Experimental Challenges of Shear Rheology: How to Avoid Bad Data
Experimental Challenges of Shear Rheology: How to Avoid Bad Data
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DOI：
10.1007/978-1-4939-2065-5_6
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发表时间：
2015-01-01
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影响因子：
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通讯作者：
Caretta, Lucas M.
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文献类型：
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作者：
Ewoldt, Randy H.;Johnston, Michael T.;Caretta, Lucas M.
当材料实际上不具有剪切变稀、剪切增稠和粘弹性响应时，各种测量伪影可被归咎于对这些特性的误解。生物材料的柔软性和活性通常会放大实验流变测量的挑战。流变材料函数的理论定义基于简单变形场中的应力、应变和应变率分量。实际上，通常测量样品边界处的载荷和位移，并且真实应力和应变的计算可能受到仪器分辨率、仪器惯性、样品惯性、边界效应和体积效应的阻碍。在这里，我们讨论了在软，水基，甚至活的生物复杂流体的背景下测量剪切材料功能的这些常见挑战。我们讨论的技术，以确定和尽量减少实验误差和推动旋转剪切流变仪的实验极限。使用两个极端的案例研究：超软水性聚合物/纤维网络（盲鳗防御凝胶）和积极游泳悬浮液的微藻（杜氏藻primolecta）。
A variety of measurement artifacts can be blamed for misinterpretations of shear thinning, shear thickening, and viscoelastic responses, when the material does not actually have these properties. The softness and activity of biological materials will often magnify the challenges of experimental rheological measurements. The theoretical definitions of rheological material functions are based on stress, strain, and strain-rate components in simple deformation fields. In reality, one typically measures loads and displacements at the boundaries of a sample, and the calculation of true stress and strain may be encumbered by instrument resolution, instrument inertia, sample inertia, boundary effects, and volumetric effects. Here we discuss these common challenges in measuring shear material functions in the context of soft, water-based, and even living biological complex fluids. We discuss techniques for identifying and minimizing experimental errors and for pushing the experimental limits of rotational shear rheometers. Two extreme case studies are used: an ultrasoft aqueous polymer/fiber network (hagfish defense gel) and an actively swimming suspension of microalgae (Dunaliella primolecta).