A new pressure sensor array for local normal stress measurement in complex fluids

Abstract

A new pressure sensor array, positioned on the bottom plate of a standard torsional rheometer is presented. It is built from a unique piezo-capacitive polymeric foam, and consists of twenty-five capacitive pressure sensors (of surface 4.5$\times$4.5 mm${}^2$ each) built together in a 5$\times$5 regular array. The sensor array is used to obtain a local mapping of the normal stresses in complex fluids, which dramatically extends the capability of the rheometer. We demonstrate this with three examples. First, the pressure profile is reconstructed in a polymer solution, which enable the simultaneous measurement of the first and the second normal stress differences $N_1$ and $N_2$, with a precision of 2 Pa. In a second part, we show that negative normal stresses can also be detected. Finally, we focus on the normal stress fluctuations that extend both spatially and temporally ina shear-thickening suspension of cornstarch particles. We evidence the presence of local a unique heterogeneity rotating very regularly. In addition to their low-cost and high versatility, the sensors show here their potential to finely characterize the normal stresses in viscosimetric flows.

arXiv comment5 figures

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Cited by in corpus (7)

• Structure of propagating high stress fronts in a shear thickening suspension
• Shear-thickening in presence of adhesive contact forces: the singularity of cornstarch
• Stress-stress Correlations Reveal Force Chains in Gels
• Optimising non-Newtonian fluids for impact protection of laminates
• Non-monotonic Rheology and Stress Heterogeneity in confined Granular suspensions
• Emergence of a hexagonal pattern in shear-thickening suspensions under orbital oscillations
• Pressure shifts in pulsatile shear: A microfluidic method to probe the normal stress response of complex fluids