极性分子型电流变液

Polar molecule type electrorheological fluids

电流变液在电场作用下软硬连续可调的奇特性质具有广泛和重要的应用价值。传统电流变液是基于颗粒极化产生的相互作用,根据介电理论预测,其剪切屈服强度的上限约为10kPa。电流变液被发明50年来,阻碍其应用的主要原因是剪切强度低。近年来发明的"极性分子型电流变液"是一类新型电流变液,其屈服强度比传统电流变液大一个数量级以上,且与电场强度呈线性关系,这一点和传统电流变液中的平方关系也明显不同。文章作者提出了极性分子在颗粒间强局域电场中的取向并与极化电荷作用的模型,成功地解释了观察到的实验现象。根据这一原理,有可能制备出屈服强度高达MPa的电流变液。

In electrorheological （ER） fluids the shear strength or hardness can be continuously and rapidly tuned by applying an electric field, thus these media promise significant applications in a wide range of industries. Ordinary ER fluids operate on the basis of mutual interaction among the polarized particles, consequently the max- imum yield stress available, according to the dielectric theory, is only about lOkPa. This low yield stress has deferred the implementation of ER effects for half a century since its discovery. In recent years we succeeded in making a variety of new ER fluids, known as polar molecule dominated ER fluids, in which the yield stress can be raised by an order of magnitude or even more. The yield stress shows a linear dependence on the electric field, which differs from the quadratic relation for ordinary ER fluids. We postulate that this extraordinarily large effect originates in the polar molecules aligned by the strong local field among particles, i. e. , via the polar molecule - polarization charge interaction. This model can explain the experimental phenomena observed in polar molecule dominated ER fluids, and it also promises the possibility of obtaining a yield stress on the order of MPa through exploitation of this mechanism.