H. Kellay
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View article: Non-Markovian dynamics of a torsion pendulum immersed in an active bath
Non-Markovian dynamics of a torsion pendulum immersed in an active bath Open
A torsion pendulum can probe a variety of phenomena such as photon spin or gravity, uncover the properties of spider draglines or examine stochastic thermodynamics of driven systems. Here we use such a device to probe the state of an assem…
View article: Active particle in a very thin interfacial droplet
Active particle in a very thin interfacial droplet Open
A single light-driven Janus particle confined in a very thin oil droplet at an air-water interface displays intriguing dynamics. While laser activation induces rapid horizontal motion ( 1 m m / s – 1 c m / s ) by thermal Marangoni fl…
View article: Roadmap for animate matter
Roadmap for animate matter Open
Humanity has long sought inspiration from nature to innovate materials and devices. As science advances, nature-inspired materials are becoming part of our lives. Animate materials, characterized by their activity, adaptability, and autono…
View article: Partial wetting of water on ice
Partial wetting of water on ice Open
Is ice always covered by a thin layer of water? This question has been discussed for over 150 years. Here we show that the apparent contact angle of a droplet of water on ice increases steeply with decreasing ice temperature, from around 1…
View article: Evidence and quantification of memory effects in competitive first-passage events
Evidence and quantification of memory effects in competitive first-passage events Open
Splitting probabilities quantify the likelihood of a given outcome out of competitive events. This key observable of random walk theory, historically introduced as the gambler’s ruin problem, is well understood for memoryless (Markovian) p…
View article: Active particle in a very thin interfacial droplet
Active particle in a very thin interfacial droplet Open
A single light-driven Janus particle confined in a very thin oil droplet at an air--water interface displays intriguing dynamics. While laser activation induces rapid horizontal motion (1mm/s--1cm/s) by thermal Marangoni flow, the particle…
View article: Controlled Locomotion of a Minimal Soft Structure by Stick-Slip Nonlinearity
Controlled Locomotion of a Minimal Soft Structure by Stick-Slip Nonlinearity Open
We present a locomotion mechanism that uses the stick-slip transition of a soft passive structure with an internal mechanical resonance. The structure is harmonically driven by a global vertical shaking and, because of its resonance dephas…
View article: Enhanced Pyroelectricity Over Extended Thermal Range in Flexible Polymer Thin Films
Enhanced Pyroelectricity Over Extended Thermal Range in Flexible Polymer Thin Films Open
Polymer‐based pyroelectric thin films are crucial functional materials at the core of flexible and lightweight electronic devices, such as wearable monitoring sensors, energy harvesters, and infrared detectors. Nevertheless, the pyroelectr…
View article: Roadmap for Animate Matter
Roadmap for Animate Matter Open
Humanity has long sought inspiration from nature to innovate materials and devices. As science advances, nature-inspired materials are becoming part of our lives. Animate materials, characterized by their activity, adaptability, and autono…
View article: Granular Scaling Approach to Landslide Runout
Granular Scaling Approach to Landslide Runout Open
A main objective in landslide research is to predict how far they will travel. Landslides are complex, and a complete understanding in principle requires accounting for numerous parameters. Here we engender a simplification by investigatin…
View article: Air drag controls the runout of small laboratory landslides
Air drag controls the runout of small laboratory landslides Open
Laboratory granular landslides are smaller-scale, simplified, yet well-controlled versions of larger and often tragic natural landslides. Using systematic experiments and scaling analysis, we quantify the influence of grain size, fall heig…
View article: Evidence and quantification of memory effects in competitive first passage events
Evidence and quantification of memory effects in competitive first passage events Open
Splitting probabilities quantify the likelihood of a given outcome out of competitive events. This key observable of random walk theory, historically introduced as the gambler's ruin problem, is well understood for memoryless (Markovian) p…
View article: Viscoelastic rheology of polymer solution probed by resonant thermal capillary fluctuation
Viscoelastic rheology of polymer solution probed by resonant thermal capillary fluctuation Open
We present a measurement of viscoelastic properties of polymer solutions using resonant thermal capillary fluctuations of the surface of a polymer solution droplet. The instantaneous deflection of a cantilever in contact with the drop surf…
View article: Effective temperature and dissipation of a gas of active particles probed by the vibrations of a flexible membrane
Effective temperature and dissipation of a gas of active particles probed by the vibrations of a flexible membrane Open
International audience
View article: Activity Induced Rigidity of Liquid Droplets
Activity Induced Rigidity of Liquid Droplets Open
Here we show that encapsulating active Janus particles within a drop renders it more resistant to deformation. This drop is deformed under the action of an extensional flow. Such deformation is primarily resisted by the drop interfacial te…
View article: The effect of tilt on turbulent thermal convection for a heated soap bubble
The effect of tilt on turbulent thermal convection for a heated soap bubble Open
We use direct numerical simulation (DNS) to explore the effect of tilt on two-dimensional turbulent thermal convection on a half-soap bubble that is heated at its equator. In the DNS, the bubble is tilted by an angle δ∈[0°,90°], the Raylei…
View article: Droplet impacts on cold surfaces
Droplet impacts on cold surfaces Open
We study drop impact for the case where the impacted surface is cooled below the freezing temperature of the liquid droplet. The freezing is found to affect the spreading dynamics of the impacting drops and, thus, the degree of surface cov…
View article: A Hydrodynamic Analog of the Casimir Effect in Wave-Driven Turbulent Flows
A Hydrodynamic Analog of the Casimir Effect in Wave-Driven Turbulent Flows Open
We present experimental results on a fluctuation-induced force observed in Faraday wave-driven turbulence. As recently reported, a long-range attraction force arises between two walls that confine the wave-driven turbulent flow. In the Far…
View article: Universal Aspects of Droplet Spreading Dynamics in Newtonian and Non-Newtonian Fluids
Universal Aspects of Droplet Spreading Dynamics in Newtonian and Non-Newtonian Fluids Open
Droplet impacts are common in many applications such as coating, spraying, or printing; understanding how droplets spread after impact is thus of utmost importance. Such impacts may occur with different velocities on a variety of substrate…
View article: Universal aspects of droplet spreading dynamics in Newtonian and non-Newtonian Fluids
Universal aspects of droplet spreading dynamics in Newtonian and non-Newtonian Fluids Open
Droplet impacts are common in many applications such as coating, spraying, or printing; understanding how droplets spread after impact is thus of utmost importance. Such impacts may occur with different velocities on a variety of substrate…
View article: Experimental and numerical study of laser-induced secondary jetting
Experimental and numerical study of laser-induced secondary jetting Open
The generation of liquid jets and drops using tightly focused femtosecond laser pulses near a liquid–air interface is a convenient contactless solution for printing functional materials as well as bio-materials. Jets and drops emerge follo…
View article: From collections of independent, mindless robots to flexible, mobile, and directional superstructures
From collections of independent, mindless robots to flexible, mobile, and directional superstructures Open
Self-organization of independent simple robots confined in a flexible scaffold gives rise to a mobile and flexible structure.
View article: Delamination and Wrinkling of Flexible Conductive Polymer Thin Films
Delamination and Wrinkling of Flexible Conductive Polymer Thin Films Open
Polymer based conductive and transparent thin films are an important class of functional materials at the heart of flexible organic electronic devices. These flexible films are prone to degradation and to mechanical instability leading to …
View article: Asymptotic turbulent friction in 2D rough-walled flows
Asymptotic turbulent friction in 2D rough-walled flows Open
In turbulent rough-walled flows, the 2D friction-roughness relation differs from its 3D counterpart.
View article: A landslide granular phase transition
A landslide granular phase transition Open
Landslides appear in many different forms and sizes, from devastating debris flows to overly optimistic sand castles. A familiar and well-documented feature of all landslides is the positive correlation between volume and landslide runout.…
View article: Impact of the Wetting Length on Flexible Blade Spreading
Impact of the Wetting Length on Flexible Blade Spreading Open
We study the spreading of a Newtonian fluid by a deformable blade, a common industrial problem, characteristic of elastohydrodynamic situations. Here, we consider the case of a finite reservoir of liquid, emptying as the liquid is spread. …
View article: Sorting and Extraction of Self-Propelled Chiral Particles by Polarized Wall Currents
Sorting and Extraction of Self-Propelled Chiral Particles by Polarized Wall Currents Open
The dynamics of self-propelled particles with curved trajectories is investigated. Two modes are observed, a bulk mode with a quasicircular motion and a surface mode with the particles following the walls. The surface mode is the only mode…
View article: Numerical Study of Rotating Thermal Convection on a Hemisphere
Numerical Study of Rotating Thermal Convection on a Hemisphere Open
Numerical simulations of rotating two-dimensional turbulent thermal convection on a hemisphere are presented in this paper. Previous experiments on a half soap bubble located on a heated plate have been used for studying thermal convection…