Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, Florida 32310, United States.
Department of Mechanical Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, Florida 32310, United States.
Langmuir. 2023 Jun 6;39(22):7672-7683. doi: 10.1021/acs.langmuir.3c00483. Epub 2023 May 23.
Measuring the surface tension of yield stress fluids has remained a critical challenge due to limitations of the traditional tensiometry techniques. Here, we overcome those limits and successfully measure the surface tension and mechanical properties of a model yield stress fluid based on Carbopol gels via a needle-induced cavitation (NIC) technique. Our results indicate that the surface tension is approximately 70 ± 3 mN/m, and is independent of the rheology of yield stress fluid over a wide range of yield stress values σ = 0.5-120 Pa. In addition, we demonstrate that a Young modulus smaller than < 1 kPa can be successfully measured for Carbopol gels with NIC method. Finally, we present a time-resolved flow structure around the cavity in a host of yield stress fluids, and assess the impact of fluid rheology on the detailed form of flow around the cavity. Interestingly, prior to the critical point associated with cavitation, the yield stress fluid is weakly deformed suggesting that the measured surface tension data reflect the near equilibrium values. Beyond the critical point, the yield stress fluid experiences a strong flow that is controlled by both the critical pressure and the non-Newtonian rheology of the yield stress fluid.
由于传统张力测量技术的限制，测量屈服应力流体的表面张力仍然是一个关键挑战。在这里，我们克服了这些限制，成功地通过针诱导空化（NIC）技术测量了基于 Carbopol 凝胶的模型屈服应力流体的表面张力和力学性能。我们的结果表明，表面张力约为 70±3 mN/m，并且在广泛的屈服应力值 σ=0.5-120 Pa 范围内与屈服应力流体的流变学无关。此外，我们证明了对于 NIC 方法的 Carbopol 凝胶，可以成功测量小于 <1 kPa 的杨氏模量。最后，我们展示了一系列屈服应力流体中腔周围的时变流结构，并评估了流体流变学对腔周围流详细形式的影响。有趣的是，在与空化相关的临界点之前，屈服应力流体被弱变形，这表明测量的表面张力数据反映了近平衡值。超过临界点后，屈服应力流体经历由临界压力和屈服应力流体的非牛顿流变控制的强烈流动。
