Défense de thèse de doctorat en sciences physiques : "surface multifunctionality"

Electrodynamical approach of surface multifunctionality : the tuning of the Lifshitz-van der Waals interactions

Jury

Serge REYNAUD (Université Pierre et Marie Curie, Paris), Joël DE CONINCK (Université de Mons), Philippe LAMBIN, président (UNamur), Michaël SARRAZIN, co-promoteur (UNamur), Olivier DEPARIS, promoteur (UNamur)

Résumé

For a long time, anti-reflective properties have a major importance in the development of optical devices. For instance, anti-reflective coatings are required when designing telescopes, camera lenses, solar cells or glass windows. In another context, superhydrophobicity, i.e the ability of a surface to exhibit a static water contact angle equal or greater than 150◦, is a key property for numerous industrial applications. Indeed, superhydrophobic surfaces can exhibit self-cleaning properties. As a matter of fact, a surface or coating that could combine both anti-reflective and superhydrophobic properties is highly interesting. However, this achievement of such multifunctional surfaces is far from being easily reachable, not only from experimental aspects but also from fundamental physics.

In literature, from a theoretical point of view, superhydrophobicity and antireflection are almost always studied separately. In this thesis work, we propose an elegant and unified theory for jointly dealing with these two problems. The way to tackle this issue relies on Lifshitz-van der Waals interaction theory. These appear as a major contribution to the interaction potential energy in many interfacial phenomena within macroscopic systems. Taking origin from quantum vacuum fluctuations, the Lifshitz-van der Waals interactions are shown to be tunable via properly designed antireflective nanostructured surfaces. The impact of this tuning in terms of surface multifunctionality is discussed and the concept is applied to two general practical cases:  the superhydrophobic surface and the switching from attractive to repulsive Lifshitz-van der Waals forces.

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