Two-dimensional crystallization of microspheres by a coplanar AC electric field
Two-dimensional crystallization of microspheres by a coplanar AC electric field
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DOI：
10.1021/la035812y
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发表时间：
2004-03-16
期刊：
影响因子：
3.9
通讯作者：
Velev, OD
中科院分区：
文献类型：
--
作者：
Lumsdon, SO;Kaler, EW;Velev, OD
交变电场诱导的粒子间相互作用和粒子间相互作用可以方便地用于胶体晶体的片上组装。两个共面电极之间的毫米大小的间隙在这里使用组装从乳胶或二氧化硅微球悬浮液的二维晶体。当施加AC电压时，颗粒在电极之间的表面上积聚并结晶。光衍射和显微观察表明，六方晶体总是以一个轴沿着场的方向取向。当磁场关闭时，粒子会分解，这个过程可以重复多次。所有连续形成的晶体的衍射图案都是相同的。该组装是由依赖于电场梯度的力驱动的，并且提出了一个涉及介电电泳和诱导偶极链的组合的模型。大的二维晶体的组织允许在粒子系综的静电相互作用的表征。该过程可以通过场强、频率和液体介质的粘度来控制。它可以用来制造基本的光学开关，或者用来分离不同大小的颗粒混合物。
The particle-field and particle-particle interactions induced by alternating electric fields can be conveniently used for on-chip assembly of colloidal crystals. Two coplanar electrodes with a millimeter-sized gap between them are used here to assemble two-dimensional crystals from suspensions of either latex or silica microspheres. When an AC voltage is applied, the particles accumulate and crystallize on the surface between the electrodes. Light diffraction and microscopic observations demonstrate that the hexagonal crystal is always oriented with one axis along the direction of the field. The particles disassemble when the field is turned off, and the process can be repeated many times. The diffraction patterns from all consecutively formed crystals are identical. This assembly is driven by forces that depend on the electric field gradient, and a model is proposed involving a combination of dielectrophoresis and induced dipole chaining. The organization of large two-dimensional crystals allows characterization of the electrostatic interactions in the particle ensembles. The process can be controlled via the field strength, the frequency, and the viscosity of the liquid media. It could be used to make rudimentary optical switches or to separate mixtures of particles of different sizes.