arXiv subjects

Pascal Damman

Publications and source records attributed to Pascal Damman.

17 recordsLinked to original sources

arXiv2026

Viscoelasticity Enhances Contactless Adhesion of Soft Substrates

Understanding adhesion is essential for describing stability, friction, and interfacial dynamics. Here, we investigate the adhesion force dynamics between a rigid sphere and a soft surface without direct contact, mediated by a viscous fluid. By combining controlled experiments, a first-principles visco-elastohydrodynamic theory, and numerical simulations, we demonstrate that viscoelastic relaxation fundamentally modifies elastohydrodynamic adhesion. Rather than simply dissipating energy, viscoelasticity causes the substrate to behave transiently as a stiffer solid, enhancing the maximum adhesive force, changing the early-time force growth for $t^{2/3}$ to $t^{1/3}$, shortening the interaction time, and giving rise to new scaling laws governed by the Deborah number. The two proposed dimensionless parameters, the softness parameter and the Deborah number, define a unified phase diagram connecting three distinct adhesion regimes: classical Reynolds lubrication, elastohydrodynamic adhesion, and the newly identified visco-elastohydrodynamic regime.

cond-mat.soft↗

arXiv2026

Broadband molecular dynamics simulation of fluid inertial effects in confined Brownian motion

Hydrodynamic memory governs Brownian motion over a broad range of timescales, from acoustic wave propagation at short times to diffusive relaxation at long times. While confinement-induced corrections to Brownian diffusion are well established, how confinement modifies the full hydrodynamic response remains less explored. In this Letter, we use molecular-dynamics simulations of a neutrally buoyant colloidal particle in an explicit solvent to resolve the velocity autocorrelation function across a broad hydrodynamic spectrum. In the bulk, the simulations recover compressibility, added mass, the hydrodynamic long-time tail, and Stokes-Einstein diffusion without adjustable parameters. Near a rigid wall, the velocity correlations become anisotropic, their algebraic tails are modified, and the diffusion coefficients are reduced. Most importantly, the short-time dynamics reveals a pronounced enhancement of the effective added mass as the wall is approached. As such, the velocity autocorrelation function appears as a central quantity to bridge the zero-frequency mobility and the high-frequency inertial behaviour of a confined Brownian particle.

cond-mat.soft↗

arXiv2026

Enhanced viscous adhesion using deformable structure

We investigate the adhesion dynamics of a thin elastic structure in contact with a viscous fluid and retracted at a controlled speed, mimicking natural adhesion mechanisms. During detachment, the viscous fluid confined between the deformable structure and a rigid substrate generates an adhesive force due to a pressure drop within the thin film. We show from dedicated experiments that the structural flexibility introduces a strongly nonlinear mechanical response, which significantly alters both the magnitude and the evolution of the adhesion force with retraction velocity. In contrast to rigid systems, the deformability of the structure enables enhanced and tunable adhesion. To capture this interplay, we develop a theoretical framework that couples elasticity and viscosity, providing new insights into how flexible structures enable adhesion control.

cond-mat.soft↗

arXiv2026

Universal wrinkling dynamics of a sheet on viscous liquid

We investigate the wrinkling dynamics of a thin elastic sheet that is indented or compressed while floating on a viscous liquid. We show that the deformation speed controls the dynamics, leading to a wrinkle wavelength significantly smaller than that selected under quasistatic compression. Once active compression ceases, the wrinkles coarsen until their wavelength relaxes toward the equilibrium value. We develop a theoretical model coupling Stokes flow in the liquid to elastic bending of the sheet, which quantitatively predicts both the initial wavelength selection and its subsequent coarsening. We demonstrate that the same mechanism governs two dimensional and axisymmetric geometries, thereby extending classical static wavelength selection laws to dynamic situations. Although developed from controlled laboratory experiments, the model captures a generic viscous-elastic coupling and applies broadly to thin elastic films interacting with viscous environments, including the formation of surface wrinkles in pahoehoe lava flows.

cond-mat.soft↗

arXiv2024

Algebraic depletion interactions in two-temperature mixtures

The phase separation that occurs in two-temperature mixtures, which are driven out of equilibrium at the local scale, has been thoroughly characterized, but much less is known about the depletion interactions that drive it. Using numerical simulations in dimension 2, we show that the depletion interactions extend beyond two particle diameters in dilute systems, as expected at equilibrium, and decay algebraically with an exponent $-4$. Solving for the $N$-particle distribution function in the stationary state, perturbatively in the interaction potential, we show that algebraic correlations with an exponent $-2d$ arise from triplets of particles at different temperatures in spatial dimension $d$. Finally, simulations allow us to extend our results beyond the perturbative limit.

cond-mat.stat-mech↗

arXiv2022

Microscopic foundation of the $\mu$(I) rheology for dense granular flows on inclined planes

Macroscopic and microscopic properties of dense granular layers flowing down inclined planes are obtained from Discrete-Element-Method simulations for both frictionless and frictional grains. Three fundamental observations for dense granular flows are recovered, namely the occurrence of a critical stress, the Bagnold velocity profile, as well as well-defined friction and dilatancy laws. The microscopic aspects of the grain motion highlight the formation of transient clusters. From this microscopic picture, we derive a theoretical scaling model without any empirical input that explains quantitatively the fundamental laws of dense granular flows in incline plane and shear geometries. The adequacy between the model and the observed results suggests that granular flows can be viewed as flows from thermal fluids of hard spheres.

cond-mat.dis-nn↗

arXiv2019

A microscopic picture of erosion and sedimentation processes in dense granular flows

Gravity-driven flows of granular matter are involved in a wide variety of situations, ranging from industrial processes to geophysical phenomena, such as avalanches or landslides. These flows are characterized by the coexistence of solid and fluid phases, whose stability is directly related to the erosion and sedimentation occurring at the solid-fluid interface. To describe these mechanisms, we build a microscopic model involving friction, geometry, and a nonlocal cooperativity emerging from the propagation of collisions. This new picture enables us to obtain a detailed description of the exchanges between the fluid and solid phases. The model predicts a phase diagram including erosion, sedimentation, and stationary-flow regimes, in quantitative agreement with experiments and discrete-element-method simulations.

cond-mat.soft↗

arXiv2018

Cylinder morphology of a stretched and twisted ribbon

A rich zoology of shapes emerges from a simple stretched and twisted elastic ribbon. Despite a lot of interest, all these shape are not understood, in particular the shape that prevails at large tension and twist and that emerges from a transverse instability of the helicoid. Here, we propose a simple description for this cylindrical shape. By comparing its energy to the energy of other configurations, we are able to determine its location on the phase diagram. The theoretical predictions are in good agreement with our experimental results.

cond-mat.soft↗

arXiv2017

Emergent Strain-Stiffening in Interlocked Granular Chains

Granular chain packings exhibit a striking emergent strain-stiffening behavior despite the individual looseness of the constitutive chains. Using indentation experiments on such assemblies, we measure an exponential increase in the collective resistance force $F$ with the indentation depth $z$, and with the square root of the number $\mathcal{N}$ of beads per chain. These two observations are respectively reminiscent of the self-amplification of friction in a capstan or in interleaved books, as well as the physics of polymers. The experimental data are well captured by a novel model based on these two ingredients. Specifically, the resistance force is found to vary according to the universal relation: $\log F \sim \mu \sqrt{\mathcal{N}} \Phi^{11/8}z/ b $, where $\mu$ is the friction coefficient between two elementary beads, $b$ is their size, and $\Phi$ is the volume fraction of chain beads when semi-diluted in a surrounding medium of unconnected beads. Our study suggests that theories normally confined to the realm of polymer physics at a molecular level can be used to explain phenomena at a macroscopic level. This class of systems enables the study of friction in complex assemblies, with practical implications for the design of new materials, the textile industry, and biology.

cond-mat.soft↗

arXiv2016

From cylindrical to stretching ridges and wrinkles in twisted ribbons

Twisted ribbons subjected to a tension exhibit a remarkably rich morphology, from smooth and wrinkled helicoids, to cylindrical or faceted patterns. These shapes are intimately related to the instability of the natural, helicoidal symmetry of the system, which generates both longitudinal and transverse stresses, thereby leading to buckling of the ribbon. In this paper, we focus on the tessellation patterns made of triangular facets. Our experimental observations are described within an "asymptotic isometry" approach that brings together geometry and elasticity. The geometry consists of parametrized families of surfaces, isometric to the undeformed ribbon in the singular limit of vanishing thickness and tensile load. The energy, whose minimization selects the favored structure among those families, is governed by the tensile work and bending cost of the pattern. This framework describes the coexistence lines in a morphological phase diagram, and determines the domain of existence of faceted structures.

cond-mat.soft↗

arXiv2014

Dynamics of the prey prehension by chameleons through viscous adhesion: A multidisciplinary approach

Chameleons are able to capture very large preys by projecting the tongue and retracting it once it is in contact with preys. A strong adhesion between the tongue tip and the prey is therefore required during the retraction phase to ensure a successful capture. To determine the mechanism responsible for this strong bond, the viscosity of the mucus produced at the chameleon's tongue pad is measured by using the viscous drag exerted on rolling beads by a thin layer of mucus. The viscosity of this secretion is found to be about 400 times larger than the one of human saliva. With a dynamical model for viscous adhesion describing the motion of the compliant tongue and of the prey during the retraction phase, the evolution of the maximum prey size with respect to the chameleon body length is derived. This evolution is successfully compared with in vivo observations for various chameleon species and shows that the size of the captured preys is not limited by viscous adhesion thanks to the high mucus viscosity and the large contact area between the prey and the tongue.

physics.bio-ph↗

arXiv2011

How Geometry Controls the Tearing of Adhesive Thin Films on Curved Surfaces

Flaps can be detached from a thin film glued on a solid substrate by tearing and peeling. For flat substrates, it has been shown that these flaps spontaneously narrow and collapse in pointy triangular shapes. Here we show that various shapes, triangular, elliptic, acuminate or spatulate, can be observed for the tears by adjusting the curvature of the substrate. From combined experiments and theoretical models, we show that the flap morphology is governed by simple geometric rules.

cond-mat.soft↗

arXiv2011

Wrinkling hierarchy in constrained thin sheets from suspended graphene to curtains

We show that thin sheets under boundary confinement spontaneously generate a universal self-similar hierarchy of wrinkles. From simple geometry arguments and energy scalings, we develop a formalism based on wrinklons, the transition zone in the merging of two wrinkles, as building-blocks of the global pattern. Contrary to the case of crumple paper where elastic energy is focused, this transition is described as smooth in agreement with a recent numerical work. This formalism is validated from hundreds of nm for graphene sheets to meters for ordinary curtains, which shows the universality of our description. We finally describe the effect of an external tension to the distribution of the wrinkles.

cond-mat.mtrl-sci↗

arXiv2010

Multiple-length-scale elastic instability mimics parametric resonance of nonlinear oscillators

Spatially confined rigid membranes reorganize their morphology in response to the imposed constraints. A crumpled elastic sheet presents a complex pattern of random folds focusing the deformation energy while compressing a membrane resting on a soft foundation creates a regular pattern of sinusoidal wrinkles with a broad distribution of energy. Here, we study the energy distribution for highly confined membranes and show the emergence of a new morphological instability triggered by a period-doubling bifurcation. A periodic self-organized focalization of the deformation energy is observed provided an up-down symmetry breaking, induced by the intrinsic nonlinearity of the elasticity equations, occurs. The physical model, exhibiting an analogy with parametric resonance in nonlinear oscillator, is a new theoretical toolkit to understand the morphology of various confined systems, such as coated materials or living tissues, e.g., wrinkled skin, internal structure of lungs, internal elastica of an artery, brain convolutions or formation of fingerprints. Moreover, it opens the way to new kind of microfabrication design of multiperiodic or chaotic (aperiodic) surface topography via self-organization.

cond-mat.mtrl-sci↗

arXiv2009

Influence of Chain Interdiffusion Between Immiscible Polymers on Dewetting Dynamics

The interface between two immiscible polymers, polystyrene (PS) and polydimethylsiloxane (PDMS), was studied by neutron reflectivity and dewetting by using free PS chains and PDMS brushes. Unexpectedly, we found that the PS chains diffuse in the PDMS brushes at temperatures well below the glass transition temperatures of PS, the dynamics being largely determined by the grafting density of the brush. By this study, we demonstrate the major influence of the chains interdiffusion on the friction properties for a couple of immiscible polymers. By the way, the puzzling ageing of PS thin films observed from dewetting experiments is found to be directly related to modifications of the PS/PDMS interface.

cond-mat.soft↗

arXiv2007

Slippery or sticky ! Control of wrinkling patterns by selective adhesion

Wrinkling patterns at the metallized surface of thin polymer films are shown to be sensitive to the sticky or slippery character of the polymer/substrate interface (titanium coating, polystyrene film and coated silicon substrate). Selective prefered wrinkle orientation and amplitude are achieved. Existing theoretical models are expanded to specific boundary conditions (adhesive vs slippery) and rationalize these observations.

cond-mat.soft↗

arXiv2005

The Role of Nonlinear Friction in the Dewetting of Thin Film Polymers

The study of the dewetting of very thin polymer films has recently revealed many unexpected features (e.g. unusual rim morphologies and front velocities) which have been the focus of several theoretical models. Surprisingly, the most striking feature of all, that is a decrease of the rim width with time, have not yet been explained. In the present letter, we show how the combined effects of a non-linear friction between the film and the substrate, and the presence of residual stresses within the film, result in the presence of a maximum in the time evolution of the rim width. In addition, we show how the introduction of a non-linear friction can also simply explain the rapid decrease of the dewetting velocity with time observed experimentally.

cond-mat.soft↗