Optically Modulated Electrokinetic Manipulation and Concentration of Colloidal Particles near an Electrode Surface
Optically Modulated Electrokinetic Manipulation and Concentration of Colloidal Particles near an Electrode Surface
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DOI：
10.1021/la904661y
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发表时间：
2010-04-06
期刊：
影响因子：
3.9
通讯作者：
Wereley, Steven T.
中科院分区：
文献类型：
--
作者：
Kumar, Aloke;Kwon, Jae-Sung;Wereley, Steven T.
我们研究了最近证明的AC电动技术的操纵和浓度的胶体粒子在电极表面上。该技术使用氧化铟锡（ITO）为基础的平行板电极上高度本地化的红外（1064纳米）激光照射。我们表明，高度局部化的激光照明导致高度不均匀的加热的电极基板，这反过来又驱动一个微涡旋，导致在一个快速运输的颗粒朝向照明网站。数以百计的聚苯乙烯颗粒，直径范围从2.0到0.1 μ m，悬浮在一个低电导率的解决方案（2.0 mS/m），可以聚集在选定的位置上的电极通过激活激光照射在适当的交流频率。随后失活的激光照射导致粒子散射，我们探索这种动力学行为为1.0 μ m的颗粒使用Delaunay镶嵌和高速摄像。我们建立了阻力从微涡旋的行为对排斥力，随着交流频率的增加而减少，以创建稳定的粒子簇。此外，实验上，我们表明，这种粒子捕获技术的特点是由一个临界频率：在该频率下，捕获的胶体粒子簇变得不稳定，颗粒被带走到散装的微涡旋。对于相似颗粒，该临界频率随着颗粒直径的减小而增加。对于0.1 μ m的颗粒，在不同的AC频率下的聚集的比较是通过聚集的荧光强度分布的比较来实现的。
We study a recently demonstrated AC electrokinetic technique for manipulation and concentration of colloidal particles on an electrode surface. The technique uses indium tin oxide (ITO)-based parallel-plate electrodes on which highly localized infrared (1064 nun) laser illumination is shone. We show that the highly localized laser illumination leads to a highly nonuniform heating of the electrode substrate, which in turn drives an electrothermal microvortex resulting in a rapid transport of particles toward the illuminated site. Hundreds of polystyrene particles, with diameters ranging from 2.0 to 0.1 mu m, suspended in a low conductivity solution (2.0 mS/m) could be aggregated at selected locations on the electrode by activating the laser illumination at suitable AC frequencies. Subsequent deactivation of the laser illumination causes the particles to scatter, and we explore this dynamical behavior for 1.0 mu m particles using Delaunay tessellations and high-speed videography. We establish that drag from the electrothermal microvortex acts against a repulsive force, which decreases with increasing AC frequency; to create stable particle clusters. Moreover, experimentally we show that this particle capturing technique can be characterized by a critical frequency: a frequency at which the captured colloidal particle cluster becomes unstable and particles are carried away into the bulk by the electrothermal microvortex. This critical frequency increases with decreasing particle diameter for similar particles. For 0.1 mu m particles, comparison of aggregation at different AC frequencies is achieved by the comparison of fluorescent intensity profiles of the aggregations.