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 25 capacitive pressure sensors (of surface $4.5\times 4.5{\mathrm{mm}}^2$ each) built together in a $5\times 5$ regular array. The sensor array is used to obtain a mapping of the normal stresses in complex fluids, which dramatically extends the capability of the rheometer. We demonstrate this with three examples. First, a pressure profile is reconstructed in a polymer solution, which enables 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 pressures can also be measured. Finally, we focus on the normal stress fluctuations that extend both spatially and temporally in a shear-thickening suspension of cornstarch particles. We evidence the presence of 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.

中文翻译：

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用于复杂流体中法向应力测量的新型压力传感器阵列

介绍了一种新的压力传感器阵列，位于标准扭转流变仪的底板上。它由独特的压电电容聚合物泡沫制成，由 25 个电容式压力传感器（表面$4.5\times 4.5{\mathrm{毫米}}^2$ 每个）一起构建在一个 $5\times 5$常规数组。传感器阵列用于获取复杂流体中法向应力的映射，这极大地扩展了流变仪的功能。我们用三个例子来证明这一点。首先，在聚合物溶液中重建压力分布，从而能够同时测量第一和第二法向应力差$N_1$ 和 $N_2$，精度为 2 Pa。在第二部分中，我们展示了也可以测量负压。最后，我们关注在玉米淀粉颗粒的剪切增稠悬浮液中在空间和时间上延伸的法向应力波动。我们证明存在非常规律地旋转的独特异质性。除了低成本和高通用性之外，这些传感器还展示了它们在精细表征粘度流动中的法向应力方面的潜力。