Paper Number
PO73                         My Program 

Session
Poster Session

Title
Large Amplitude Oscillatory Extension (LAOE) of complex fluids in planar elongation

Presentation Date and Time
October 16, 2024 (Wednesday) 6:30

Track / Room
Poster Session / Waterloo 3 & 4

Authors (Click on name to view author profile)

  1. Recktenwald, Steffen M. (Okinawa Institute of Science and Technology Graduate Univers, Micro,Bio,Nanofluidics Unit)
  2. Shen, Amy Q. (Okinawa Institute of Science and Technology Graduate Univers, Micro,Bio,Nanofluidics Unit)
  3. Haward, Simon J. (Okinawa Institute of Science and Technology Graduate Univers, Micro,Bio,Nanofluidics Unit)

Author and Affiliation Lines (in printed abstract book)
Steffen M. Recktenwald, Amy Q. Shen and Simon J. Haward
Micro,Bio,Nanofluidics Unit, Okinawa Institute of Science and Technology Graduate Univers, Onna-son, Okinawa 904-0495, Japan

Speaker / Presenter 
Recktenwald, Steffen M.

Keywords
experimental methods; flow-induced instabilities; non-Newtonian fluids; polymer solutions; polymers

Text of Abstract
Oscillatory shear tests are commonly used to understand the flow behavior of soft matter and complex fluids like polymer melts, biological fluids, and food products. These materials often experience significant deformations in real-world applications, and it is crucial to measure their nonlinear properties to predict how they will respond in different conditions. Large Amplitude Oscillatory Shear (LAOS) tests play a critical role in helping us understand how soft materials behave when subjected to nonlinear shear deformations. Despite advances in characterizing nonlinear material properties in shear flows, the potential of oscillatory flows for elucidating the extensional properties of complex fluids is mainly unexplored. However, extension-dominated and mixed flows are crucial for a wide range of industrial applications, including fiber spinning, ink-jet printing, and blow molding. This work introduces a new experimental method to examine the fluid response to Large Amplitude Oscillatory Extension (LAOE). For this, we use a microfluidic Optimized Shape Cross-slot Extensional Rheometer (OSCER) device that generates a homogeneous planar extensional flow. Programmable syringe pumps drive the flow through the OSCER geometry under oscillating or pulsatile flow conditions. We analyze the time-dependent flow field inside the OSCER by means of micro-particle image velocimetry and measure the simultaneous pressure drop to evaluate the fluid’s elastic stress response. We examine the time-dependent flow of viscoelastic dilute polymeric solutions during LAOE, covering a broad range of Weissenberg and Deborah numbers, and show how the elastic stress response of the fluids evolves in the time-dependent flow field. Our research on microfluidic LAOE flows of viscoelastic fluids advances the field of microfluidic extensional rheometry and enhances our understanding of non-Newtonian fluid dynamics.