Two-particle dynamics on an electrode in ac electric fields.
Two-particle dynamics on an electrode in ac electric fields.
复制标题
交流电场中电极上的双粒子动力学。
DOI：
10.1016/s0001-8686(01)00078-1
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发表时间：
2002
影响因子：
15.6
通讯作者：
J. L. Anderson
中科院分区：
文献类型：
--
作者：
Junhyung Kim;S. Guelcher;S. Garoff;J. L. Anderson
用光学显微镜和图像分析技术测量了沉积在电极上的直径为9.7 μm的带负电荷乳胶粒子对之间的相对运动。在约30 V cm-1的均方根场下，两个粒子以低于500 Hz的频率朝向彼此移动，但在1000 Hz时分离。在聚合的情况下，有几个有趣的特征。首先，当一对的中心到中心的分离最初是6个粒子半径或更远时，在粒子开始向彼此移动之前，观察到数十秒的瞬时“潜伏”期。第二，两个粒子从来没有接触过，而是在很长一段时间里，这对粒子之间保持着一个大约等于粒子半径一半的固定间隙。对于三个或更多个颗粒的簇的聚集，也观察到颗粒之间的这种固定间隙。最后，一对粒子的接近率随着频率的增加而降低。与直流场相比，在交流中需要更大的场来移动粒子;在30 Hz时，交流场必须比直流场大130倍才能达到相同的接近速率。利用直流场与交流场中粒子协同运动的定性和定量差异，应该能够通过在这两种模式之间交替来重新定位粒子。我们证明了同一对粒子可以在低频（100或200 Hz）下聚集在一起，然后在高频（1000 Hz）下分离。
The relative motion between pairs of negatively charged latex particles 9.7 μm in diameter and deposited on an electrode was measured by optical microscopy and image analysis. At an rms field of approximately 30 V cm−1, the two particles moved toward each other at frequencies below 500 Hz, but they separated at 1000 Hz. In the cases of aggregation, there are several interesting characteristics. First, when the center-to-center separation of a pair was initially 6 particle radii or more apart, a transient ‘incubation’ period of tens of seconds was observed before the particles began to move toward each other. Second, the two particles never came into contact, rather at long times the pair maintained a stationary gap between them equal to approximately one-half the particle radius. This stationary gap between particles was also observed for the aggregation of clusters of three or more particles. Finally, the rate of approach for a pair of particles decreased as the frequency increased. Larger fields are required to move particles together in ac compared to dc fields; at 30 Hz the ac field must be 130 times greater than the dc field to achieve the same rate of approach. Taking advantage of the qualitative and quantitative differences of the cooperative motion of particles in dc vs. ac fields, one should be able to re-position particles by alternating between these two modes. We demonstrated that the same pair of particles can be brought together at low frequency (100 or 200 Hz) and then separated at high frequency (1000 Hz).