Nudurupati Sai, Janjua Mohammad, Aubry Nadine, Singh Pushpendra
Department of Mechanical Engineering, New Jersey Institute of Technology, Newark, NJ, USA.
Electrophoresis. 2008 Mar;29(5):1164-72. doi: 10.1002/elps.200700676.
We propose to use an externally applied uniform electric field to alter the distribution of particles on the surface of a drop immersed in another immiscible liquid. Specifically, we seek to generate well-defined concentrated regions at the drop surface while leaving the rest of the surface particle free. Experiments show that when the dielectric constant of the drop is greater than that of the ambient liquid the particles for which the Clausius-Mossotti factor is positive move along the drop surface to the two poles of the drop. Particles with a negative Clausius-Mossotti factor, on the other hand, move along the drop surface to form a ring near the drop equator. The opposite takes place when the dielectric constant of the drop is smaller than that of the ambient liquid, namely particles for which the Clausius-Mossotti factor is positive form a ring near the equator while those for which such a factor is negative move to the poles. This motion is due to the dielectrophoretic force that acts upon particles because the electric field on the surface of the drop is nonuniform, despite the uniformity of the applied electric field. Experiments also show that when small particles collect at the poles of a deformed drop the electric field needed to break the drop is smaller than without particles. These phenomena could be useful to concentrate particles at a drop surface within well-defined regions (poles and equator), separate two types of particles at the surface of a drop or increase the drop deformation to accelerate drop breakup.
我们提议使用外部施加的均匀电场来改变浸没在另一种不混溶液体中的液滴表面上颗粒的分布。具体而言，我们试图在液滴表面产生定义明确的浓缩区域，而使表面的其余部分没有颗粒。实验表明，当液滴的介电常数大于周围液体的介电常数时，克劳修斯 - 莫索蒂因子为正的颗粒会沿着液滴表面移动到液滴的两极。另一方面，克劳修斯 - 莫索蒂因子为负的颗粒会沿着液滴表面移动，在液滴赤道附近形成一个环。当液滴的介电常数小于周围液体的介电常数时，情况则相反，即克劳修斯 - 莫索蒂因子为正的颗粒在赤道附近形成一个环，而该因子为负的颗粒则移动到两极。这种运动是由于尽管施加的电场是均匀的，但液滴表面的电场不均匀，从而作用在颗粒上的介电泳力所致。实验还表明，当小颗粒聚集在变形液滴的两极时，使液滴破裂所需的电场比没有颗粒时要小。这些现象可能有助于将颗粒集中在液滴表面的定义明确的区域（两极和赤道）内，在液滴表面分离两种类型的颗粒，或者增加液滴变形以加速液滴破裂。
