laboratoire de physique statistique
 
 
laboratoire de physique statistique

Publications

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Bruno ANDREOTTI 


2
P U B L I C A T I O N S

S E L E C T I O N N E R
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2016
Defects at the Nanoscale Impact Contact Line Motion at all Scales - Perrin, Hugo and Lhermerout, Romain and Davitt, Kristina and Rolley, Etienne and Andreotti, Bruno
PHYSICAL REVIEW LETTERS 116 (2016) 
LPS


Abstract : The contact angle of a liquid drop moving on a real solid surface depends on the speed and direction of motion of the three-phase contact line. Many experiments have demonstrated that pinning on surface defects, thermal activation and viscous dissipation impact contact line dynamics, but so far, efforts have failed to disentangle the role of each of these dissipation channels. Here, we propose a unifying multiscale approach that provides a single quantitative framework. We use this approach to successfully account for the dynamics measured in a classic dip-coating experiment performed over an unprecedentedly wide range of velocity. We show that the full contact line dynamics up to the liquid film entrainment threshold can be parametrized by the size, amplitude and density of nanometer-scale defects. This leads us to reinterpret the contact angle hysteresis as a dynamical crossover rather than a depinning transition.
A moving contact line as a rheometer for nanometric interfacial layers - Lhermerout, Romain and Perrin, Hugo and Rolley, Etienne and Andreotti, Bruno and Davitt, Kristina
NATURE COMMUNICATIONS 7 (2016) 
LPS


Abstract : How a liquid drop sits or moves depends on the physical and mechanical properties of the underlying substrate. This can be seen in the hysteresis of the contact angle made by a drop on a solid, which is known to originate from surface heterogeneities, and in the slowing of droplet motion on deformable solids. Here, we show how a moving contact line can be used to characterize a molecularly thin polymer layer on a solid. We find that the hysteresis depends on the polymerization index and can be optimized to be vanishingly small (< 0.07 degrees). The mechanical properties are quantitatively deduced from the microscopic contact angle, which is proportional to the speed of the contact line and the Rouse relaxation time divided by the layer thickness, in agreement with theory. Our work opens the prospect of measuring the properties of functionalized interfaces in microfluidic and biomedical applications that are otherwise inaccessible.