Hyperuniform anodic aluminium oxide (hAAO): a 2D metamaterial with improved mechanicalproperties for hard-soft bilayer composite actuators

超均匀阳极氧化铝 (hAAO)：一种具有改进的机械性能的二维超材料，适用于硬软双层复合材料执行器

• 批准号: 519853330
• 负责人: Professor Dr. Patrick Huber
• 金额: --
• 依托单位: Institut für Chemie neuer Materialien
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/519853330?language=en
• 关键词: Hyperuniform; anodic; aluminium; oxide; hAAO

Hyperuniform disordered (HuD) structures are statistically isotropic without translational symmetry but exhibit a hidden symmetry by suppressing long-range density fluctuations. 2D HuD structures contain no grain boundaries or specific crystallographic directions along which crack propagation can occur. Thus, improved 2D mechanical metamaterials with superior fracture strength may be accessible by hyperuniformity design. Porous anodic aluminum oxide (AAO) membranes are produced by anodization of aluminum. They contain arrays of straight and parallel cylindrical pores oriented normal to the membrane plane with diameters ranging from a few 10 nm to a few 100 nm. Under appropriate conditions, self-ordering of the growing pores into hexagonal domains occurs. So far, research on AAO has predominantly aimed at the improvement of the pore ordering. Here, we consider the AAO pores as discrete elements enabling 2D in-plane hyperuniformity design. Thus, we plan to produce AAO with 2D hyperuniform pore arrangements (hAAO) resulting in improved resistance to fracture propagation and, therefore, improved fracture strength. For this purpose, rational design of disorder in AAO pore arrays will be achieved by departures from the narrow parameter windows (self-ordering regimes) in which mild anodization of aluminum results in self-ordered pore growth. In our preliminary work we already obtained nearly hyperuniform AAO, suggesting that AAO is a promising candidate for an effectively hyperuniform 2D mechanical metamaterial that nearly perfectly matches the ideal model theoretically devised by Torquato. Using hAAO as model system, we aim at the experimental validation of 2D hyperuniformity as a generic concept to optimize the mechanical properties of freestanding thin hard layers. By marrying the concepts “mechanical metamaterial” and “shape-changing material”, we will establish hAAO as platform for the design of hard-soft bilayer composites that can reversibly or permanently change their shape in response to triggers even under extreme conditions, such as high operating temperatures. As shown in preliminary experiments, AAO-polystyrene (PS) bilayer composites show pronounced reversible shape changes in response to temperature changes caused by the different thermal expansion behavior of PS and AAO. Adhesion and mechanical coupling between hAAO and polymer layer will be enhanced because the polymer partially infiltrates the hAAO pores. Also, hAAO enhances the hardness of the bilayer composites under operating conditions and reduces energy dissipation by unwanted local deformations during shape changes. In an exploratory activity, all-porous bilayer composites consisting of hAAO and a block copolymer (BCP) layer bent by volume expansion of the BCP caused by solvent swelling will be evaluated as curved crossflow ultrafiltration membranes with enhanced mechanical stability and improved anti-fouling behaviour.

超均匀无序 (HuD) 结构在统计上是各向同性的，没有平移对称性，但通过抑制长程密度波动而表现出隐藏的对称性。 2D HuD 结构不包含裂纹扩展可能发生的晶界或特定晶体方向。因此，通过超均匀性设计可以得到具有优异断裂强度的改进二维机械超材料。多孔阳极氧化铝 (AAO) 膜是通过铝的阳极氧化生产的。它们包含垂直于膜平面定向的直平行圆柱形孔阵列，直径范围从几十纳米到几百纳米。在适当的条件下，生长的孔会自排序成六边形区域。迄今为止，AAO 的研究主要针对孔有序性的改善。在这里，我们将 AAO 孔视为离散元素，从而实现二维面内超均匀性设计。因此，我们计划生产具有二维超均匀孔隙排列 (hAAO) 的 AAO，从而提高抗断裂扩展能力，从而提高断裂强度。为此，AAO 孔阵列无序的合理设计将通过偏离窄参数窗口（自排序机制）来实现，其中铝的温和阳极氧化会导致自排序孔生长。在我们的前期工作中，我们已经获得了近乎超均匀的 AAO，这表明 AAO 是有效超均匀二维机械超材料的有希望的候选者，它几乎完美地匹配 Torquato 理论上设计的理想模型。使用 hAAO 作为模型系统，我们的目标是对二维超均匀性作为通用概念进行实验验证，以优化独立式薄硬层的机械性能。通过结合“机械超材料”和“形状改变材料”的概念，我们将建立 hAAO 作为硬软双层复合材料的设计平台，即使在高工作温度等极端条件下，该复合材料也可以根据触发条件可逆或永久地改变其形状。如初步实验所示，AAO-聚苯乙烯 (PS) 双层复合材料由于 PS 和 AAO 的不同热膨胀行为而导致温度变化，表现出明显的可逆形状变化。由于聚合物部分渗透到 hAAO 孔中，hAAO 和聚合物层之间的粘附力和机械耦合将得到增强。此外，hAAO 还提高了双层复合材料在操作条件下的硬度，并减少了形状变化过程中不必要的局部变形造成的能量耗散。在一项探索性活动中，由 hAAO 和嵌段共聚物 (BCP) 层组成的全孔双层复合材料，由于溶剂膨胀导致 BCP 体积膨胀而弯曲，将被评估为弯曲横流超滤膜，具有增强的机械稳定性和改善的防污性能。