Ménisque (physique)

Résumé

Le ménisque est la partie courbe de la surface d'un liquide qui apparaît au voisinage de la surface du contenant ou d'un autre objet, souvent solide, lorsque l'orientation de la surface de l'objet n'est pas compatible avec celle de la surface du liquide. Il peut donc disparaître ou s'inverser lorsqu'on change l'orientation de l'objet. L'orientation compatible est dictée par l'angle de contact entre le fluide et la surface de l'objet. Cet angle dépend de la nature chimique du liquide et de celle du solide, ainsi que de la rugosité éventuelle du solide. Il dépend du ratio entre la tension de surface liquide-gaz (c'est-à-dire le coût énergétique d'une interface air-fluide) et la tension de surface liquide-contenant (ou force d'adhésion). Il est déterminé à l'aide de la loi de Young-Dupré : \cos\theta=\frac{\gamma_{SV}-\gamma_{SL}}{\gamma_{LV}} où : \gamma_{SV}, \gamma_{SL} et \gamma_{LV} désignent respectivement la tension superficiel

Source officielle

https://fr.wikipedia.org/wiki/M%C3%A9nisque_(physique)

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This study presents an analytical model of the dynamics of an axisymmetric liquid bridge confined between two circular pads and subjected to small vertical periodic perturbations. Such system finds important applications in microassembly and microjoint design, where force and damping need to be precisely controlled. The liquid bridge is modelled by an equivalent spring/dashpot/mass system characterised by the spring constant k, the damping coefficient b and the equivalent mass m, respectively. An abacus for k as well as analytical approximations for k, b and m based on simplifications of the Navier–Stokes equation are provided. The study is validated by experiments and numerical simulations of the system. We describe the experimental setup we designed to investigate vertical forces arising on the bottom pad from small periodic perturbations of the top pad confining the liquid meniscus. The setup allowed the accurate control of all physical and geometrical parameters relevant for the experiments. The parameters we investigated are both physical (viscosity and surface tension of the fluid) and geometrical (the edge angle between the meniscus and the pad, the height of the meniscus). The good agreement between model predictions and results let us conclude that k, b and m involve only one physical property of the liquid, namely the surface tension, the viscosity and the density, respectively.

Elsevier2013

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Modeling capillary forces for large displacements

Pierre Lambert, Massimo Mastrangeli

Originally applied to the accurate, passive positioning of submillimetric devices, recent works proved capillary self-alignment as effective also for larger components and relatively large initial offsets. In this paper, we describe an analytic quasi-static model of 1D capillary restoring forces that generalizes existing geometrical models and extends the validity to large displacements from equilibrium. The piece-wise nature of the model accounts for contact line unpinning singularities ensuing from large perturbations of the liquid meniscus and dewetting of the bounding surfaces. The superior accuracy of the generalized model across the extended displacement range, and particularly beyond the elastic regime as compared to purely elastic models, is supported by finite element simulations and recent experimental evidence. Limits of the model are discussed in relation to the aspect ratio of the meniscus, contact angle hysteresis, tilting and self-alignment dynamics.

Springer Verlag2015

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In-Plane Mode Dynamics of Capillary Self-Alignment

Pierre Lambert, Massimo Mastrangeli

We present an experimental study of the complete in-plane dynamics of capillary self-alignment. The two translational (shift) and single rotational (twist) in-plane modes of square millimetric transparent dies bridged to shape-matching receptor sites through a liquid meniscus were selectively excited by preset initial offsets. The entire self-alignment dynamics was simultaneously monitored over the three in-plane degrees of freedom by high-speed optical tracking of the alignment trajectories. The dynamics of the twist mode is shown to qualitatively follow the sequence of dynamic regimes also observed for the shift modes, consisting of initial transient wetting, acceleration toward, and underdamped harmonic oscillations around the equilibrium position. Systematic analysis of alignment trajectories for individually as well as simultaneously excited modes shows that, in the absence of twist offset, the dynamics of the degenerate shift modes are mutually independent. In the presence of twist offset, the three modes conversely evidence coupled dynamics, which is attributed to a synchronization mechanism affected by the wetting of the bounding surfaces. The experimental results, justified by energetic, wetting, and dynamic arguments, provide substantial benchmarks for understanding the full dynamics of the process.

American Chemical Society2014

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