Université Paris Est, Laboratoire Navier, UMR 8205 CNRS - École des Ponts ParisTech - IFSTTAR, cité Descartes, 2 allée Kepler, 77420 Champs-sur-Marne, France.
Université Paris Est, Laboratoire Navier, UMR 8205 CNRS - École des Ponts ParisTech - IFSTTAR, 5 bd Descartes, 77454 Marne-la-Vallée Cedex 2, France.
J Colloid Interface Sci. 2017 Sep 1;501:103-111. doi: 10.1016/j.jcis.2017.04.033. Epub 2017 Apr 12.
Elasticity of soft materials can be greatly influenced by the presence of air bubbles. Such a capillary effect is expected for a wide range of materials, from polymer gels to concentrated emulsions and colloidal suspensions. Whereas experimental results and theory exist for describing the elasto-capillary behavior of bubbly materials (i.e. with moderate gas volume fractions), foamy systems still require a dedicated study in order to increase our understanding of elasticity in aerated materials over the full range of gas volume fractions. Here we elaborate well-controlled foams with concentrated emulsion and we measure their shear elastic modulus as a function of gas fraction, bubble size and elastic modulus of the emulsion. Such complex foams possess the elastic features of both the bubble assembly and the interstitial matrix. Moreover, their elastic modulus is shown to be governed by two parameters, namely the gas volume fraction and the elasto-capillary number, defined as the ratio of the emulsion modulus with the bubble capillary pressure. We connect our results for foams with existing data for bubbly systems and we provide a general view for the effect of gas bubbles in soft elastic media. Finally, we suggest that our results could be useful for estimating the shear modulus of aqueous foams and emulsions with multimodal size distributions.
软物质的弹性会受到气泡存在的极大影响。这种毛细效应预计在广泛的材料范围内存在，从聚合物凝胶到浓缩乳液和胶体悬浮液。尽管已经存在实验结果和理论来描述多泡材料（即中等气体体积分数）的弹毛细管行为，但泡沫系统仍需要专门研究，以便在整个气体体积分数范围内增加我们对充气材料弹性的理解。在这里，我们详细介绍了具有浓缩乳液的可控泡沫，并测量了它们的剪切弹性模量作为气体分数、气泡大小和乳液弹性模量的函数。这种复杂的泡沫具有气泡组装和间隙基质的弹性特征。此外，它们的弹性模量由两个参数控制，即气体体积分数和弹毛细管数，定义为乳液模量与气泡毛细压力的比值。我们将泡沫的结果与多泡系统的现有数据联系起来，并提供了一个关于气体气泡在软弹性介质中影响的综合观点。最后，我们建议我们的结果可用于估计具有多模态尺寸分布的水基泡沫和乳液的剪切模量。
