CPOS Seminar: Design and Tribological Characterization of Stimuli-Responsive Hydrogels
Speaker: Allison Chau, 5th yr graduate student, Materials Department, UCSB, Pitenis Group
Abstract: Aqueous, low friction interfaces are ubiquitous in biology – from articular cartilage that coats synovial joints to mucin layers that act as a lubricating barrier for epithelial surfaces throughout the body. Hydrogels, three-dimensional networks of crosslinked hydrophilic polymer chains swollen in water, are often utilized as synthetic mimics for these biological systems due to their high water content, lubricity, and tunable mechanical properties. There is a great need to investigate the tribological properties (e.g., friction) of hydrogels to elucidate the lubrication mechanisms driving their behavior in order to design hydrogels with tunable friction coefficients.
In this work, we will discuss the tribological behavior of two stimuli-responsive hydrogel systems: poly(acrylamide-co-acrylic acid) (P(AAm-co-AA)) and poly(N-isopropylacrylamide-co-spiropyran methacrylate) (pNIPAAm-co-SP). In these systems, the friction coefficient was tuned at least one order of magnitude with pH and light, respectively. The swelling behavior and elastic modulus changes of the hydrogels are also investigated along with potential lubrication mechanisms. The results from these studies can be applied to situations that require tunable tribological properties, such as in soft robotics or haptics.
