Xuan Xiangchun, Li Dongqing
Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, Ontario, Canada.
Electrophoresis. 2005 Sep;26(18):3552-60. doi: 10.1002/elps.200500298.
The electrokinetic focusing and the resultant accelerated electrophoretic motion of polystyrene particles and red blood cells were visualized in microfluidic cross-channels. The experimentally measured width of the focused stream and the measured velocity increase of particles and cells at different voltage ratios follow the proposed analytical formula within the experimental error. The attained velocity increase is insensitive to the particle size, particle property (i.e., particle or cell), and particle trajectory. By solving the electrical potential field in the cross-channel at the experimental conditions, we demonstrate that the squeezed electrical field lines in the channel intersection determine the shape of the focused stream, and the nonuniform distribution of axial electrical field strength underlies the variation of particle/cell electrophoretic velocity through the focusing region. However, the dielectrophoretic force resulting from the nonuniform electrical field in the intersection seems to push the acceleration region of particles and cells slightly in the downstream direction. We have also achieved the single particle/cell dispensing by instantly triggering an electrical pulse perpendicular to the focused particulate flow in a double-cross microchannel. The electrokinetic manipulation of particle/cell in microchannels demonstrated in this work can be used for developing integrated lab-on-a-chip devices for studies of cells.
在微流体交叉通道中观察到了聚苯乙烯颗粒和红细胞的电动聚焦以及由此产生的加速电泳运动。在实验误差范围内，实验测得的聚焦流宽度以及在不同电压比下测得的颗粒和细胞速度增加符合所提出的解析公式。所达到的速度增加对颗粒大小、颗粒性质（即颗粒或细胞）以及颗粒轨迹不敏感。通过求解实验条件下交叉通道中的电势场，我们证明了通道交叉处挤压的电场线决定了聚焦流的形状，而轴向电场强度的不均匀分布是颗粒/细胞电泳速度在聚焦区域变化的基础。然而，交叉处不均匀电场产生的介电泳力似乎会将颗粒和细胞的加速区域稍微向下游方向推动。我们还通过在双交叉微通道中瞬间触发垂直于聚焦颗粒流的电脉冲实现了单颗粒/细胞分配。这项工作中展示的微通道中颗粒/细胞的电动操作可用于开发用于细胞研究的集成芯片实验室装置。
