Cavity Expansion for Measuring the Viscoelastic Behavior of Soft Materials

Cavitation Rheology (CR) is a method of measuring the local elastic modulus of soft materials; by pressure-controlled injection of a Newtonian fluid into the sample, one can identify a maximum pressure, corresponding to the onset of cavitation instability in the material [1]. This peak pressure can then be compared with theoretical predictions of the cavitation pressure to determine the elastic modulus. In this work, we expand the CR method to capture a wider range of material behaviors. Using a custom-designed setup attached to a universal testing machine, we perform volume-controlled CR experiments using incompressible fluids that are immiscible in the tested material. First, we discuss the use of this technique for materials that fracture much earlier than the strains required for capturing the cavitation instability limit. Next, we will discuss the use of cavity expansion to measure the viscoelastic response such as stress-relaxation. Lastly, we will discuss the effect of the size of the material used in the tests and how the current method can offer a novel approach for performing CR experiments with samples of different sizes.
[1] Zimberlin, Jessica A., et al. "Cavitation rheology for soft materials." Soft Matter 3.6 (2007): 763-767.