Wetting of Auxetic Metamaterials

这是一个普遍的概念，当材料被拉伸时，它会变薄。然而，当一个缺乏的材料被拉伸时，它变得更宽（它具有负泊松比）。因为材料不是无界的，所以它们有表面。表面不可避免地会接触到液体。然而，令人惊讶的是，目前还没有发表的研究考虑到增减材料的不寻常性质如何改变固液相互作用，影响液体在固体表面上的扩散方式或液滴的撞击和反弹行为。更令人惊讶的是，膨胀聚四氟乙烯（ePTFE）， GoreTex中的微孔超疏水防水和透气层，可以很容易地转化为一种auxetic形式。当补充材料扩大其表面积时，是通过在晶格的固体框架内增加空间来实现的。因此，我们可以预期表面润湿特性的变化。这种类型的变化将导致表面的固体表面（Cassie）分数随着固体组分之间的空间增加而减少。固体和液体表面积之间的平衡对于如何通过表面形貌/纹理将表面化学特性放大为超液体驱避、半吸汗和其他润湿特性至关重要。它还可以控制表面是液体可以粘住的还是液体看起来很滑的。缓蚀材料具有不寻常的抗冲击性能，因为材料流向而不是远离冲击区域。这为液滴撞击和反弹的材料和表面提供了新的方法。因此，在这个项目中，我们专注于使材料科学能够创造一类新的润湿材料，我们称之为“辅助润湿超材料”。该项目考虑了一系列制造增氧材料的技术，重点关注固体表面积分数和空间面积分数之间的平衡如何随应变变化。该项目考虑了这种固体表面积分数如何随应变变化，结合亲疏水性来控制表面的整体润湿特性和这些新材料的润湿状态转变。它将在实验上这样做，并得到理论方案以及建模和模拟的支持。这项工作还将考虑如何利用应变来控制液体摩擦和液滴反弹。

It is a common conception that when a material is stretched it becomes thinner. However, when an auxetic material is stretched it becomes wider (it possesses a negative Poisson's ratio). Since materials are never unbounded, they have surfaces. And surfaces inevitably come into contact with liquids. However, surprisingly, there is no published research that considers how the unusual properties of auxetic materials change the solid-liquid interaction and influence how liquids spread on the solid surface or the impact and rebound behaviour of droplets. It is even more surprising because expanded polytetrafluoroethylene (ePTFE), the microporous superhydrophobic waterproof and breathable layer in GoreTex, can be easily converted to an auxetic form. When auxetic materials expand their surface area, it is by an increase in the space within the solid frame of a lattice. We can therefore expect changes to the wetting properties of the surface. This type of change will cause the solid surface (Cassie) fraction of the surface to decrease as the space between solid components increases. This balance between solid and liquid surface area is critical to how the surface chemistry properties are amplified by the surface topography/texture into super-liquid repellence, hemi-wicking and other wetting properties. It also controls whether the surface is one to which a liquid will stick or one which appears slippery to a liquid. An auxetic material has unusual impact resistance properties because material flows towards, rather than away, from the area of an impact. This offers a new approach to materials and surfaces for droplet impact and rebound.In this project we therefore focus on the enabling materials-science to create a new class of wetting materials, which we refer to as "Auxetic Wetting Metamaterials". The project considers a range of techniques to fabricate auxetic materials with a focus on how the balance between solid surface area fraction and space area fraction change with strain. The project considers how this solid surface area fraction change with strain combines with hydrophilic and hydrophobic properties to manipulate the overall wetting properties of the surfaces and the wetting state transitions of these new materials. It will do so experimentally and be supported by a theoretical programme and by modelling and simulation. The work will also consider how strain can be used to control liquid friction and droplet rebound.