Pairwise frictional profile between particles determines discontinuous shear thickening transition in non-colloidal suspensions.
Pairwise frictional profile between particles determines discontinuous shear thickening transition in non-colloidal suspensions.
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DOI：
10.1038/ncomms15633
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发表时间：
2017-05-31
影响因子：
16.6
通讯作者：
Colin A
中科院分区：
文献类型：
--
作者：
Comtet J;Chatté G;Niguès A;Bocquet L;Siria A;Colin A
被剪切的悬浮液经历粘度的急剧变化的过程被称为不连续剪切增稠。尽管在宏观层面上已经得到了很好的描述，但在这种转变中发挥作用的微观机制仍然知之甚少。在这里，通过开发新的实验程序的基础上石英音叉原子力显微镜，我们测量接近对的聚氯乙烯和玉米淀粉颗粒在溶剂中的成对摩擦配置文件。我们报告了一个明确的过渡，从低摩擦制度，其中对颗粒支持有限的正常负载，而相互作用纯粹流体动力学，到高摩擦制度的特点是硬排斥颗粒之间的接触和滑动摩擦。重要的是，我们表明，进入摩擦制度在纳米级所需的正应力匹配的临界应力，在该临界应力下发生剪切增稠宏观悬浮液。我们的实验桥接了纳米尺度和宏观尺度，并提供了长期需要的摩擦力在不连续剪切增稠中的作用的证明。剪切增稠的特征在于颗粒的液体悬浮液受到应力可逆地固化。在这里，Comtet等人表明，剪切增稠发生在从润滑接触到摩擦接触的过渡处，在单颗粒水平上，这可能与宏观流变学的变化有关。
The process by which sheared suspensions go through a dramatic change in viscosity is known as discontinuous shear thickening. Although well-characterized on the macroscale, the microscopic mechanisms at play in this transition are still poorly understood. Here, by developing new experimental procedures based on quartz-tuning fork atomic force microscopy, we measure the pairwise frictional profile between approaching pairs of polyvinyl chloride and cornstarch particles in solvent. We report a clear transition from a low-friction regime, where pairs of particles support a finite normal load, while interacting purely hydrodynamically, to a high-friction regime characterized by hard repulsive contact between the particles and sliding friction. Critically, we show that the normal stress needed to enter the frictional regime at nanoscale matches the critical stress at which shear thickening occurs for macroscopic suspensions. Our experiments bridge nano and macroscales and provide long needed demonstration of the role of frictional forces in discontinuous shear thickening. Shear thickening characterizes liquid suspensions of particles that reversibly solidify subject to stress. Here, Comtet et al. show that shear thickening occurs at the transition from lubricated contacts to frictional contacts at a single-particle level, which can be linked to the change in macroscopic rheology.