This paper describes the behavior of particles in a deterministic lateral displacement (DLD) separation device with DC and AC electric fields applied orthogonal to the fluid flow. As proof of principle, we demonstrate tunable microparticle and nanoparticle separation and fractionation depending on both particle size and zeta potential. DLD is a microfluidic technique that performs size-based binary separation of particles in a continuous flow. Here, we explore how the application of both DC and AC electric fields (separate or together) can be used to improve separation in a DLD device. We show that particles significantly smaller than the critical diameter of the device can be efficiently separated by applying orthogonal electric fields. Following the application of a DC voltage, Faradaic processes at the electrodes cause local changes in medium conductivity. This conductivity change creates an electric field gradient across the channel that results in a nonuniform electrophoretic velocity orthogonal to the primary flow direction. This phenomenon causes particles to focus on tight bands as they flow along the channel countering the effect of particle diffusion. It is shown that the final lateral displacement of particles depends on both particle size and zeta potential. Experiments with six different types of negatively charged particles and five different sizes (from 100 nm to 3 μm) and different zeta potential demonstrate how a DC electric field combined with AC electric fields (that causes negative-dielectrophoresis particle deviation) could be used for fractionation of particles on the nanoscale in microscale devices.

中文翻译：

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将直流和交流电场与确定性的横向位移相结合，用于分离微米和纳米颗粒。

本文介绍了在确定性横向位移（DLD）分离设备中颗粒的行为，该设备在与流体流动正交的方向上施加了DC和AC电场。作为原理的证明，我们证明了可调谐的微粒和纳米微粒的分离和分级取决于粒径和Zeta电位。DLD是一种微流体技术，可在连续流中执行基于尺寸的颗粒二元分离。在这里，我们探索如何同时使用直流和交流电场（分离的或共同的）来改善DLD设备中的分离。我们表明，可以通过施加正交电场有效地分离出明显小于设备临界直径的颗粒。施加直流电压后，电极上的法拉第过程导致介质电导率的局部变化。这种电导率变化会在整个通道上产生电场梯度，从而导致正交于主流方向的电泳速度不均匀。当颗粒沿着通道流动时，这种现象会导致颗粒集中在紧密的条带上，从而抵消了颗粒扩散的影响。结果表明，颗粒的最终横向位移取决于颗粒大小和ζ电势。用六种不同类型的带负电粒子和五种不同大小（从100 nm到3μm）和不同的Zeta电势进行的实验表明，如何将直流电场和交流电场（导致负介电电泳粒子偏离）结合起来进行分馏微型设备中纳米级颗粒的数量。