Paper Number
GN36 My Program
Session
Self-assemblies, Gels and Networks
Title
Protorheology à la critical gel
Presentation Date and Time
October 22, 2025 (Wednesday) 10:30
Track / Room
Track 2 / Sweeney Ballroom B
Authors
- Marsh, Maxwell C. (University of Illinois Urbana-Champaign)
- Hossain, Mohammad Tanver (University Of Illinois Urbana-champaign, Mechanical Science and Engineering)
- Ewoldt, Randy H. (University Of Illinois Urbana-champaign, Mechanical Science and Engineering)
Author and Affiliation Lines
Maxwell C. Marsh, Mohammad Tanver Hossain and Randy H. Ewoldt
University of Illinois Urbana-Champaign, Urbana, IL 61801-3180
Speaker / Presenter
Marsh, Maxwell C.
Keywords
experimental methods; gels; methods; rheometry
Text of Abstract
The significance of the critical gel point has been known for decades. However, no prior study has combined a comprehensive rheometric dataset paired with non-trivial flow observations that demonstrate the consequences of critical gel rheology, such as spreadability, high damping, and extensional thickening. Here, we select a realistic model material with thermal gelation and mutation, widely accessible and colloquially understood (egg yolk), and present a detailed library of temperature-dependent linear and nonlinear oscillatory, creep, and stress relaxation data [1]. Furthermore, in the spirit of protorheology [2] we provide high quality visuals of the flow consequences of being a realistic critical gel. These materials mutate during testing, complicating gel point determination. Moreover, any claim of “solid” behavior depends on the timescale of observation (diverging zero-shear viscosity and emerging equilibrium modulus in the case of a critical gel). Our work highlights the mutation timescale in this material as well as the observation timescale present in any rheological test. One common test to approximate a gel point is to measure the dynamic moduli in oscillation and observe when they cross over. While the rheological community has known for decades that this is not a true critical gel point, many outside our community continue to use the moduli crossover as a metric. We propose an alternative way to interpret the same data: using diverging dynamic viscosity eta' with careful consideration of the timescale of observation (oscillatory time scale). By integrating protorheology observations with rigorous rheometric data and new interpretation techniques, this work enables a deeper understanding of critical gel behavior.
[1] Marsh M. et al., “Egg yolk as a model for gelation: from rheometry to flow physics,” Phys. Fluids 37, 043114 (2025). https://doi.org/10.1063/5.0255929
[2] Hossain, M. et al., “Protorheology,” J. Rheol. 68(1), 113–144 (2024). https://doi.org/10.1122/8.0000667