Hierarchical anti-adhesive materials by mimicking insect traps

我们的目标是阐明肉食性猪笼草防粘连诱捕器官的层次结构/性质关系，并设计生物灵感原型。完成了模式植物猪笼草3个层级(1层：月形细胞；2层：下层蜡层；3层：上层蜡层)的结构特征，确定了复杂蜡层形成的连续阶段，表明下层蜡层缺乏再生能力。我们通过探测昆虫附着在全球尺度上检验了完整层级系统的黏附特性，并展示了生物1级的特殊各向异性特性。我们在局部尺度上对2级和3级进行了物理化学和力学表征，并发展了一种测量黏附力的实验方法，该方法适用于黏附能力很低的表面。1级月形细胞由机械稳定的聚合物球阵列模拟。即使没有生物水平1月形细胞的各向异性，后者的粘附性也比扁平对照组低一个数量级。生物模型和生物启发系统中的第二级都不会减少粘附性。对于生物模型，只有较低和较高蜡层(2级和3级)的组合才能发现粘附性降低。我们将在人工防粘剂中实现纳米棒涂层作为生物灵感级别3，这可能允许附着表面的可靠一次性分离，例如，在有冰的情况下。我们将评估不同蜡层在水壶中的吸附能力，以及在全球和局部尺度上蜡晶尺寸对附着力的影响。将描述其他肉食性属植物不同功能水壶表面的微观结构和润湿特性。为了研究流体在仿生防粘剂接触界面上的作用，通过溶胀诱导嵌段共聚物的形态重构，得到了含有连续孔系统的单个仿生层级及其组合。受生物启发的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进行表征。拉拔力测试将在干燥条件下和接触界面有水的情况下进行。我们将系统地阐述(1)生物启发第三级，(2)生物启发第三级与其他层级的相互作用，(3)接触区的流体，以及(4)表面的极性/亲水性对生物启发样品在干燥和潮湿条件下的防粘连性能的影响。多孔生物仿生防粘剂将与固体防粘剂进行系统的比较。

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.