References of "Vandewalle, Nicolas"
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See detailSelf-assembly of capillary multipoles
Poty, Martin ULiege; Lagubeau, Guillaume; Lumay, Geoffroy ULiege et al

Conference (2016, July 21)

Self-assembly of floating particles driven by capillary forces at some liquid-air interface leads to the formation of two-dimensionnal structures. Using a 3d printer, millimeter scale objets are produced ... [more ▼]

Self-assembly of floating particles driven by capillary forces at some liquid-air interface leads to the formation of two-dimensionnal structures. Using a 3d printer, millimeter scale objets are produced. Their 3d shape is chosen in order to create capillary multipoles. The capillary interactions between these components can be either attractive or repulsive depending on the interface local deformations along the liquid-air interface. In order to understand how the shape of an object deforms the interface, we developed an original profilometry method. The measurements show that specific structures can be programmed by selecting the 3d branched shapes. [less ▲]

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See detailDroplet manipulation on fiber networks
Weyer, Floriane ULiege; Pan, Zhao; Truscott, Tadd et al

Poster (2016, July)

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See detailMagnetocapillary self-assemblies: Swimming and micromanipulation
Grosjean, Galien ULiege; Hubert, Maxime ULiege; Lagubeau, Guillaume et al

Poster (2016, July)

Floating magnetic particles can self-assemble into structures, by a combination of a magnetic dipole-dipole interaction and an attraction due to the interfacial deformation. These structures are ... [more ▼]

Floating magnetic particles can self-assemble into structures, by a combination of a magnetic dipole-dipole interaction and an attraction due to the interfacial deformation. These structures are periodically deformed in a non reciprocal way using magnetic fields, which leads to controllable low Reynolds number locomotion. Such microswimmers provide a basis for micromanipulation applications such as transport of micro-objects, local mixing of fluids or surface cleaning. [less ▲]

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See detailWaveguides for walking droplets
Filoux, Boris ULiege; Hubert, Maxime ULiege; Schlagheck, Peter ULiege et al

E-print/Working paper (2016)

When gently placing a droplet onto a vertically vibrated bath, a drop can bounce without coalescing. Upon increasing the forcing acceleration, the droplet is propelled by the wave it generates and becomes ... [more ▼]

When gently placing a droplet onto a vertically vibrated bath, a drop can bounce without coalescing. Upon increasing the forcing acceleration, the droplet is propelled by the wave it generates and becomes a walker with a well defined speed. We investigate the confinement of a walker in different rectangular cavities, used as waveguides for the Faraday waves emitted by successive droplet bounces. By studying the walker velocities, we discover that 1d confinement is optimal for narrow channels of width of D≃1.5λF. We also propose an analogy with waveguide models based on the observation of the Faraday instability within the channels. [less ▲]

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See detailOn the coarsening dynamics of a granular lattice gas
Opsomer, Eric ULiege; Noirhomme, Martial ULiege; Ludewig, François et al

in European Physical Journal E -- Soft Matter (2016)

We investigated experimentally and theoretically the dynamics of a driven granular gas on a square lattice and discovered two characteristic regimes: Initially, given the dissipative nature of the ... [more ▼]

We investigated experimentally and theoretically the dynamics of a driven granular gas on a square lattice and discovered two characteristic regimes: Initially, given the dissipative nature of the collisions, particles move erratically through the system and start to gather on selected sites called traps. Later on, the formation of those traps leads to a strong decrease of the grain mobility and slows down dramatically the dynamics of the entire system. We realize detailed measurements linking a trap’s stability to the global evolution of the system and propose a model reproducing the entire dynamics of the system. Our work emphasizes the complexity of coarsening dynamics of dilute granular systems. [less ▲]

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See detailStatics and dynamics of magnetocapillary bonds
Lagubeau, Guillaume; Grosjean, Galien ULiege; Darras, Alexis ULiege et al

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2016), 93

When ferromagnetic particles are suspended at an interface under magnetic fields, dipole-dipole interactions compete with capillary attraction. This combination of forces has recently given promising ... [more ▼]

When ferromagnetic particles are suspended at an interface under magnetic fields, dipole-dipole interactions compete with capillary attraction. This combination of forces has recently given promising results towards controllable self-assemblies as well as low-Reynolds-number swimming systems. The elementary unit of these assemblies is a pair of particles. Although equilibrium properties of this interaction are well described, the dynamics remain unclear. In this paper, the properties of magnetocapillary bonds are determined by probing them with magnetic perturbations. Two deformation modes are evidenced and discussed. These modes exhibit resonances whose frequencies can be detuned to generate nonreciprocal motion. A model is proposed that can become the basis for elaborate collective behaviors. [less ▲]

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See detailScattering theory of walking droplets in the presence of obstacles
Dubertrand, Rémy ULiege; Hubert, Maxime ULiege; Schlagheck, Peter ULiege et al

in New Journal of Physics (2016), 18

We aim to describe a droplet bouncing on a vibrating bath using a simple and highly versatile model inspired from quantum mechanics. Close to the Faraday instability, a long-lived surface wave is created ... [more ▼]

We aim to describe a droplet bouncing on a vibrating bath using a simple and highly versatile model inspired from quantum mechanics. Close to the Faraday instability, a long-lived surface wave is created at each bounce, which serves as a pilot wave for the droplet. This leads to so called walking droplets or walkers. Since the seminal experiment by {\it Couder et al} [Phys. Rev. Lett. {\bf 97}, 154101 (2006)] there have been many attempts to accurately reproduce the experimental results. We propose to describe the trajectories of a walker using a Green function approach. The Green function is related to the Helmholtz equation with Neumann boundary conditions on the obstacle(s) and outgoing boundary conditions at infinity. For a single-slit geometry our model is exactly solvable and reproduces some general features observed experimentally. It stands for a promising candidate to account for the presence of arbitrary boundaries in the walker's dynamics. [less ▲]

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See detailRibbons of superparamagnetic colloids in magnetic field
Darras, Alexis ULiege; Fiscina, Jorge; Pakpour, Maryam et al

in European Journal of Physics (2016), 39(47),

While the aggregation process of superparamagnetic colloids in strong magnetic field is well known on short time since a few decades, recent theoretical works predicted an equilibrium state reached after ... [more ▼]

While the aggregation process of superparamagnetic colloids in strong magnetic field is well known on short time since a few decades, recent theoretical works predicted an equilibrium state reached after a long time. In the present paper, we present experimental observations of this equilibrium state with a two-dimensional system and we compare our data with the predictions of a pre-existing model. Above a critical aggregation size, a deviation between the model and the experimental data is observed. This deviation is explained by the formation of ribbon-shaped aggregates. The ribbons are formed due to lateral aggregation of chains. An estimation of the magnetic energy for chains and ribbons shows that ribbons are stable structures when the number of magnetic grains is higher than N = 30. [less ▲]

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See detailFloating self-assembled microswimmers
Grosjean, Galien ULiege; Vandewalle, Nicolas ULiege; Hubert, Maxime ULiege et al

Conference (2016, January 28)

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See detailspontaneous rotation of an ice disk while melting on a solid plate
Dorbolo, Stéphane ULiege; Vandewalle, Nicolas ULiege; darbois-texier, baptiste

in Physics of Fluids (2016), 28

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See detailRotation of melting ice disks due to melt fluid flow
Dorbolo, Stéphane ULiege; adami, nicolas; Dubois, Charles ULiege et al

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2016)

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See detailDisplacement of an Electrically Charged Drop on a Vibrating Bath
Brandenbourger, Martin ULiege; Vandewalle, Nicolas ULiege; Dorbolo, Stéphane ULiege

in Physical Review Letters (2016), 116

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See detailRemote control of self-assembled microswimmers
Grosjean, Galien ULiege; Lagubeau, Guillaume ULiege; Darras, Alexis ULiege et al

in Scientific Reports (2015)

Floating magnetic particles can self-assemble into structures. These structures are periodically deformed in a non reciprocal way using magnetic fields, which leads to controllable low Reynolds number ... [more ▼]

Floating magnetic particles can self-assemble into structures. These structures are periodically deformed in a non reciprocal way using magnetic fields, which leads to controllable low Reynolds number locomotion. [less ▲]

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See detailClustering and segregation in a driven bi-disperse granular gas
Opsomer, Eric ULiege; Ludewig, François; Vandewalle, Nicolas ULiege

Conference (2015, September 24)

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See detailQuantitatively mimicking wet colloidal suspensions with dry granular media
Messina, René; Aljawhari, Sarah; Bécu, Lydiane et al

in Scientific Reports (2015)

Athermal two-dimensional granular systems are exposed to external mechanical noise leading to Brownian-like motion. Using tunable repulsive interparticle interaction, it is shown that the same ... [more ▼]

Athermal two-dimensional granular systems are exposed to external mechanical noise leading to Brownian-like motion. Using tunable repulsive interparticle interaction, it is shown that the same microstructure as that observed in colloidal suspensions can be quantitatively recovered at a macroscopic scale. To that end, experiments on granular and colloidal systems made up of magnetized particles as well as computer simulations are performed and compared. Excellent agreement throughout the range of the magnetic coupling parameter Γ is found for the pair distribution as well as the bond-orientational correlation functions. This finding opens new ways to efficiently and very conveniently explore phase transitions, crystallization, nucleation, etc in confined geometries. [less ▲]

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See detailComplex Magnetocapillary Microswimmers
Grosjean, Galien ULiege; Vandewalle, Nicolas ULiege; Lagubeau, Guillaume ULiege et al

Poster (2015, July)

When particles are suspended at air-water interfaces in the presence of a vertical magnetic field, dipole-dipole repulsion competes with capillary attraction. Magnetocapillary self-assemblies, composed of ... [more ▼]

When particles are suspended at air-water interfaces in the presence of a vertical magnetic field, dipole-dipole repulsion competes with capillary attraction. Magnetocapillary self-assemblies, composed of N soft-ferromagnetic beads, have been studied as a way to produce controllable micro swimmers at low Reynolds numbers. We hereby investigate the different dynamical behaviors obtained for various self-assemblies. The dynamic interaction of a pair of particles (N = 2) generates a rich behavior at the origin of a non-reciprocal motion, being the major physical ingredient for low Reynolds locomotion. By adding particles to this elementary system up to N = 8, we create new symmetries relevant to generate translational and rotational motions. We propose a model for describing the motion driven by an external field, being the basis for developing elaborated collective behaviors. [less ▲]

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See detailCompound droplet manipulations on fiber arrays
Weyer, Floriane ULiege; Lismont, Marjorie ULiege; Dreesen, Laurent ULiege et al

in Soft Matter (2015), 11

Recent works demonstrated that fiber arrays may constitute new means of designing open digital microfluidic systems. Various processes, such as droplet motion, fragmentation, trapping, release, mixing and ... [more ▼]

Recent works demonstrated that fiber arrays may constitute new means of designing open digital microfluidic systems. Various processes, such as droplet motion, fragmentation, trapping, release, mixing and encapsulation, may be achieved on fiber arrays. However, handling a large number of tiny droplets resulting from the mixing of several liquid components is required for developing microreactors, smart sensors or microemulsifying drugs. Here, we show that the manipulation of tiny droplets onto fiber networks allows for creating compound droplets with a high complexity level. Moreover, this cost-effective and adjustable method may also be implemented with optical fibers in order to develop fluorescence-based biosensor. [less ▲]

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See detailCompound Droplets on Fibers
Weyer, Floriane ULiege; Ben Said, Marouen; Hötzer, Johannes et al

in Langmuir (2015), 31(28), 77997805

Droplets on fibers have been extensively studied in the recent years. Although the equilibrium shapes of simple droplets on fibers are well established, the situation becomes more complex for compound ... [more ▼]

Droplets on fibers have been extensively studied in the recent years. Although the equilibrium shapes of simple droplets on fibers are well established, the situation becomes more complex for compound fluidic systems. Through experimental and numerical investigations, we show herein that compound droplets can be formed on fibers and that they adopt specific geometries. We focus on the various contact lines formed at the meeting of the different phases and we study their equilibrium state. It appears that, depending on the surface tensions, the triple contact lines can remain separate or merge together and form quadruple lines. The nature of the contact lines influences the behavior of the compound droplets on fibers. Indeed, both experimental and numerical results show that, during the detachment process, depending on whether the contact lines are triple or quadruple, the characteristic length is the inner droplet radius or the fiber radius. [less ▲]

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See detailFollow the guide
Filoux, Boris ULiege; Hubert, Maxime ULiege; Vandewalle, Nicolas ULiege

Poster (2015, May 13)

When gently placing a droplet onto a vertically vibrated bath, under specific conditions, coalescence may be avoided. The drop bounces permanently. Upon increasing the forcing acceleration, the drop ... [more ▼]

When gently placing a droplet onto a vertically vibrated bath, under specific conditions, coalescence may be avoided. The drop bounces permanently. Upon increasing the forcing acceleration, the drop interacts with the wave it generates, and becomes a walker [1,2]. Recently, some 2D confining systems for walking droplets have been developed: cylindrical cavity, harmonic potential or the use of Coriolis force [3,4]. In addition, the interactions between two identical walkers have been studied in a 2D case [5]. Nevertheless, no study focuses on 1D dynamics and their properties. In this work, we show it is possible to confine a walker in a quasi mono-dimensional geometry by using a submerged annular cavity. We focus on the interactions between droplets, and show the interdistance quantization. Then, we study the speed of pairs of walkers and show that the distance between the drops affects the group speed: the closer the drops are, the faster they move. We also propose a numerical model to characterize the distance quantization, and the evolution of the speed of a string of droplets. Finally, we investigate the case of a string of droplets. We discuss the influence of the number of droplets and the distance between droplets on the string speed. 1. Y. Couder, S. Protière, E. Fort, and A. Boudaoud, Nature 437, 208 (2005).
 2. S. Protière, A. Boudaoud, and Y. Couder, J. Fluid Mech. 554, 85 (2006).
 3. S. Perrard, M. Labousse, M. Miskin, E. Fort, and Y. Couder, Nat. Commun. 5, 3219 (2014).
 4. M. Labousse and S. Perrard, Phys. Rev. E 90, 022913 (2014).
 5. C. Borghesi, J. Moukhtar, M. Labousse, A. Eddi, E. Fort, and Y. Couder, Phys. Rev. E 90, 063017 (2014). [less ▲]

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See detailBiosensor based on optical fibers
Lismont, Marjorie ULiege; Vandewalle, Nicolas ULiege; Joris, Bernard ULiege et al

Poster (2015, May)

Medical diagnosis and biotechnology progresses are strongly dependent on the development of sensing devices, which, ideally, would allow the reliable detection of very low amounts of biological species in ... [more ▼]

Medical diagnosis and biotechnology progresses are strongly dependent on the development of sensing devices, which, ideally, would allow the reliable detection of very low amounts of biological species in various environments. In addition to these requirements, the detection tools would also be easy to use and would rapidly response. Fluorescent based biosensors fulfil most of these characteristics. In our work, the intersection between two crossed optical fibers is used as the basic unit of an original optical biosensor. As illustrated by figure 1, one optical fiber is used to carry probe molecules and excite fluorescence while the second one is devoted to carry the target species and collect the optical signal arising from the species interacting at the node. The advantages of our set-up over traditional optical sensors are no surface functionalization, use of low amounts of biological species, limitation of the denaturation risk, ease to use and low detection threshold. The developed biosensor is validated on two systems. The first one is a fluorescent calcium indicator, Oregon green 488 BAPTA-2, whose optical emission signal is affected by Ca2+ ions concentration. The second one is based on Rh-Con A and FITC-Dextran complex for which the FRET phenomenon is affected by glucose concentration. In both cases, the results are in agreement with the ones obtained in cuvettes attesting the efficiency of the sensing device. We also show a prototype of a multichannel device composed of multiple crossed optical fibers which are used as species and light carriers. [less ▲]

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