References of "Gilet, Tristan"
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See detailDroplet formation by squeezing in a microfluidic cross-junction
Van Loo, Stéphanie ULg; Stoukatch, Serguei ULg; Kraft, Michael ULg et al

in Microfluidics and Nanofluidics (2016), 20(10), 1-12

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here report an experimental study of droplet formation in a microfluidic cross ... [more ▼]

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here report an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the squeezing regime, which is composed of two distinct steps : filling and pinching. The duration of each step (and corresponding volumes of each liquid phase) are analyzed. They vary according to both water and oil flow rates. These variations provide several insights about the fluid flows in both phases. We propose several scaling laws to relate the droplet volume and frequency to the flow rate of both phases. We also discuss the influence of surfactant and channel compliance on droplet formation. [less ▲]

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See detailHow do droplets form?
Van Loo, Stéphanie ULg; Stoukatch, Serguei ULg; Kraft, Michael ULg et al

Poster (2016, September 07)

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here report an experimental study of droplet formation in a microfluidic cross ... [more ▼]

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here report an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the squeezing regime, which is com- posed of two distinct steps : filling and pinching. The duration of each step (and corresponding volumes of each liquid phase) are analyzed. They vary according to both water and oil flow rates. These variations provide several insights about the fluid flows in both phases. We propose several scaling laws to relate the droplet volume and frequency to the flow rate of both phases. We also discuss the influence of surfactant and channel compliance on droplet formation. [less ▲]

Detailed reference viewed: 67 (14 ULg)
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See detailElastocapillarity in Dock Beetle Adhesion
Gernay, Sophie-Marie ULg; Federle, Walter; Lambert, Pierre et al

Poster (2016, September)

Miniaturization is currently limited by our ability to manipulate micrometer-sized objects. Insect adhesion is an advantageous bio-inspired solution to this problem, although it is not fully understood ... [more ▼]

Miniaturization is currently limited by our ability to manipulate micrometer-sized objects. Insect adhesion is an advantageous bio-inspired solution to this problem, although it is not fully understood yet. Interference Reflection Microscopy images of the beetle Gastrophysa Viridula adhesive structures in contact with a smooth substrate were analyzed. The results were cross-linked with an analytical model of an elastic beam deflected by a liquid meniscus. By fitting the unknown model parameters to the experimental data, we obtained information about the elastic properties of the structures, the liquid volume in the bridge, and the resulting adhesion levels. [less ▲]

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See detailElasto-capillarity in insect fibrillar adhesion
Gernay, Sophie-Marie ULg; Federle, Walter; Lambert, Pierre et al

in Journal of the Royal Society, Interface (2016), 13(121),

The manipulation of microscopic objects is challenging because of high adhesion forces, which render macroscopic gripping strategies unsuitable. Adhesive footpads of climbing insects could reveal ... [more ▼]

The manipulation of microscopic objects is challenging because of high adhesion forces, which render macroscopic gripping strategies unsuitable. Adhesive footpads of climbing insects could reveal principles relevant for micro-grippers, as they are able to attach and detach rapidly during locomotion. However, the underlying mechanisms are still not fully understood. In this work, we characterize the geometry and contact formation of the adhesive setae of dock beetles (Gastrophysa viridula) by interference reflection microscopy. We compare our experimental results to the model of an elastic beam loaded with capillary forces. Fitting the model to experimental data yielded not only estimates for seta adhesion and compliance in agreement with previous direct measurements, but also previously unknown parameters such as the volume of the fluid meniscus and the bending stiffness of the tip. In addition to confirming the primary role of surface tension for insect adhesion, our investigation reveals marked differences in geometry and compliance between the three main kinds of seta tips in leaf beetles. [less ▲]

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See detailThe mysteries of droplet birth in microfluidic cross junctions
Van Loo, Stéphanie ULg; Gilet, Tristan ULg

Poster (2016, March 24)

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here present an experimental study of droplet formation in a microfluidic cross ... [more ▼]

In microfluidics, flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. We here present an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the dripping regime. The dynamics of droplet formation is composed of two distinct steps : filling and pinching. The duration of each step (and cor- responding volumes of each phase) are analyzed. They vary according to both water and oil flow rates. These variations reveal several insights about the fluid flows in both phases. We propose some scaling laws to relate the droplet volume and frequency to the flow rate of both phases. We also discuss the influence of surfactant on droplet formation. [less ▲]

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See detailTwo-frequency forcing of droplet rebounds on a liquid bath
Sampara, Naresh; Gilet, Tristan ULg

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

Droplets can bounce indefinitely on a liquid bath vertically vibrated in a sinusoidal fashion. We here present experimental results that extend this observation to forcing signals composed of a ... [more ▼]

Droplets can bounce indefinitely on a liquid bath vertically vibrated in a sinusoidal fashion. We here present experimental results that extend this observation to forcing signals composed of a combination of two commensurable frequencies. The Faraday and Goodridge thresholds are characterized. Then a number of vertical bouncing modes are reported, including walkers. The vertical motion can become chaotic, in which case the horizontal motion is an alternation of walk and stop. [less ▲]

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See detailLa soif de nectar
Gilet, Tristan ULg; Kim, Wonjung; Bush, John W.M.

Article for general public (2016)

Le nectar des fleurs est une nourriture de choix pour de nombreux animaux : papillons, fourmis, abeilles, colibris, et même chauve- souris à l’occasion. Pour attirer ces pollinisateurs potentiels, les ... [more ▼]

Le nectar des fleurs est une nourriture de choix pour de nombreux animaux : papillons, fourmis, abeilles, colibris, et même chauve- souris à l’occasion. Pour attirer ces pollinisateurs potentiels, les plantes concoctent une variété de nectars plus ou moins riches en sucre. Sous quelles contraintes l’animal fait-il alors son choix ? Y a-t-il des nectars dont il est plus opportun de se nourrir ? Pourquoi les papillons et les colibris se dirigent-t-ils spontanément vers un nectar moins concentré que celui préféré par les abeilles ? [less ▲]

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See detailQuantumlike statistics of deterministic wave-particle interactions in a circular cavity
Gilet, Tristan ULg

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

A deterministic low-dimensional iterated map is proposed here to describe the interaction between a bouncing droplet and Faraday waves confined to a circular cavity. Its solutions are investigated ... [more ▼]

A deterministic low-dimensional iterated map is proposed here to describe the interaction between a bouncing droplet and Faraday waves confined to a circular cavity. Its solutions are investigated theoretically and numerically. The horizontal trajectory of the droplet can be chaotic: it then corresponds to a random walk of average step size equal to half the Faraday wavelength. An analogy is made between the diffusion coefficient of this random walk and the action per unit mass h/m of a quantum particle. The statistics of droplet position and speed are shaped by the cavity eigenmodes, in remarkable agreement with the solution of Schrödinger equation for a quantum particle in a similar potential well. [less ▲]

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See detailThe mysterious droplet birth in a microfluidic cross junction
Van Loo, Stéphanie ULg; Gilet, Tristan ULg

Conference (2015, November 23)

In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could ... [more ▼]

In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could not be identified yet, owing to the large number of parameters involved (incl. complex geometry). We here present an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the dripping regime. The formation sequence is decomposed in two steps, inflation and squeezing, that vary differently according to both water and oil flow rates. These variations reveal several insights about the fluid flows in both phases. From there we infer the scaling law that relates droplet volume and frequency to the Capillary number associated to each inlet flow rate. This law involves a minimum of fitting parameters. We finally discuss the influence of inlet control (flow rate vs. pressure) and surfactants on the formation dynamics. [less ▲]

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See detailElastocapillarity in insect adhesion: IRM investigation
Gernay, Sophie-Marie ULg; Federle, Walter; Lambert, Pierre et al

Conference (2015, June)

The feet of many insects are covered with dense arrays of micrometric hair-like structures called setae. Liquid capillary bridges formed at the tip of these slender structures are responsible for the ... [more ▼]

The feet of many insects are covered with dense arrays of micrometric hair-like structures called setae. Liquid capillary bridges formed at the tip of these slender structures are responsible for the controlled adhesion of the insect on a large variety substrates. The resulting adhesion force is very efficient: it can exceed several times the body weight of the insect and yet vanish in a few milliseconds for fast detachment. The high aspect-ratio of setae suggests that flexibility is a key ingredient in this capillary-based adhesion mechanism. There is indeed a strong coupling between their elastic deformation and the shape of the liquid meniscus. In this experimental work, we observe and quantify the local deflection of dock beetle (Gastrophysa viridula) seta tips under perpendicular loading using interference reflection microscopy (IRM). Our results are then interpreted in the light of an analytic model of elastocapillarity through which we gain information about the optimal regime that these insects target. [less ▲]

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See detailUnraveling expressionism
truscott, tadd; Darbois-Texier, Baptiste ULg; lovett, benjamin et al

Conference (2015)

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See detailFluid fragmentation shapes rain-induced foliar disease transmission
Gilet, Tristan ULg; Bourouiba, Lydia

in Journal of the Royal Society, Interface (2015), 12

Plant diseases represent a growing threat to the global food supply. The factors contributing to pathogen transmission from plant to plant remain poorly understood. Statistical correlations between ... [more ▼]

Plant diseases represent a growing threat to the global food supply. The factors contributing to pathogen transmission from plant to plant remain poorly understood. Statistical correlations between rainfalls and plant disease out- breaks were reported; however, the detailed mechanisms linking the two were relegated to a black box. In this combined experimental and theoretical study, we focus on the impact dynamics of raindrops on infected leaves, one drop at a time. We find that the deposition range of most of the pathogen-bear- ing droplets is constrained by a hydrodynamical condition and we quantify the effect of leaf size and compliance on such constraint. Moreover, we identify and characterize two dominant fluid fragmentation scenarios as responsible for the dispersal of most pathogen-bearing droplets emitted from infected leaves: (i) the crescent-moon ejection is driven by the direct interaction between the impacting raindrop and the contaminated sessile drop and (ii) the inertial detachment is driven by the motion imparted to the leaf by the raindrop, lead- ing to catapult-like droplet ejections. We find that at first, decreasing leaf size or increasing compliance reduces the range of pathogen-bearing droplets and the subsequent epidemic onset efficiency. However, this conclusion only applies for the crescent moon ejection. Above a certain compliance threshold a more effective mechanism of contaminated fluid ejection, the inertial detachment, emerges. This compliance threshold is determined by the ratio between the leaf velocity and the characteristic velocity of fluid fragmentation. The inertial detachment mechanism enhances the range of deposition of the larger con- taminated droplets and suggests a change in epidemic onset pattern and a more efficient potential of infection of neighbouring plants. Dimensionless parameters and scaling laws are provided to rationalize our observations. Our results link for the first time the mechanical properties of foliage with the onset dynamics of foliar epidemics through the lens of fluid fragmentation. We discuss how the reported findings can inform the design of mitigation strategies acting at the early stage of a foliar disease outbreak. [less ▲]

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See detailElastocapilllarity in insect adhesion: the case of beetle adhesive hairs
Gernay, Sophie-Marie ULg; Federle, Walter; Lambert, Pierre et al

Conference (2014, November)

The feet of many insects are covered with dense arrays of hair-like structures called setae. Liquid capillary bridges at the tip of these micrometric structures are responsible for the controlled adhesion ... [more ▼]

The feet of many insects are covered with dense arrays of hair-like structures called setae. Liquid capillary bridges at the tip of these micrometric structures are responsible for the controlled adhesion of the insect on a large variety of substrates. The resulting adhesion force can exceed several times the body weight of the insect. The high aspect-ratio of setae suggests that flexibility is a key ingredient in this capillary-based adhesion mechanism. There is indeed a strong coupling between their elastic deformation and the shape of the liquid meniscus. In this experimental work, we observe and quantify the local deflection of dock beetle seta tips under perpendicular loading using interference microscopy. Our results are then interpreted in the light of an analytic model of elastocapillarity. [less ▲]

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See detailDroplet synchronization in multiple interconnected parallel channels
Van Loo, Stéphanie ULg; Stoukatch, Serguei ULg; Gilet, Tristan ULg

Poster (2014, July)

In droplet microfluidics, the pairing of droplets in parallel channels is sometimes required, e.g. to control their encounter and to promote their coalescence. Prakash and Gershenfeld [1] showed that ... [more ▼]

In droplet microfluidics, the pairing of droplets in parallel channels is sometimes required, e.g. to control their encounter and to promote their coalescence. Prakash and Gershenfeld [1] showed that passive synchronization could be achieved with bubbles in a ladder-like channel network. Bubbles flow in the rails and induce recirculation in the interconnecting rungs, which supposedly provides the feedback and subsequent synchronization. Ahn et al. recently extended this study to trains of droplets in flow-rate-driven conditions [2]. We here present an extensive experimental and theoretical investigation of droplets synchonization in multiple parallel channels. Droplets are produced with independent flow-focusing structures. Several experimental conditions are tested, including several geometries (and subsequent flow resistance) and inlet conditions (pressure-driven vs. flow-rate-driven). An extension to three rails is also considered. The microfluidic chips are designed with the help of a lumped-element model in which droplets are driven by the flows. [1] M. Prakash and N. Gershenfeld, Science 2007, 315, 832-835 [2] Ahn et al., Lab-on-a-chip, 2011, 11, 3956-3962 [less ▲]

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See detailRain-operated Foliar Disease Transmission
Gilet, Tristan ULg; Bourouiba, Lydia

Conference (2014, January 07)

Plant diseases are a major cause of crop loss worldwide. They are known to be triggered by rainfalls. We here combine high-speed visualizations and physical modelling to elucidate the causal link between ... [more ▼]

Plant diseases are a major cause of crop loss worldwide. They are known to be triggered by rainfalls. We here combine high-speed visualizations and physical modelling to elucidate the causal link between rain impact on foliage and pathogen spreading. We identify two dominant scenarios by which the pathogens get ejected from leaves. The leaf compliance is shown to strongly affect these mechanisms. The laws of fluid dynamics set tight limits on this epidemiological problem. They suggest a revision of the current agricultural practices in order to contain the spread of foliar diseases. [less ▲]

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See detailElastic behaviour of dock beetle adhesive structures
Gernay, Sophie-Marie ULg; Federle, Walter; Lambert, Pierre et al

Conference (2014, January)

The adhesion of many insects is mediated by liquid capillary bridges formed at the tips of multiple hair like structures (called setae) under their feet. Resulting adhesion forces can exceed a hundred ... [more ▼]

The adhesion of many insects is mediated by liquid capillary bridges formed at the tips of multiple hair like structures (called setae) under their feet. Resulting adhesion forces can exceed a hundred times the insect’s body weight and they are effective on a large variety of substrates, controllable in very short times and self cleaning. The underlying mechanism leading to these properties involves a complex coupling between the high aspect-ratio structures and the dynamic evolution of the liquid meniscus. In this experimental work, we concentrate on the role played by the compliance of seta tips. We analyse in detail their surface contact and deflection for perpendicular loading using interference microscopy. Challenges related to the micrometric scale of the phenomenon and the tiny amount of liquid are addressed. The results are rationalized through the lens of elasto-capillarity theory. [less ▲]

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See detailDynamics and statistics of wave-particle interactions in a confined geometry
Gilet, Tristan ULg

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2014), 90

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See detailRain-induced Ejection of Pathogens from Leaves: Revisiting the Hypothesis of Splash-on-Film using High-speed Visualization
Gilet, Tristan ULg; Bourouiba, Lydia

in Integrative & Comparative Biology (2014), 54

Detailed reference viewed: 25 (2 ULg)
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See detailDroplets bouncing on a wet, inclined substrate
Gilet, Tristan ULg; Bush, John W.M.

in Physics of Fluids (2012), 24

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See detailManipulation of Droplets onto a Planar Interface
Gilet, Tristan ULg; Terwagne, Denis ULg; Vandewalle, Nicolas ULg et al

in miller, reinhard; liggieri, libero (Eds.) Progress in Colloid and Interface Science, 2 (2011)

Detailed reference viewed: 78 (16 ULg)