Hierarchical anti-adhesive materials by mimicking insect traps

我们的目的是阐明肉食性猪笼草分层组织的抗粘捕器官的结构/性质关系，并设计仿生原型。完成了模式植物Nepenthes alata罐中所有三个层次（第1级：月状细胞；第2级：下层蜡层；第3级：上层蜡层）的结构特征，确定了复杂蜡覆盖发展的连续阶段，并显示了下层蜡层缺乏再生能力。我们通过探测昆虫的附着，在全球尺度上考察了完整层次系统的粘附特性，并证明了生物水平1的特定各向异性特性。我们在局部尺度上对2级和3级进行了物理化学和机械表征，并开发了一种实验方法来测量粘附力非常低的表面上的粘附力。用力学稳定的聚合物球阵列模拟1级月骨细胞。即使没有生物水平1月骨细胞的各向异性，后者的粘附力也比平面对照组低一个数量级。在生物模型和仿生系统中，2级不会减少粘附。对于生物模型，仅在下层和上层蜡层（2级和3级）的组合中发现附着力降低。我们将在人工抗粘合剂中实现纳米棒涂层作为生物启发的3级，可能允许可靠的一次性脱离粘附表面，例如，在冰存在的情况下。我们将在全球和局部尺度上评估不同蜡层在阿拉木图瓶中的吸收能力以及蜡晶尺寸对附着力的影响。研究了其他食肉属植物不同功能猪笼表面的微观结构和润湿特性。为了研究流体在仿生抗胶粘剂接触界面上的作用，将通过膨胀诱导嵌段共聚物的形态重建来制备含有连续孔系统的单个仿生层次及其组合。生物启发样品将通过光学显微镜、扫描电子显微镜、原子力显微镜、白光干涉测量和接触角测量来表征。拔离力测试将在干燥条件下和接触界面有水的情况下进行。我们将系统地阐明(1)仿生级3的影响，(2)仿生级3与其他层次的相互作用，(3)接触区的流体，(4)表面的极性/亲水性对仿生样品在干湿条件下的抗粘接性能的影响。多孔仿生抗胶粘剂将系统地与它们的固体对应物进行比较。

We aim at elucidation of structure/property relations in hierarchically organised anti-adhesive trapping organs of carnivorous pitcher plants and at the design of bio-inspired prototypes. Structural characterisation of all three hierarchical levels (level 1: lunate cells; level 2: lower wax layer; level 3: upper wax layer) in pitchers of the model plant Nepenthes alata was completed, successive stages in the development of the complex wax coverage were determined, and the absence of the regeneration ability in the lower wax layer was shown. We examined adhesive properties of the complete hierarchical system on the global scale by probing insect attachment and demonstrated specific anisotropic properties of biological level 1. We performed physicochemical and mechanical characterisation of levels 2 and 3 on the local scale and developed an experimental approach for measuring adhesion forces on surfaces with very low adhesive capability. Level 1 lunate cells were mimicked by mechanically stable arrays of polymer spheres. The adhesion of the latter was one order of magnitude lower than that of flat controls, even without the anisotropy of biological level 1 lunate cells. Level 2 in both the biological model and bio-inspired systems does not reduce adhesion. For the biological model reduced adhesion is only found for combinations of lower and upper wax layers (levels 2 and 3). We will implement nanorod coatings as bio-inspired level 3 in artificial anti-adhesives that may allow for reliable one-time detachment of adhering surfaces, for example, in the presence of ice.We will evaluate the absorption ability of different wax layers in N. alata pitchers and the influence of the wax crystal size on adhesion at global and local scales. Microstructure and wetting properties of different functional pitcher surfaces in plants from other carnivorous genera will be characterized. To study the role of fluids at the contact interface of bio-inspired anti-adhesives, single bio-inspired hierarchical levels and combinations thereof containing continuous pore systems will be made by swelling-induced morphology reconstruction of block copolymers. The bio-inspired samples will be characterized by light microscopy, scanning electron microscopy, atomic force microscopy, white light interferometry, and contact angle measurements. Pull-off force tests will be carried out under dry conditions and in the presence of water at the contact interface. We will systematically elucidate the effect of (1) the bio-inspired level 3, (2) the interplay of the bio-inspired level 3 with other hierarchical levels, (3) the fluid at the contact zone, and (4) the polarity/hydrophilicity of the surface on anti-adhesive properties of bio-inspired samples under dry and wet conditions. Porous bio-inspired anti-adhesives will be systematically compared with their solid counterparts.