Université PSL



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- Pour toute publication de résultats ayant reçu l’aide de l’IPGG (présence dans les locaux de l’IPGG, passage sur la plateforme technologique de l’IPGG, collaboration inter équipes IPGG, lié à une bourse doctorale ou postdoctorale IPGG, ou encore utilisation des espaces communs), il vous faut indiquer  cette phrase « Ce travail a été réalisé avec le soutien du laboratoire d’excellence Institut Pierre-Gilles de Gennes (programme Investissements d’avenir ANR-10-IDEX-0001-02 PSL et ANR-10-LABX-31). » / « This work has received the support of "Institut Pierre-Gilles de Gennes" (laboratoire d’excellence, “Investissements d’avenir” program ANR-10-IDEX-0001-02 PSL and ANR-10-LABX-31.). ».

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Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions
Laboratoire Indysoft - Gabriel Guyard Alexandre Vilquin Nicolas Sanson Frederic Restagno Joshua D. Mcgraw
HAL - 1 - https://hal.archives-ouvertes.fr/hal-03029154 - 2020
Understanding confined flows of complex fluids requires simultaneous access to the mechanical behaviour of the liquid and the boundary condition at the interfaces. Here, we use evanescent wave microscopy to investigate near-surface flows of semi-dilute, unentangled polyacrylamide solutions. By using both neutral and anionic polymers, we show that monomer charge plays a key role in confined polymer dynamics. For solutions in contact with glass, the neutral polymers display chain-sized adsorbed layers, while a shear-rate-dependent apparent slip length is observed for anionic polymer solutions. The slip lengths measured at all concentrations collapse onto a master curve when scaled using a simple two-layer depletion model with non-Newtonian viscosity. A transition from an apparent slip boundary condition to a chain-sized adsorption layer is moreover highlighted by screening the charge with additional salt in the anionic polymer solutions. We anticipate that our study will be a starting point for more complex studies relating the polymer dynamics at interfaces to their chemical and physical composition.
Interface-Sensitive Raman Microspectroscopy of Water via Confinement with a Multimodal Miniature Surface Forces Apparatus
Laboratoire INDYSOFT - Hilton B. de Aguiar, Joshua D. McGraw, and Stephen H. Donaldson Jr.
Langmuir - 35(48) 15543–15551 - doi.org/10.1021/acs.langmuir.9b01889 - 2020
Modern interfacial science is increasingly multidisciplinary. Unique insight into interfacial interactions requires new multimodal techniques for interrogating surfaces with simultaneous complementary physical and chemical measurements. Here, we describe the design and testing of a microscope that incorporates a miniature surface forces apparatus (μSFA) in sphere vs flat geometry for force–distance measurements, while simultaneously acquiring Raman spectra of the confined zone. The simple optical setup isolates independent optical paths for (i) the illumination and imaging of Newton’s rings and (ii) Raman scattering excitation and efficient signal collection. We benchmark the methodology by examining Teflon thin films in asymmetric (Teflon–water–glass) and symmetric (Teflon–water–Teflon) configurations. Water is observed near the Teflon–glass interface with nanometer-scale sensitivity in both the distance and Raman signals. We perform chemically resolved, label-free imaging of confined contact regions between Teflon and glass surfaces immersed in water. Remarkably, we estimate that the combined approach enables vibrational spectroscopy with single water monolayer sensitivity within minutes. Altogether, the Raman-μSFA allows exploration of molecular confinement between surfaces with chemical selectivity and correlation with interaction forces.
Multimodal Miniature Surface Forces Apparatus (μSFA) for Interfacial Science Measurements
Laboratoire INDYSOFT - Kai Kristiansen, Stephen H. Donaldson Jr., Zachariah J. Berkson, Jeffrey Scott, Rongxin Su, Xavier Banquy, Dong Woog Lee, Hilton B. de Aguiar, Joshua D. McGraw, George D. Degen, and Jacob N. Israelachvili
Langmuir - 35(48) 15500–15514 - doi.org/10.1021/acs.langmuir.9b01808 - 2020
Advances in the research of intermolecular and surface interactions result from the development of new and improved measurement techniques and combinations of existing techniques. Here, we present a new miniature version of the surface forces apparatus—the μSFA—that has been designed for ease of use and multimodal capabilities with the retention of the capabilities of other SFA models including accurate measurements of the surface separation distance and physical characterization of dynamic and static physical forces (i.e., normal, shear, and friction) and interactions (e.g., van der Waals, electrostatic, hydrophobic, steric, and biospecific). The small physical size of the μSFA, compared to previous SFA models, makes it portable and suitable for integration into commercially available optical and fluorescence light microscopes, as demonstrated here. The large optical path entry and exit ports make it ideal for concurrent force measurements and spectroscopy studies. Examples of the use of the μSFA in combination with surface plasmon resonance (SPR) and Raman spectroscopy measurements are presented. Because of the short working distance constraints associated with Raman spectroscopy, an interferometric technique was developed and applied to calculate the intersurface separation distance based on Newton’s rings. The introduction of the μSFA will mark a transition in SFA usage from primarily physical characterization to concurrent physical characterization with in situ chemical and biological characterization to study interfacial phenomena, including (but not limited to) molecular adsorption, fluid flow dynamics, the determination of surface species and morphology, and (bio)molecular binding kinetics.
Time dependence of advection-diffusion coupling for nanoparticle ensembles
Laboratoire INDYSOFT - Alexandre Vilquin Vincent Bertin Pierre Soulard Gabriel Guyard Elie Raphaël Frederic Restagno Thomas Salez Joshua Mcgraw
HAL - 1 - https://hal.archives-ouvertes.fr/hal-02896493 - 2020
Particle transport in fluids at micro-and nano-scales is important in many domains. As compared to the quiescent case, the time evolution of particle dispersion is enhanced by coupling: i) advection along the flow; and ii) diffusion along the associated velocity gradients. While there is a well-known, long-time limit for this advection-diffusion enhancement, understanding the short-time limit and corresponding crossover between these two asymptotic limits is less mature. We use evanescent-wave video microscopy for its spatio-temporal resolution. Specifically, we observe a near-surface zone of where the velocity gradients, and thus dispersion, are the largest within a simple microfluidic channel. Supported by a theoretical model and simulations based on overdamped Langevin dynamics, our experiments reveal the crossover of this so-called Taylor dispersion from short to long time scales. Studying a range of particle size, viscosity and applied pressure, we show that the initial spatial distribution of particles can strongly modify observed master curves for short-time dispersion and its crossover into the long-time regime.
Influence of outer-layer finite-size effects on the dewetting dynamics of a thin polymer film embedded in an immiscible matrix
Laboratoire INDYSOFT - M. S. Chebil,a J. D. McGraw, T. Salez, C. Sollogoub and G. Miquelard-Garnier
Soft Matter - 14 6256-6263 - doi.org/10.1039/C8SM00592C - 2020
In capillary-driven fluid dynamics, simple departures from equilibrium offer the chance to quantitatively model the resulting relaxations. These dynamics in turn provide insight on both practical and fundamental aspects of thin-film hydrodynamics. In this work, we describe a model trilayer dewetting experiment elucidating the effect of solid, no-slip confining boundaries on the bursting of a liquid film in a viscous environment. This experiment was inspired by an industrial polymer processing technique, multilayer coextrusion, in which thousands of alternating layers are stacked atop one another. When pushed to the nanoscale limit, the individual layers are found to break up on time scales shorter than the processing time. To gain insight on this dynamic problem, we here directly observe the growth rate of holes in the middle layer of the trilayer films described above, wherein the distance between the inner film and solid boundary can be orders of magnitude larger than its thickness. Under otherwise identical experimental conditions, thinner films break up faster than thicker ones. This observation is found to agree with a scaling model that balances capillary driving power and viscous dissipation with a no-slip boundary condition at the solid substrate/viscous environment boundary. In particular, even for the thinnest middle-layers, no finite-size effect related to the middle film is needed to explain the data. The dynamics of hole growth is captured by a single master curve over four orders of magnitude in the dimensionless hole radius and time, and is found to agree well with predictions including analytical expressions for the dissipation.
Adsorption-induced slip inhibition for polymer melts on ideal substrates
Laboratoire INDYSOFT - Mark Ilton, Thomas Salez, Paul D. Fowler, Marco Rivetti, Mohammed Aly, Michael Benzaquen, Joshua D. McGraw, Elie Raphaël, Kari Dalnoki-Veress & Oliver Bäumchen
Nat Commun - 9 1172 - doi.org/10.1039/C8SM00592C - 2020
Hydrodynamic slip, the motion of a liquid along a solid surface, represents a fundamental phenomenon in fluid dynamics that governs liquid transport at small scales. For polymeric liquids, de Gennes predicted that the Navier boundary condition together with polymer reptation implies extraordinarily large interfacial slip for entangled polymer melts on ideal surfaces; this Navier-de Gennes model was confirmed using dewetting experiments on ultra-smooth, low-energy substrates. Here, we use capillary leveling—surface tension driven flow of films with initially non-uniform thickness—of polymeric films on these same substrates. Measurement of the slip length from a robust one parameter fit to a lubrication model is achieved. We show that at the low shear rates involved in leveling experiments as compared to dewetting ones, the employed substrates can no longer be considered ideal. The data is instead consistent with a model that includes physical adsorption of polymer chains at the solid/liquid interface.
Self-Similar Relaxation of Confined Microfluidic Droplets
Laboratoire INDYSOFT - Margaux Kerdraon1, Joshua D. McGraw1, Benjamin Dollet2, and Marie-Caroline Jullien
Phys. Rev. Lett. - 123 024501 - doi.org/10.1103/PhysRevLett.123.024501 - 2020
We report an experimental study concerning the capillary relaxation of a confined liquid droplet in a microscopic channel with a rectangular cross section. The confinement leads to a droplet that is extended along the direction normal to the cross section. These droplets, found in numerous microfluidic applications, are pinched into a peanutlike shape thanks to a localized, reversible deformation of the channel. Once the channel deformation is released, the droplet relaxes back to a pluglike shape. During this relaxation, the liquid contained in the central pocket drains towards the extremities of the droplet. Modeling such viscocapillary droplet relaxation requires considering the problem as 3D due to confinement. This 3D consideration yields a scaling model incorporating dominant dissipation within the droplet menisci. As such, the self-similar droplet dynamics is fully captured.

7 publications.