ESPCI web site
Séminaires
Le séminaire hebdomadaire du laboratoire PMMH a lieu tous les vendredis à 11h, au premier étage Barre Cassan, campus Jussieu (plan).
Alice Pelosse
Stéphane Perrard
Etienne Reyssat
Virgile Thiévenaz
PMMH
BARRE CASSAN
BAT A 1ER ETAGE CASE 18
7 QUAI SAINT BERNARD
75005 PARIS
France
Tel : (33) 1 40 79 45 22
Séminaire PMMH – Scott Waitukaitis (IST Austria)
Le Lapin Électrostatique : Static Electricity is an Unpredictable Little Bunny
"Static electricity" defies our best attempts to make sense of it. More scientifically referred to as contact electrification (CE), the effect seems straightforward—touch two neutral materials together, separate them, and they will have exchanged some electrical charge. Simple as this sounds, the effect is plagued by unpredictability, and we don't even know what is transferred (e.g., ions vs. electrons), let alone why. In my group, we focus on CE between "identical" materials, which, though counterintuitive, has long been known to occur. I will discuss two sets of experiments on this same-material CE, which are helping us tame the unpredictability and get closer to the mechanism. In the first, we use acoustic levitation to study the charging of an SiO2 sphere as it bounces on an SiO2 plate. We test a leading hypothesis for same-material CE, i.e., that it is due to local variability in surface properties, and show that this is not the case. Going further, we reveal that there is a critical dependence on sample history, especially RH exposure, temperature, and surface treatment, which points to a key role played by surface adsorbates. In the second experiment, we study the charge exchange between soft polymers—identically prepared samples of PDMS. Measuring the charge exchange for all pair combinations of an ensemble, we find they begin charging randomly, but over time evolve into a triboelectric series—i.e., a transitive ordering based on the polarity of the charge acquired. We find that this is caused by the act of contact itself ; samples that have experienced more contacts in their history charge negatively to ones that have experienced less. Based on this observation, we develop a model that explains why our materials evolve into a series, and going further leverage it to control the charging behavior. Ultimately, we discover that this memory effect is due to nanoscale changes in surface morphology, pointing to a mechanism intimately coupled with tribology and contact mechanics.
Séminaires (4)
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Séminaire PMMH — Constantino Tsallis (Centro Brasileiro de Pesquisas Fisicas)
Vendredi 6 novembre de 11h00 à 12h00 - Salle réunion PMMH 1
Nonadditive entropies : Along the Boltzmann-Gibbs legacy
The magnificent Boltzmann-Gibbs (BG) statistical mechanics is grounded on the celebrated additive entropic functional S_BG. This theory satisfactorily describes a plethora of so-called simple systems. It fails, however, for wide classes of natural, technological and social complex systems. The violation of the (…) -
Séminaire PMMH Nicolas Bain (Institut Lumière Matière, Lyon)
Vendredi 13 novembre de 11h00 à 12h00 - Salle réunion PMMH 1
3D Micromechanics, from interfacial mechanics to transport properties
In recent years, 3D micromechanics has emerged as a powerful tool to quantify and understand mechanical behaviors of soft materials, from fracture, to freezing, and interfacial mechanics. In this presentation, I will illustrate the principle and potential of this technique by detailing a recent project on the (…) -
Séminaire PMMH - Ada Altieri (MSC, Paris)
Vendredi 20 novembre de 11h00 à 12h00 - Salle réunion PMMH 1
From disordered Generalized Lotka-Volterra models to gut microbiome complexity
Inferring species interactions in highly heterogeneous ecological communities and developing a robust, predictive theory of ecological stability remain major challenges, due both to the amount of data required and the complexity of the underlying interaction network. In this talk, I will present a high-dimensional (…) -
Séminaire PMMH — Benjamin Apffel (ENS Lyon)
Vendredi 8 janvier 2027 de 11h00 à 12h00 - Salle réunion PMMH 1
Computing with Frustrated Space-Time Metamaterials
Space-time metamaterials are engineered media whose constitutive parameters are modulated simultaneously in both space and time. They are now used to achieve unprecedented wave control. However, the vast majority of studies operate in the stable regime, where modulation parameters are chosen to ensure linear wave (…)
Instructions générales pour les conférenciers
Le public du séminaire est très hétérogène (rien qu’au PMMH nous travaillons sur des thématiques très diverses, mécanique des fluides, des milieux granulaires, des solides, physique statistique, physique du mouillage, micro-fluidique, biophysique,...) l’objectif est donc de ne pas faire un séminaire trop spécialiste : au moins la première moitié du séminaire à un niveau accessible pour celui qui ne connaît rien sur le sujet.
Le séminaire a lieu à 11h. rendez-vous 15 minutes avant pour installer et tester la projection.
Le séminaire dure environ 45 minutes pour laisser un peu de temps pour discuter à la fin.
- Séminaires ESPCI-ENS de biophysique
- Séminaires du Département de Physique de l’ENS
- Séminaires du Laboratoire d’Hydrodynamique de l’X
- Séminaire de Mécanique d’Orsay (page web FAST)
- Séminaire de Mécanique d’Orsay (page web LIMSI)
- Séminaire de Mécanique des Fluides de l’Institut Jean le Rond d’Alembert
- Séminaires du laboratoire MSC, Paris VII
- Séminaires Gulliver
Soutenances de thèse
Auriane Huyghues-Despointes : 22/09 - 14h30
Sébastien Kuchly : 23/09 - 14h
Juliette Michaud : 28/09 - 14h
Diane Komaroff : 02/10 - 14h
Marc Vacher : 13/10
Jules Tampier : 16/10 - 13h30
Alex Le Guen : 01/12 - 14h
Elias Lundheim : 07/12 - 9H
Séminaires café (internes, tous les jeudis)
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