Transport of two-phase fluids in microfluidics devices
Contacts : Pascal Panizza, Laurent Courbin
Flows of deformable objects in microfluidics networks or porous media are ubiquitous in nature as well as in industry. Illustrative examples include blood circulation, flows of foams and emulsions through porous rocks for enhanced oil recovery and transport of droplets used in digital microfluidics applications. Because of time-delayed feedbacks resulting from non-linear couplings between the flow and the structure of these fluids, these systems exhibit complex dynamics, also observed in traffic flows and in cellular automata . We study the complex dynamics of droplet traffic, the nonlinear cooperative droplet break-ups  resulting from object-to-object hydrodynamic interaction in confined ducts and the emergence of commensurability-driven structural defects in double emulsions produced with microfluidics .
- D. A. Sessoms, A. Amon, L. Courbin, et P. Panizza, Phys. Rev. Lett. 105, 154501 (2010), Complex dynamics of droplet trafic at a bifurcating path: Periodicity, multistability, and selection rules.
- A. Schmit, L. Salkin, L. Courbin, et P. Panizza, Soft Matter 11, 2454 (2015), Cooperative breakups induced by drop-to-drop interactions in one-dimensional flows of drops against micro-obstacles.
- A. Schmit, L. Salkin, L. Courbin, et P. Panizza, Soft Matter 10, 4743 (2014),Commensurability-driven structural defects in double emulsions produced with two-step microfluidic techniques.
Drying of complex fluids in porous media : towards hierarchical materials
Contacts : Laurent Courbin, Guillaume Raffy, Pascal Panizza, Franck Artzner
Understanding the evaporation of binary liquids or colloidal dispersions in porous media is important for many disciplines, e.g., soil physics and civil engineering and diverse processes such as the underground sequestration of CO2. The key issue in most cases is to grasp the creation, locus and morphology of the solid deposits formed during drying. For instance, this topic is crucial in civil engineering as salt weathering can cause severe damage to the built environmental and in material science because evaporation can serve as a new route to design smart materials. Yet, the development of models for drying in porous media and the proper description of the formation of deposits in such media are generally challenging tasks. We address this issue by study the evaporation of model binary systems such as surfactant solutions or colloidal dispersions, within transparent 2D porous media fabricated by soft lithography techniques . As a fluid evaporates in such a device, labyrinthine patterns connecting adjacent posts form at the pore scale. As drying ends, these monodisperse ``walls" made of solid deposits compose a centimeter-sized structure that resembles a maze. We study the mechanism of formation of these structures at the pore scale and we develop numerical approaches based on cellular automaton to rationalize our results at the network scale .
Labyrinthine drying patterns
The design of hierarchical materials can be achieved by reducing the volume fraction of colloidal suspensions . The control of morphologies, sphere or rods, allows one to generate an abundant diversity of organizations at the nanometer scale. The use of reduction in volume as a control parameter offers the opportunity to control the morphology at the millimeter scale using microstructured surfaces. Indeed, the shaping of fluid-fluid interfaces is a direct macroscopic consequence of the unit-cell of the microtexture.
4] C. Hamon, M. Postic, E. Mazari, T. Bizien, C. Dupuis, P. Even-Hernandez, A. Jimenez, L. Courbin, C. Gosse, F. Artzner, et V. Marchi-Artzner, ACS Nano 6, 4137 (2012), Three-Dimensional Self-Assembling of Gold Nanorods with Controlled Macroscopic Shape and Local Smectic B Order.
5] P. Panizza, H. Algaba, M. Postic, G. Raffy, L. Courbin, and F. Artzner, submitted (2018), Order-disorder structural transitions in mazes built by evaporating drops.
6] T. Bizien, P. Even-Hernandez, M. Postic, E. Mazari, S. Chevance, A. Bondon, C. Hamon, D. Troadec, L. Largeau, C. Dupuis, C. Gosse, F. Artzner and V. Marchi, Small, 2014, 10(18), 3707–3716, Peptidic Ligands to Control the Three-Dimensional Self-Assembly of Quantum Rods in Aqueous Media.
Order and disorder in bone cancer
Contacts : Franck Artzner, Cristelle Mériadec
Osteosarcomas and Ewing sarcomas are the most frequent malignant primary bone tumours, arising near the growth plates in adolescents. However, the mechanical regulation of tumour growth by bone tissue which may be implicated in the pathogenesis of these tumours has never been explored.
To this end, we explore the early stages of the tumour invasion in a synergic model of mouse osteosarcoma. The first results show abnormal overproduction of bone, followed by a deterioration then leading to tumour invasion. These observations lead us to the hypothesis that the rapid development of the bone structures is facilitated by their mechanical properties. Their degradation then frees space for tumour invasion, which can naturally invade the tissues in the place of other cells without any mechanical effort.
Contacts : Franck Artzner, Cristelle Mériadec
The structural control over length scale decades of self-assemblies requires coupling between molecular interactions and macroscopic gradients. In the past, we succeeded in constructing centimeter long silica nanotubes having a sub-angstrom wall thickness precision . We learnt that two properties are required for such coupling: (i) a gradient of chemical potential and (ii) a feedback mechanism.
The understanding of the nanotube assembly of octapeptide, the Lanreotide has been achieved by a depth study of the intermediate steps of the assembly and the exact location of the condensed counter-ions in the wall of the tubes. This offers the opportunity to tune the wall thickness of the nanotubes. The diameter of the nanotubes can be fixed between 9 and 35 nm by varying the size of a single residue . Another molecule exhibits nanotubes whose diameter is determined by the pH, 11 nm at low pH and 50 nm at high pH. Both structures were solved at the atomic scale. They show a large conformational change induced by deprotonation of a single histidine .
7] E. Pouget, E. Dujardin, A. Cavalier, A. Moreac, C. Valéry, V. Marchi-Artzner, T. Weiss, A. Renault, M. Paternostre, F. Artzner, Nature Materials, 2007, 6, 434-439, Hierarchical architectures by synergy between dynamical template self-assembly and biomineralization.
8] C. Tarabout , S. Roux , F. Gobeaux , N. Fay, E. Pouget , C. Meriadec , M. Ligeti , D. Thomas , M. IJsselstijn , F. Besselievre , D. Buisson , J.-M. Verbavatz , M. Petitjean , C. Valéry , L. Perrin , B. Rousseau , F. Artzner, M. Paternostre, J.-C. Cintrat, Proc. Natl. Acad. Sci. USA, 2011, 108 (19) 7679-7684, Chemical control of peptide nanotube diameter: a strategy based on the structure of the nanotube.
9] C. Valéry, S. Deville-Foillard, C. Lefebvre, N. Taberner, P. Legrand, F. Meneau, C. Meriadec, C. Delvaux, T. Bizien, E. Kasotakis, C. Lopez-Iglesias, A. Gall, S. Bressanelli, M.-H. Le Du, M. Paternostre, F. Artzner, Nature Communications, 2015, 6(7771), 1–8, Atomic view of the Histidine environment stabilizing higher pH conformations of pH-dependent proteins.