We introduce herein an efficient microfluidic approach for continuous transport and localized collection of nanoparticles via hybrid electrokinetics, which delicately combines linear and nonlinear electrokinetics driven by a composite DC‐biased AC voltage signal. The proposed technique utilizes a simple geometrical structure, in which one or a series of metal strips serving as floating electrode (FE) are attached to the substrate surface and arranged in parallel between a pair of coplanar driving electrodes (DE) in a straight microchannel. On application of a DC‐biased AC electric field across the channel, nanoparticles can be transported continuously by DC bulk electroosmotic flow, and then trapped selectively onto the metal strips due to AC‐field induced‐charge electrokinetic (ICEK) phenomenon, which behaves as counter‐rotating micro‐vortices around the ideally polarizable surfaces of FE. Finite‐element simulation is carried out by coupling the dual‐frequency electric field, flow field and sample mass transfer in sequence, for guiding a practical design of the microfluidic nanoparticle concentrator. With the optimal device geometry, the actual performance of the technique is investigated with respect to DC bias, AC voltage amplitude, and field frequency by using both latex nanospheres (∼500 nm) and BSA molecules (∼10 nm). Our experimental observation indicates nanoparticles are always enriched into a narrow bright band on the surface of each FE, and a horizontal concentration gradient even emerges in the presence of multiple metal strips, which therefore permits localized analyte enrichment. The proposed trapping method is supposed to guide an elaborate design of flexible electrokinetic frameworks embedding FE for continuous‐flow analyte manipulation in modern microfluidic systems.

中文翻译：

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微流体中由混合电动学驱动的连续流动纳米粒子捕获

我们在此介绍了一种通过混合电动学连续传输和局部收集纳米粒子的高效微流体方法，该方法巧妙地结合了由复合直流偏置交流电压信号驱动的线性和非线性电动学。所提出的技术利用简单的几何结构，其中一个或一系列用作浮动电极 (FE) 的金属条附着在基板表面，并平行排列在直微通道中的一对共面驱动电极 (DE) 之间。在跨通道施加直流偏置交流电场时，纳米粒子可以通过直流体电渗流连续传输，然后由于交流场感应电荷电动（ICEK）现象而选择性地捕获到金属条上，它表现为围绕 FE 理想极化表面的反向旋转微涡旋。通过依次耦合双频电场、流场和样品传质进行有限元模拟，以指导微流控纳米粒子浓缩器的实际设计。借助最佳器件几何形状，通过使用乳胶纳米球 (~500 nm) 和 BSA 分子 (~10 nm) 研究该技术在直流偏置、交流电压幅度和场频率方面的实际性能。我们的实验观察表明，纳米粒子总是富集在每个 FE 表面的窄亮带中，甚至在存在多个金属条的情况下也会出现水平浓度梯度，因此可以实现局部分析物富集。