Research Projects

Complex fluids are found in various industries and nature, such as polymers, colloids, and biological materials. They exhibit a mechanical response intermediate between ideal solid and normal fluid behavior. Accurate characterization of both elastic and viscous rheological components is crucial for a unified representation of complex fluids. These fluids are categorized as viscoplastic, elasto-viscoplastic, viscoelastic, or Generalised Newtonian fluids (GNF). Differentiating viscoplastic and GNF is challenging due to the large time scale and small length scale of rheological measurements. Measuring yield stress is even more challenging, with no widely accepted method. There are several methods in the literature but all give very different values due to long measurement times or different flow fields. To overcome this, a new method for categorizing and measuring rheological properties of complex fluids is proposed: using pressure signal propagation measurement. This method can be performed at the smallest time scale of flow but at a larger length scale, providing a unique opportunity to classify complex fluids that are difficult to identify conventionally. Understanding pressure propagation opens up the possibility of accurately measuring true static and dynamic yield stress. The pressure propagation method does not require continuous movement of the sample and long experiment duration, allowing for accurate measurement of true static yield stress. For dynamic yield stress, samples undergo predefined stress history without significant movement during measurement. The proposed method is robust and should provide accurate values for static and dynamic yield stresses.