The bronchial epithelium mucociliary function ensuring the lung continuous clearance relies on mucus rheological properties and cilia beating coordination. Our biophysical approach aims at understanding two points. First, the biochemical and physical parameters affecting the mucus viscoelastic properties and evaluating its use as a marker for the diagnosis of respiratory diseases. Secondly the cilia coordination and its coupling with the mucus.We performed rheological experiments on mucus extracted from Air Liquid Interface (ALI) cultures of bronchial epithelium reconstituted from bronchial biopsies. Our approach consists in combining standard macro-rheology to micro-rheology performed with optical tweezers, in order to quantify the mucus flowing behavior at different scales, from the cilia up to the mucus layer length scales.Macro- and micro-rheology give different results. At the macro-scale, we obtain an elastic plateau (1 to 2 Pa), a shear-thinning behaviour and a very low yield stress (0.05-0.2 Pa). While at the micro-scale, we obtain a viscous flow, with a very low viscoelastic modulus (10-3-10-2 Pa). Nevertheless, by applying local forces at the interfaces, we observe an important adhesion and elasticity. Mucus adhesion should be taken into account to understand the differences between these different length scales and more generally to characterize the mucus properties. We also perform original experiments using optical tweezers directly on the epithelium, to access the viscoelastic response in the various mucus layers. We obtain an increased elasticity in the vicinity to the epithelium. Moreover, comparison of physical properties of mucus from the culture and directly extracted from patient lungs, provides an additional validation of the ALI model.Finally, the specific methodology we developed to quantify cilia activity and coordination, allows us to map, the cilia spatial distribution, the beating frequency and orientation of each cilium, and their standard deviation within a cilia cluster (cell). Local quantification of the cilia activity coupled to the measurement of the mucus velocity field, should help to evaluate the efficiency of the mucociliary function and to understand the mechanisms of clearance.

The mucociliary function of the bronchial epithelium ensures the continuous clearance of the respiratory system. This function relies on two main elements: mucus and cilia beating. We perform here a rheological characterization of mucus samples extracted from ALI (Air-liquid interface) cultures of bronchial epithelium. Our approach combines macro- and micro-rheology techniques with the aim of quantifying the mucus viscoelastic properties at different length scales (from the size of bronchial cilia up to the scale on which mucus is transported). In addition, this methodology allows us to compare the rheological behavior of mucus samples corresponding to different pathologies.

The mucociliary function of the bronchial epithelium ensures the continuous clearance of the respiratory system. This function relies on two main elements: the mucus properties and the cilia beating coordination. First, we perform a rheological characterization of mucus samples extracted from ALI (Air-liquid interface) cultures of bronchial epithelium. Our approach combines macro- and micro-rheology techniques with the aim of quantifying the mucus viscoelastic properties at different length scales (from the size of bronchial cilia up to the scale on which mucus is transported). Secondly, we analyze the ciliary activity of these epithelia of ALI cultures by images processing and data analysis on videomicroscopies of the epithelium. These methodologies allow us to understand the coupling between the mucus and the cilia coordination and to compare samples corresponding to different pathologies.

Despite being by far among the most widespread interface on Earth, with a pervasive presence in environment, biology, industry and daily life, physical phenomena at Air-Water Interface (AWI) are still largely elusive. This fact is related to the complexity of AWI with its peculiar electrostatic and flow boundary conditions. In this paper, we present a study of the dynamics and interactions of charged microparticles diffusing at submicrometric distances from an AWI. An interferometric set-up mounted on a microscope gives access to an highly resolved trajectory of the colloid (5-10 nm). Contrary to other established techniques (like TIRM and holography) our technique has the great advantage of allowing the measure of the absolute particle-interface distance. In order to control the electrostatic we use different concentration of salt and different pH in association with pH dependent charged microparticles.Surprisingly new equilibrium distances from the AWI are measured not accounted by established theories. In addition different drags corresponding to different boundaries conditions are found for same combination of particle and AWI depending on the particle’s motion direction namely perpendicular or parallel to the AWI.

The confinement of colloidal particles in thin liquid films is typically accompanied with interfacial deformations which give rise to long-range capillary forces, attractive in most of the cases [1]. In simple fluids, these long-range capillary forces compete mostly with the isotropic electrostatic interactions. In nematic[2] or smectic[3] liquid crystal free films, other long-range anisotropic interactions related to bulk distortions of the surrounding fluid appear and new equilibrium positions or the possibility of forming new types of 2D colloidal assemblies appear via original elasto-capillarity couplings.In a previous work [4], using spatially resolved retardation and easy-axis maps, we have analysed quantitatively the 2D interfaces deformation and the nematic textures observed around isolated particles (see Fig.1) embedded in thin nematic films with hybrid anchoring conditions. Using numerical methods, we have explained quantitatively the different textures and the formation of topological defects. Contrary to what is classically observed in aligned nematic cells, the equilibrium patterns (such as the elastic dipole) due to a microsphere can be much larger than the particle size (as shown in Fig.1). Here we have focused on the overall colloidal interactions and the equilibrium positions between spherical or anisotropic particles. We have experimentally characterized the equilibrium configuration of isolated colloidal pairs. Using a 2D model of the nematic elasticity and finite element approaches, we have also numerically characterized the pair interaction and explained the textures observed. These new spontaneous organizations in thin nematic films offer new ways to self-assemble complex colloidal systems in 2D.References[1] P.A. Kralchevsky, K. Nagayama, Adv Colloid Interface Sci , 85, 145 (2000).[2] H.Jeridi, M.A.Gharbi, T.Othman, Ch.Blanc, Proc Natl Acad Sci USA, 112, 14771(2015).[3] M.A.Gharbi et al., Langmuir, 34, 2006 (2018).[4] H. Jeridi, M. Tasinkevych, T. Othman, and Ch. Blanc, Langmuir, 32, 9097 (2016).

Aqueous dispersions of graphene-derived monolayers form liquid crystal at rather low concentrations due to the high aspect ratio of these flakes [1,2]. If graphene oxide dispersions are easily obtained in water, reduced graphene oxide necessitates the use of surfactants [3]. Preparing organized materials and thin films from these dispersions then requires a good control of the liquid crystal ordering during the deposition and the drying of the films.The flakes easily align at high shear [4,5], which has allowed us to complete previous optical characterizations of the various graphene layers (birefringence and linear dichroism). However at low shear or under small dispalcements, thin films often show peculiar patterns (such as the periodic textures shown in Fig.1). We have shown how to create and stabilize large-sized periodic textures. The patterns have been characterized under optical and electronic microscopies. Their stability can be explained by the competition between the anchoring field of the substrate and the presence of a yield stress resulting from the peculiar elastic and rheological properties of the graphene oxide liquid crystals. Our results also clarify why long-standing hypotheses on the presence of exotic phases [1] at large concentrations are present in the literature.References[1] Z. Xu, C. Gao Nat Commun., 2, 571 (2011).[2] C. Zakri et al., Phil. Trans. A, 371, 20120499 (2013).[3] C. Zamora et al, J. Phys. Chem. Lett. 3, 2425 (2012).[4] P. Poulin et al, Proc Natl Acad Sci USA, 113, 11088 (2016).[5] S-H Honga, T.Z. Shena and J. K. Songa, Liquid Crystals, 42, 261 (2015)

Thin and ultrathin metal coatings are increasingly required by the electronics and optics industries onall types of substrates. However, the adhesion of noble metals is very poor on non-metallic substrates like glass,other oxide materials and polymers. By contrast, CVD graphene has a strong adhesion energy (~0.31-0.45 J.m-2depending on the number of layers) on glass [1]. On the other hand, graphene oxide (GO) was recently shown topromote adhesion of ZnO nanoparticles and subsequent ZnO films on glass or silicon substrates [2].In this work we use GO/Au nanoparticles (NP) composite thin films as bifunctional materials to bothpromote adhesion on glass and assist the deposition of copper in electroless wet industrial coating processes. Wediscuss the influence of the NP density, surface treatment and deposition parameters on the homogeneity andadhesion of the GO/Au NP and copper layers.[1] S. P. Koenig, N. G. Boddeti, M. L. Dunn, and J. S. Bunch, 2011, Nat. Nano. 6, 543‑546[2] Q. Ma, X. Zhu, D. Zhang, and S. Liu, 2014, J. Mater. Chem. C 22, 8956‑8961