Nanobubbles at solid-liquid interfaces: why are they there?
By: Rogério Colaço
From: Departamento de Engenharia de Materiais and Instituto de Ciência e Engenharia de
Materiais e Superfícies, Instituto Superior Técnico, Lisboa, Portugal
At: Complexo Interdisciplinar, Anfiteatro
[2009-05-06]
Nanobubbles trapped at a solid-liquid interfaces are intriguing nano-objects claimed to have an ubiquitous presence in a considerable number of situations: the long range attractions between hydrophobic surfaces immersed in water, the superhydrophobic effect in lotus-leaf like surfaces or in special types of fabrics, the stability of colloidal systems, the formation of gas bubbles in biological marine systems submitted to rapid decompression, among others. Nevertheless, understanding the causes of their existence and, moreover, of their long-time stability if far from being accomplished: from a physical point of view, indeed, nanobubbles should not exist. In this lecture I will present a review of experimental evidences for the existence of nanobubbles and on the attempts of establishing theoretical bases to understand nanobubbles. Then I will talk about the reasons why a materials engineer (myself) is interested on nanobubbles: they could explain discrepancies on the measurement of adhesion forces in biotribological materials. Moreover, we could, in fact, observe them at some solid-liquid interfaces by using Phase Shift Mode Atomic Force Microscopy (PSM-AFM). Finally I will present you a rough attempt of building a thermodynamical model for the stability of trapped nanobubbles.