Nat Mater. 2010 Mar;9(3):220-4. doi: 10.1038/nmat2627. Epub 2010 Jan 31.
Suspensions are of wide interest and form the basis for many smart fluids. For most suspensions, the viscosity decreases with increasing shear rate, that is, they shear thin. Few are reported to do the opposite, that is, shear thicken, despite the longstanding expectation that shear thickening is a generic type of suspension behaviour. Here we resolve this apparent contradiction. We demonstrate that shear thickening can be masked by a yield stress and can be recovered when the yield stress is decreased below a threshold. We show the generality of this argument and quantify the threshold in rheology experiments where we control yield stresses arising from a variety of sources, such as attractions from particle surface interactions, induced dipoles from applied electric and magnetic fields, as well as confinement of hard particles at high packing fractions. These findings open up possibilities for the design of smart suspensions that combine shear thickening with electro- or magnetorheological response.
悬浮液具有广泛的应用，是许多智能流体的基础。对于大多数悬浮液，其粘度随剪切速率的增加而降低，也就是说，它们具有剪切变稀的特性。尽管人们早就期望剪切增稠是一种普遍的悬浮液行为类型，但很少有报道称其具有相反的特性，即剪切变稠。在这里，我们解决了这个明显的矛盾。我们证明，屈服应力可以掩盖剪切增稠现象，并且当屈服应力降低到阈值以下时，可以恢复剪切增稠现象。我们展示了这个论点的普遍性，并在流变学实验中对其进行了量化，我们在实验中控制了各种来源产生的屈服应力，如颗粒表面相互作用产生的吸引力、外加电场和磁场产生的诱导偶极矩，以及在高填充分数下硬颗粒的受限。这些发现为设计智能悬浮液提供了可能性，这种悬浮液将剪切增稠与电流变或磁流变响应结合在一起。
