Advanced bio-inspired adhesive materials

先进的制造技术已经证明了利用范德华分子间相互作用微制造聚合物材料的可行性，这种材料可以模仿壁虎脚趾垫的可逆和可重复使用的粘合性能。这是通过创造一种被称为纤维的微米和纳米柱子组成的表面微结构来实现的。随着这些纤维尖端产生亲密接触，范德华力就会产生。这种形式的分层接触细分允许在宏观尺度上产生相关的全球粘附力。一般来说，这种现象不涉及永久性的化学键，因此，只要用于粘合的材料界面的机械和几何特征不恶化，这种现象就可以无限重复。从工业机器人到极端环境(如微重力)中的移动，源于这种生物启发的合成粘合剂的新兴技术的激增，给固体力学框架带来了新的挑战，需要改进此类材料的设计。只有更深入地了解所涉及的现象，才能指导这种改进。例如，纤维粘结材料的剥离机理在每一种长度尺度上仍未完全了解。文献报道了大量关于单一原纤维分离的研究，而多个原纤维之间的相互作用仍被普遍忽视。这产生了粗略的近似，特别是考虑到界面缺陷的大小通常可以在比单个纤维更大的长度尺度上找到。我的目的是研究这种界面在多个长度尺度上分离的机制，并由此推导出适用于多个层次结构层次的改进设计原则。此外，应该注意到，到目前为止，关于这一主题的理论和实验工作主要集中在不可变形表面上的粘接，从而忽略了粘接材料的柔顺性。新兴的可穿戴技术的激增，在某些情况下可以看到设备被植入人体，这引发了开发“生物兼容”粘合材料的需求。这种材料应该能够以可逆和可重复使用的方式附着在生物组织上。这一新的挑战激发了拟议研究计划的主要目标。

Advanced manufacturing technologies have proven the feasibility of micro-fabrication of polymeric materials that can mimic the reversible and reusable adhesive properties of gecko toe pads, utilizing van der Waals intermolecular interaction. This is achieved by creation of a superficial microstructure comprised of micro- and nano-metric pillars called fibrils. With intimate contact generated at the tip of these fibrils, van der Waals forces develop. Hierarchical contact subdivision of this form allows for the generation of a relevant global adhesive force at the macroscopic scale. In general no permanent chemical bonding is involved in this phenomenon, and as such it can be repeated indefinitely as long as the mechanical and geometrical features of the interface of the material intended for adhesion do not deteriorate. The proliferation of the emerging technologies derived from such bio-inspired synthetic adhesives, which range from industrial robotics to locomotion in extreme environments (e.g. microgravity), is bringing new challenges to the framework of solid mechanics in the need for improved design of such materials. Such improvements can only be guided by a deeper knowledge of the phenomena involved. For example, the mechanism of detachment of fibrillar adhesive materials is still not completely understood at every length scale. The literature reports a large number of investigations of the detachment of one single fibril, while the mutual interaction of a multitude of them is still commonly neglected. This yields crude approximations, particularly given that the size of interfacial defects can be commonly found at a larger length scales than that of individual fibrils. My aim is to investigate the mechanism of detachment of such interfaces at multiple length scales and, from this, deduce improved design principles to be applied across multiple levels of structural hierarchy. Furthermore, it should be observed that thus far theoretical and experimental work done on this subject has been focused on the adhesion on non-deformable surfaces thus neglecting the compliance of the adhered material. The proliferation of emerging wearable technologies, which in some cases see the implantation of devices on the human body, is giving rise to a need for the development of “bio-compatible” adhesive materials. Such materials should be capable of sticking on biological tissue in a reversible and reusable manner. This new challenge has inspired the main goal of the proposed research program.