Department of Mechanical Engineering, Boston University, Boston, MA 02215, USA.
Soft Matter. 2017 Dec 6;13(47):8903-8909. doi: 10.1039/c7sm01676j.
When coated with microscale hydrophobic particles, macroscopic liquid droplets can become non-wetting liquid marbles that exhibit an array of fascinating solid-like properties. Specifically, the force required to uniaxially compress liquid marbles depends on their volume, but it is unclear if the particle coating plays a role. In contrast, the failure of marbles upon compression does depend on the particle coating, but the conditions for failure do not appear to change with marble volume. Here, we experimentally study the elastic deformation and failure of liquid marbles and, by applying a doubly truncated oblate spheroid model to quantify their surface area, explore the role of marble volume and particle composition. First, we find that the work required to compress liquid marbles agrees with the product of the core fluid surface tension and the change in the marble surface area, validating that the elastic mechanics of liquid marbles is independent of the particle coating. Next, we study marble failure by measuring their ductility as quantified by the maximum fractional increase in marble surface area prior to rupture. Not only does marble ductility depend on the particle coating, but it also depends on marble volume with smaller marbles being more ductile. This size effect is attributed to an interaction between marble curvature and particle rafts held together by interparticle forces. These results illuminate new avenues to tailor the rupture of liquid marbles for applications spanning smart fluid handling and pollution mitigation.
当涂覆有微观疏水颗粒时，宏观液滴可以变成具有一系列迷人固体特性的非润湿液滴。具体来说，单轴压缩液滴所需的力取决于其体积，但颗粒涂层是否起作用尚不清楚。相比之下，液滴在压缩下的失效确实取决于颗粒涂层，但失效条件似乎不会随液滴体积的变化而改变。在这里，我们通过实验研究了液滴的弹性变形和失效，并通过应用双截断扁球模型来量化其表面积，探讨了液滴体积和颗粒组成的作用。首先，我们发现压缩液滴所需的功与核心流体表面张力和液滴表面积变化的乘积一致，验证了液滴的弹性力学独立于颗粒涂层。接下来，我们通过测量液滴在破裂前表面面积最大增加分数来研究液滴的延展性，即延展性，发现液滴的延展性不仅取决于颗粒涂层，还取决于液滴体积，体积较小的液滴更具延展性。这种尺寸效应归因于液滴曲率和由颗粒间力保持在一起的颗粒筏之间的相互作用。这些结果为针对跨越智能流体处理和污染缓解的应用定制液滴破裂开辟了新途径。
