Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

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.