIEW E, vol. 65, no. 4, 1, 2002.
    Abstract: Cohesion effects are of prime importance in powders and granular media, and they are strongly affected by the roughness of the grain surface. We report measurements of the adhesion force between surfaces of Pyrex having a nanometric roughness, with a surface force apparatus. The two surfaces are immersed in liquid n-dodecane. The adhesion force measured is much smaller than expected in the case of smooth surfaces. We find that the adhesion force depends on the maximal load that has been applied on the surfaces, but does not depend on the time during which they have been in contact. We propose a model of plastic deformation of the small asperities in a macroscopic Hertz contact which is in good agreement with the experimental data.

  • F. Restagno, H. Gayvallet, L. Bocquet, and E. Charlaix, “Humidity effects and aging behavior in granular media”, in DYNAMICS IN SMALL CONFINING SYSTEMS IV, 506 KEYSTONE DRIVE, WARRENDALE, PA 15088-7563 USA, 1999, vol. 543, p. 363-368.
    Abstract: We present a study of humidity effects on the maximum stability angle in granular media. We show that a granular medium of small glass beads exhibits aging properties : the first avalanche angle increases logarithmically with the resting time of the pile. This aging behavior is found to depend on the relative humidity of the surrounding atmosphere. A short interpretation of this effect, based on a model of activated capillary condensation, is proposed.

  • F. Restagno, C. Ursini, H. Gayvallet, and E. Charlaix, “Aging in humid granular media”, PHYSICAL REVIEW E, vol. 66, no. 2, 1, 2002.
    Abstract: Aging behavior is an important effect in the friction properties of solid surfaces. In this paper we investigate the temporal evolution of the static properties of a granular medium by studying the aging over time of the maximum stability angle of submillimetric glass beads. We report the effect of several parameters on these aging properties, such as the wear on the beads, the stress during the resting period, and the humidity content of the atmosphere. Aging effects in an ethanol atmosphere are also studied. These experimental results are discussed at the end of the paper.
  • F. Restagno, C. Poulard, C. Cohen, L. Vagharchakian, and L. Léger, “Contact angle and contact angle hysteresis measurements using the capillary bridge technique”, Langmuir, vol. 25, no. 18, p. 11188–11196, 2009.

  • L. Saulnier, L. Champougny, G. Bastien, F. Restagno, D. Langevin, and E. Rio, “A study of generation and rupture of soap films”, SOFT MATTER, vol. 10, no. 16, p. 2899-2906, 2014.
    Abstract: What are the lifetime and maximum length of a soap film pulled at a velocity V out of a bath of soapy solution? This is the question we explore in this article by performing systematic film rupture experiments. We show that the lifetime and maximal length of the films are fairly reproducible and controlled only by hydrodynamics. For surfactants with high surface elastic modulus, we argue that the rupture is triggered by the expansion of a thinning zone at the top of the film. The length l(tz) of this zone expands with time at a velocity equal to V/2, which can be obtained by a balance between gravity and viscous forces. The film lifetime is then found to decrease with the pulling velocity V, which implies that the surface tension gradient along the film increases with V. This surface tension gradient is found to be surprisingly small. Finally, the lifetime of films stabilised by solutions with small surface elastic modulus turns out to be much shorter than the ones for films with rigid interfaces.

  • L. Saulnier, F. Restagno, J. Delacotte, D. Langevin, and E. Rio, “What Is the Mechanism of Soap Film Entrainment?”, LANGMUIR, vol. 27, no. 22, p. 13406-13409, 2011.
    Abstract: Classical Frankel's law describes the formation of soap films and their evolution upon pulling, a model situation of film dynamics in foams (formation, rheology, and destabilization). With the purpose of relating film pulling to foam dynamics, we have built a new setup able to give an instantaneous measurement of film thickness, thus allowing us to determine film thickness profile during pulling. We found that only the lower part of the film is of uniform thickness and follows Frankel's law, provided the entrainment velocity is small. We show that this is due to confinement effects: there is not enough surfactant in the bulk to fully cover the newly created surfaces which results in immobile film surfaces. At large velocities, surfaces become mobile and then Frankel's law breaks down, leading to a faster drainage and thus to a nonstationary thickness at the bottom of the film. These findings should help in understanding the large dispersion of previous experimental data reported during the last 40 years and clarifying the pulling phenomenon of thin liquid films.

  • B. Scheid, J. Delacotte, B. Dollet, E. Rio, F. Restagno, E. A. van Nierop, I. Cantat, D. Langevin, and H. A. Stone, “The role of surface rheology in liquid film formation”, EPL, vol. 90, no. 2, 2010.
    Abstract: The role of surface rheology in fundamental fluid dynamical systems, such as liquid coating flows and soap film formation, is poorly understood. We investigate the role of surface viscosity in the classical film-coating problem. We propose a theoretical model that predicts film thickening based on a purely surface-viscous theory. The theory is supported by a set of new experimental data that demonstrates slight thickening even at very high surfactant concentrations for which Marangoni effects are irrelevant. The model and experiments represent a new regime that has not been identified before. Copyright (C) EPLA, 2010

  • L. Vagharchakian, F. Restagno, and L. Leger, “Capillary Bridge Formation and Breakage: A Test to Characterize Antiadhesive Surfaces”, JOURNAL OF PHYSICAL CHEMISTRY B, vol. 113, no. 12, p. 3769-3775, 2009.
    Abstract: In order to characterize very weak adhesive surfaces, we have developed a quantitative test inspired by the Johnson, Kendall, and Roberts adhesion test for soft adhesives, which relies on the formation and then the rupture of a capillary bridge between the surface to be tested and a liquid bath. Both the shape and the kinetics of breakage of the capillary bridge for various coatings put into contact with liquids of various viscosities and surface tensions have been studied. Several pull off regimes can be distinguished. For low pull off velocities, a quasi-static regime is observed, well described by capillary equations and sensitive to the hysteresis of the contact angle of the fluid on the coating. Above a critical pull off velocity that depends on the fluid viscosity, a dynamic regime is observed, characterized by the formation of a flat pancake of fluid on the coating that recedes more slowly than the capillary bridge itself. After the breakage of the capillary bridge, a small drop can remain attached to the surface. The volume of this drop depends on the dynamical regime and is strongly affected by very small differences between the coatings. The aptitude of this test in characterizing very weakly adhesive surfaces is exemplified by a comparison between three different perfluorinated coatings.

  • R. Villey, E. Martinot, C. Cottin-Bizonne, M. Phaner-Goutorbe, L. Leger, F. Restagno, and E. Charlaix, “Effect of Surface Elasticity on the Rheology of Nanometric Liquids”, PHYSICAL REVIEW LETTERS, vol. 111, no. 21, 2013.
    Abstract: The rheological properties of liquids confined to nanometer scales are important in many physical situations. In this Letter, we demonstrate that the long-range elastic deformation of the confining surfaces must be taken into account when considering the rheology of nanometric liquids. In the case of a squeeze-flow geometry, we show that below a critical distance D-c, the liquid is clamped by its viscosity and its intrinsic properties cannot be disentangled from the global system response. Using nanorheology experiments, we demonstrate that picometer elastic deflections of the rigid confining surfaces dominate the overall mechanical response of nanometric liquids confined between solid walls.

  • Y. Zhu, A. Bironeau, F. Restagno, C. Sollogoub, and G. Miquelard-Garnier, “Kinetics of thin polymer film rupture: Model experiments for a better understanding of layer breakups in the multilayer coextrusion process”, POLYMER, vol. 90, p. 156-164, 2016.
    Abstract: We show that the kinetics of bursting of a thin film embedded in another polymer matrix can be well described by a simple equation balancing the viscous and capillary forces. The role of viscosity, interfacial tension and thickness of the layers under static conditions was investigated by adapting a simple model experiment initially designed to study the dewetting of a thin polymer film on another polymer substrate. Kinetics was correlated to instabilities occurring during multilayer coextrusion leading to the break-up of layers below a critical nanometric thickness. The results suggest that shear and elongation forces during the process actually stabilize the layers. Understanding these instabilities is of great interest since this innovative process showed potential to design at an industrial scale macromolecular materials displaying new macroscopic properties, due to interfacial and confinement effects. However, instabilities leading to the breaking of these nanometric layers will alter final properties (optical, gas barrier.). (C) 2016 Elsevier Ltd. All rights reserved.
    Tags: Dewetting, Multilayer coextrusion, Thin film.
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