Paper Number
RS5 

Session
Techniques and Methods: Rheometry & Spectroscopy/Microscopy

Title
Stress-controlled optimally windowed chirp rheometry (σ-OWCh) for the characterisation of materials undergoing a sol-gel transition

Presentation Date and Time
October 11, 2022 (Tuesday) 11:10

Track / Room
Track 6 / Mayfair

Authors (Click on name to view author profile)

  1. Hudson, Rebecca E. (Swansea University, Complex Fluids Research Group)
  2. Holder, Alex J. (Swansea University, Complex Fluids Research Group)
  3. Rathinaraj, Joshua D. (Massachusetts Institute of Technology, Department of Mechanical Engineering)
  4. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)
  5. Curtis, Daniel J. (Swansea University, Complex Fluids Research Group)

Author and Affiliation Lines (in printed abstract book)
Rebecca E. Hudson1, Alex J. Holder1, Joshua D. Rathinaraj2, Gareth H. McKinley2 and Daniel J. Curtis1
1Complex Fluids Research Group, Swansea University, Swansea, Wales SA1 8EN, United Kingdom; 2Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02142

Speaker / Presenter 
Hudson, Rebecca E.

Keywords
experimental methods; gels

Text of Abstract
Frequency modulated (chirp) waveforms have previously been used for the rapid characterisation of viscoelastic materials using strain-controlled protocols (e.g. Geri et al., 2018). However, stress-controlled rheometric protocols are often more appropriate for strain sensitive or gelling materials. Here, we establish a stress-based chirp protocol (σ-OWCh) for the study of such materials. Experiments conducted on a single head rheometer under stress-controlled conditions suffer from an inherent strain offset which can be removed using a baseline correction for conventional rheometric techniques. Removing the strain offset using a baseline correction is not straightforward in chirp based rheometry. Therefore, we propose seeking the complex viscosity, η*(ω), as an intermediate parameter for the complex modulus, G*(ω), to overcome this problem. The σ-OWCh protocol is then demonstrated in the study of biopolymer gelation.