Unraveling the mechanisms of soft-matter lubrication is pivotal in understanding the functionalities and complexities of biological soft-matter and biolubrication. Biphasic materials, such as hydrogels, are key components in multiple natural tribosystems such as the articular and ocular lubrication systems. Yet, the origin of damage of such tribosystems still remains convoluted. While static friction and stick-slip have been proposed as precursors to damage and wear of soft interfaces, there is a lack of fundamental knowledge and framework. We investigate static friction and contact ageing of polyacrylamide hydrogels with three different microstructures using Atomic Force Microscopy (AFM). A conceptual phase diagram for hydrogels’ static friction is developed where a subtle solid-like to liquid-like change of behavior is observed[endif]--&gt;within the investigated range of temperatures. Furthermore, two characteristic peaks are mechanistically explained to result from two competitive mechanisms associated with the biphasic nature of hydrogels. We propose that depending on the hydrogel’s microstructure, normal load, loading time and temperature, different behaviors can be probed on the static friction phase diagram. The knowledge emerging from this work will help inspire customized design of materials in a wide variety of fields having a core interest in tribology.

Static friction phase diagram for hydrogel-like materials

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.