Discovering the Mechanisms of Hydrogel Surface Weakening and Wear Under Applied Sliding Conditions

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

Hydrogels are flexible plastic materials that have water integrated into the structure. This hydration helps make them slippery and biocompatible, so they are used as thin biomedical devices such as contact lenses and catheter coatings, as well as in the oil industry as soft particles. New chemistries of hydrogel are developed every day for targeted applications such as drug delivery, prosthetic soft devices, and synthetic soft tissues. However, retaining durability of soft, slippery materials in these intended applications when they are sliding against other materials is important for their success. The specific ways that hydrogels degrade under sliding is not yet known, so this award supports the fundamental discovery of connections between the hydrogel structure, sliding conditions, and surface durability. These connections will result in new mechanical design guidelines for manufacturing hydrogels, impacting health and industrial sectors. Because this research connects materials properties to mechanical performance, it is well-suited as the basis for interdisciplinary activities targeted to empower underrepresented minority students in science and engineering. The friction and lubrication properties at the interface of soft hydrated materials determine the collective behavior of dense microgel systems, but friction is often treated as a simple function of slip velocity or shear rate. Materials-based lubrication theories for soft hydrated matter have recently emerged, along with experimental evidence of hydrogel surface wear. The research goal of this project is to discover the mechanisms of surface degradation in soft interfaces due to surface shear by applying, measuring in situ, and mapping the progression of mechanical degradation in slipping, low-friction hydrogel interfaces. Instrumented micro-tribometry, optical- and force-based microscopy, and micro-indentation will be employed to measure the progression of degradation. This knowledge will contextualize competing theories of hydrogel lubrication and catalyze hypotheses regarding chemical and physical degradation of hydrogels for emerging scientific, technological, and engineering design problems