Lele Pushkar P, Mittal Manish, Furst Eric M
Department of Chemical Engineering and Center for Molecular and Engineering Thermodynamics, University of Delaware, Newark, DE, USA.
Langmuir. 2008 Nov 18;24(22):12842-8. doi: 10.1021/la802225u. Epub 2008 Oct 25.
We study the transition of ordered structures to disordered bands and vortices in colloidal suspensions subjected to AC electric fields. We map the critical frequencies and field biases at which particles form disordered bands and vortices. These results are interpreted based on the trajectory dynamics of particle pairs using blinking optical tweezers. Under conditions that vortices are observed, individual particle pairs rotate out of alignment with the field. The direction and magnitude of these interactions determine the orientation and average angular velocity of the band revolution. Increasing the frequency of the electric field reduces the anomalous rotation of the particles pairs, consistent with the frequency dependence of the suspension order-to-disorder transition. This anomalous rotation is consistent with a torque on doublets generated by the mutual polarization of particles and phase lag of the induced dipoles.
我们研究了在交变电场作用下胶体悬浮液中有序结构向无序带和涡旋的转变。我们绘制了粒子形成无序带和涡旋时的临界频率和场偏置。利用闪烁光镊，基于粒子对的轨迹动力学对这些结果进行了解释。在观察到涡旋的条件下，单个粒子对会旋转至与电场方向不一致。这些相互作用的方向和大小决定了带旋转的方向和平均角速度。增加电场频率会降低粒子对的反常旋转，这与悬浮液有序 - 无序转变的频率依赖性一致。这种反常旋转与由粒子的相互极化和感应偶极子的相位滞后产生的双联体上的扭矩一致。
