<br/>The coming end of earth's fossil energy is pressing humanity to develop more efficient and environmentally friendly technologies. Control of wear and fatigue of machine parts has become one of the most important field of research to meet the outstanding energy crisis the world is currently facing. The design of lubricating fluids able to protect fragile surfaces against wear and high friction has been one the several tools used by engineers to improve machines’ life time. Inspired by many different biological systems that can resist fatigue wear for decades such as our synovial joints, different coating/lubricating technologies involving polymer brushes either in their molecular form or grafted on the surface have emerged.<br/>We will describe our efforts in the design of lubricating systems designed to protect efficiently fragile materials such as hydrogels. Such systems use synergistic mixtures of bottle brushes (BB) and linear polymer solutions that mimic human synovial fluid and microstructured surfaces that control the lubricating fluid flow during shear. We will show that mixtures of a bottle brush and a linear polymer in pure water or in saline allows to drastically increase wear protection of structured and unstructured hydrogels under a wide range of shearing conditions. We demonstrate that this synergy between the BB and linear polymer emerges from a strong, yet transient, cohesion between the two components forming the boundary film due to entanglements between both polymers. Hydrogels with a two-layers structure mimicking articular cartilage exhibit stronger wear resistance compared to unstructured hydrogels. We show that the presence of a dense hydrogel layer on top of the shearing surfaces provides enhanced fluid pressurization and excellent wear protection but poor lubrication (high friction coefficient). On the other hand, hydrogels with microchannels pointing towards the surface exhibit excellent lubrication (low friction coefficient) but very poor wear protection. Combination of structure and bioinspired lubricating fluid allows to mitigate these effect of hydrogel structure and to finally obtain superlubricating and superresistant hydrogel surfaces. Different applications of these materials will be described in the biomedical field.

Lubrication and wear protection of soft materials using bioinspired polymers

2019 Fall National Meeting

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