West J Hunter, Mondal Tonoy K, Williams Stuart J
Department of Mechanical Engineering, University of Louisville, Louisville, Kentucky, USA.
Electrophoresis. 2024 Sep 2. doi: 10.1002/elps.202400051.
The frequency dependence of electrokinetic particle trapping using large-area (>mm) conductive carbon nanofiber (CNF) mat electrodes is investigated. The fibers provide nanoscale geometric features for the generation of high electric field gradients, which is necessary for particle trapping via dielectrophoresis (DEP). A device was fabricated with an array of microfluidic wells for repeated experiments; each well included a CNF mat electrode opposing an aluminum electrode. Fluorescent microspheres (1 µm) were trapped at various electric field frequencies between 30 kHz and 1 MHz. Digital images of each well were analyzed to quantify particle trapping. DEP trapping by the CNF mats was greater at all tested frequencies than that of the control of no applied field, and the greatest trapping was observed at a frequency of 600 kHz, where electrothermal flow is more significantly weakened than DEP. Theoretical analysis and measured impedance spectra indicate that this result was due to a combination of the frequency dependence of DEP and capacitive behavior of the well-based device.
研究了使用大面积（>毫米）导电碳纳米纤维（CNF）垫电极进行电动粒子捕获的频率依赖性。这些纤维提供了纳米级几何特征，以产生高电场梯度，这是通过介电泳（DEP）捕获粒子所必需的。制造了一种带有微流体孔阵列的装置用于重复实验；每个孔都包括一个与铝电极相对的CNF垫电极。在30kHz至1MHz的各种电场频率下捕获荧光微球（1μm）。分析每个孔的数字图像以量化粒子捕获。在所有测试频率下，CNF垫的DEP捕获都比无外加电场的对照更大，并且在600kHz频率下观察到最大捕获，此时电热流比DEP更显著地减弱。理论分析和测量的阻抗谱表明，该结果是由于DEP的频率依赖性和基于孔的装置的电容性行为的组合。
