Advanced bio-inspired adhesive materials

先进的制造技术已经证明了微制造聚合物材料的可行性，这些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，利用范德华分子间相互作用。这是通过创造一种表面的微观结构来实现的，这种微观结构由微和纳米尺度的柱子组成，称为原纤维。随着这些原纤维尖端产生的密切接触，范德华力就产生了。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局粘附力。一般来说，这种现象不涉及永久的化学键合，因此，只要用于粘合的材料界面的机械和几何特征不恶化，它就可以无限期地重复。从工业机器人到极端环境（如微重力）的运动，从这种仿生合成粘合剂衍生的新兴技术的扩散，给固体力学的框架带来了新的挑战，需要改进这种材料的设计。只有对所涉及的现象有更深入的了解，才能指导这种改进。例如，纤维状粘接剂材料在每个长度尺度上的脱离机制仍未完全了解。文献报道了对单个纤维脱离的大量研究，而大量纤维的相互作用仍然通常被忽视。这产生了粗略的近似，特别是考虑到界面缺陷的尺寸通常可以在比单个原纤维更大的长度尺度上发现。我的目的是研究这种界面在多个长度尺度上的分离机制，并由此推断出适用于多个结构层次的改进设计原则。此外，应该注意到，迄今为止，关于这一主题的理论和实验工作都集中在不可变形表面的粘附上，而忽略了粘附材料的顺应性。新兴可穿戴技术的激增，在某些情况下可以看到设备植入人体，这引起了对开发“生物相容性”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粘在生物组织上。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.