Abstract: Yielding is a phenomenon in which a material transitions from elastic deformation to viscous dissipation when subjected to large deformations. This transition has been described and studied for over a century, but it remains elusive to predict, characterize, and design in soft materials. This challenge arises in part from ambiguity over definitions, limitations in instrumentation and protocol, and a lack of theoretical models that describe the nonlinear relationship between material structure, dynamics, and properties. Our group has been working to address these challenges, which we will discuss in three parts. First, we develop a novel rheological protocol – serial creep divergence – to unambiguously define yielding even in the presence of shear induced structural transitions. Second, we introduce high-performance rheological additives based on telechelic block copolymers that can controllably modify the elasticity of emulsions. And finally, we demonstrate that the nonlinear response of soft materials can be almost entirely predicted by a combination of the linear viscoelasticity and steady-state flow stress. This relationship holds across material chemistry and structure and orders of magnitude in material elasticity and therefore shows that the same fundamental physics controlling the viscoelastic response under linear deformations is preserved across the yield transition. These findings not only elucidate the mechanisms underlying the yield transition in soft materials, but they also motivate the development of high-performance materials with tunable yielding characteristics for use in applications ranging from personal care to advanced manufacturing.
Bio: Dr. Ryan Poling-Skutvik is an Assistant Professor in the Department of Chemical, Biomolecular, and Materials Engineering at the University of Rhode Island with a limited joint appointment in the Department of Physics. He received his B.E. in Chemical Engineering from the Cooper Union for the Advancement of Science and Art in 2013 and his Ph.D. in Chemical Engineering from the University of Houston in 2018. He joined the Department of Chemical Engineering at the University of Rhode Island in 2020 after completing his postdoctoral research at the University of Pennsylvania. His research expertise combines rheology, microscopy, and scattering to identify hierarchical behavior in complex soft materials. His research has been recognized the ACS Petroleum Research Fund Doctoral New Investigator award, the NSF CAREER award, and the Cottrell Scholar award. Additionally, he serves as the Scholarship Director as part of the URI ESTEEMED program focusing on training the next generation of bioengineers and conducts outreach efforts targeted at increasing the participation of LGBTQ+ youth in STEM fields.