. .. Droplet, 143 5.5.1 Elongated droplet in a straight capillary

.. .. Conclusion,

, Swimming together in 1D 159

, 159 Brief introduction to phase transition in 1D

.. .. Context,

. .. Development, 179 6.2.2 Numerical implementation of the model

.. .. Conclusion,

.. .. Conclusion, , p.219

, Résumé en Français 235

. .. , 235 7.4.1 Nager, un enjeux biologique et physique

. .. Travaux, , p.239

2. .. Nage-en,

1. .. Nage-en,

.. .. Conclusion-générale,

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, Il est construit de la même manière que le manuscrit de thèse, en deux parties constituées respectivement de trois et quatre chapitres. La première partie se veut pédagogique et présente les bases théoriques et expérimentale de ce travail. La deuxième partie rassemble les résultats obtenus tout au long de la thèse sur les axes de recherche suivants: la nage en 2D

, Contextes experimental et théorique

, Ces chapitres introductifs ont pour but de présenter les enjeux de ce travail, mais aussi le systèmeétudié et les mécanismes physiques principaux qui vont nous intéresser

U. Nager,

, Les systèmes vivants présentent un certain nombre de points communs, qui sont jugésêtre les ingrédients indispensablesà la vie: la compartimentation, grandir et se diviser, traiter des informations

, Un des enjeux de la création de cellules artificielles est de regrouper tous ces ingrédients dans un seul système. L'une des techniques utilisée est la technique "de bas en haut", qui consisteà partir de systèmes physiques ou chimiques simples età les complexifier. En particulier, des systèmes de gouttes, trivialement compartimentées, ontété utilisés pour reproduire chacune des caractéristiques citées plus haut

, Le système auquel nous nous intéressons dans ce travail est une goutte active, qui va puiser de l'énergie dans son environnement pour produire des fluxà son interface et se propulser. Ce système présente donc trois des caractéristiques du vivant (compartimentation, transformation d'énergie et adaptation), ce qui font d'elles un système modèle simple particulièrement

, Un nageur est un objet qui induit lui-même ces conditions aux limites pour produire un mouvement. Le nageur doit alors briser la symétrie isotrope pour partir dans une direction privilégiée. Cette brisure de symétrie peutêtre géométrique (cas des particules de Janus), ou résulter d'une instabilité (cas des gouttes nageuses). Il est important de noter que dans ce dernier cas

, Dans le cas d'une goutte nageuse,à cause du couplage entre l'hydrodynamique et les conditions aux limites, cette influence a de grandes chances d'influer sur l'activité du nageur, et donc de modifier effectivement sa nage

, Nage de gouttes d'eau pure: (a) trajectoires d'une cinquantaine de gouttes d'eau de rayon ? 50 µm dans une chambre d'observation de 1 cm remplie d'une solution de 25mM de mono-oleine dans du squalane, d'une durée de 500 s. Le code couleur représente le temps. (b) Vitesse et (c) diamètre des gouttes au cours du temps pour une sélection de huit trajectoires, La nage de ces gouttes est Figure 7.13: Figures de, vol.87

, champs de concentration, modifient le nageur lui même. Chapitre 7.5.1, nous avons vu que la présence d'un mur changeait le comportement longue portée des gouttes

, empêchait pas les gouttes de nager, mais modifie leurs formes ce qui mèneà des phénomènes complexes tels que des divisions spontanées. Chapitre 7.5.3, les interactions entre nageurs provoquent l'émergence d'effets collectifs tels que les trains ou les bouchons. Dans tous ces cas, ces contraintes extérieures qui n'auraient pu avoir comme effet que de gêner la nage, enrichissent grandement la phénoménologie du système. Au delà de la simple compréhension de toutes ces situations particulières, cesétudes donnent des clés de compréhension sur de nombreux phénomènesà l