Paper Number
TM10 My Program
Session
Techniques and Methods: Rheometry, Tribometry, Spectroscopy and Microscopy
Title
Boger yield stress fluids in gravity-driven filament stretching
Presentation Date and Time
October 22, 2025 (Wednesday) 10:50
Track / Room
Track 7 / Sweeney Ballroom D
Authors
- Livesay, Thomas A. (University of Illinois, Urbana-Champaign, Department of Mechanical Science and Engineering)
- 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
Thomas A. Livesay, Mohammad Tanver Hossain and Randy H. Ewoldt
Department of Mechanical Science and Engineering, University of Illinois, Urbana-Champaign, Urbana, IL 61801
Speaker / Presenter
Livesay, Thomas A.
Keywords
experimental methods; computational methods; industrial applications; methods; non-Newtonian fluids; polymer solutions; rheometry; techniques
Text of Abstract
Yield stress fluids can be highly extensible [1]. However, current methods to characterize this extensibility with filament stretching can suffer from boundary adhesion issues, unstable or asymmetric filament formation, artifacts from delayed necking, and difficulties in accessing high strain rates. Here, we study how extensional gravity-rheometry (EGR), developed for simple yield-stress fluids [2], can be extended to more complex yield stress fluids with high elasticity including “Boger yield stress fluids” with tunable extensibility [3]. Thin filaments are often generated; we derive and test how to incorporate surface tension effects into the working equations and identify operational limits where key assumptions are violated. We consider a range of fluids, including Newtonian fluids, archetypal yield stress fluids, and model extensible yield stress fluids formulated with polyethylene oxide (PEO) and Carbopol microgel particles [3]. Using quantitative video image analysis, we track filament deformation during extrusion to calculate the instantaneous strain rate and tensile stresses at the minimum filament radius, enabling inference of instantaneous, local extensional rheological properties. We demonstrate this technique can be used to reveal high extensibility and extensional thickening in these model extensional yield stress fluids, beyond what has typically been observed in filament stretching tests, made possible by probing higher strain rate regimes [4]. These results broaden the applicability of the extensional gravity-rheometry test to a wider classification of fluids, enabling advancements in high throughput, in situ material characterization, as well as in construction, additive manufacturing, and 3D printing applications.
[1] Nelson, A. Z. et al., J. Rheol, (2018). DOI: 10.1122/1.5003841
[2] Geffrault, A. et al., J. Rheol. (2021). DOI: 10.1122/8.0000241
[3] Sen S. et al., Soft Matter, (2023). DOI: 10.1039/d3sm01150j
[4] Szabo, P. et al., JNNFM, (2012). DOI: 10.1016/j.jnnfm.2011.11.003