Huang Hao, Ou-Yang H Daniel
Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, USA.
Emulsion Polymers Institute, Lehigh University, Bethlehem, PA, USA.
Electrophoresis. 2017 Jun;38(12):1609-1616. doi: 10.1002/elps.201700049. Epub 2017 Apr 20.
Dielectrophoresis (DEP) has been widely used to manipulate nanoparticles in microfluidic applications. However, determination of the DEP force of nanoparticles by theoretical models is not easy due to complications caused by the polarization of electrical double layer. Additionally, there is a lack of suitable experimental techniques to quantify the DEP force of nanoparticles. This article reports a statistical mechanics-based experimental method to determine the DEP potential energy of a single particle by measuring the equilibrium number density of particles in a DEP force field. Results show that at high frequencies, the measured potentials agree with the Maxwell-Wagner-O'Konski (MWO) theory. At frequencies lower than the crossover frequency (ω ), the measured potential values are larger than MWO theory's predictions. When an effective particle radius (particle radius plus Debye length) is used to replace the particle radius, MWO theory fits better with the measured potentials on both sides of ω . Also, the measured ω was found inversely proportional to the effective particle radius, which agrees with MWO theory. The new DEP potential spectroscopy is not limited to the size or shape of particles, opening doors to investigate the DEP response functions of quantum dots and proteins in an alternating current electric field.
介电泳（DEP）已广泛应用于微流体应用中对纳米颗粒的操控。然而，由于电双层极化所导致的复杂性，通过理论模型来确定纳米颗粒的介电泳力并非易事。此外，还缺乏合适的实验技术来量化纳米颗粒的介电泳力。本文报道了一种基于统计力学的实验方法，通过测量介电泳力场中颗粒的平衡数密度来确定单个颗粒的介电泳势能。结果表明，在高频下，测量得到的势能与麦克斯韦 - 瓦格纳 - 奥康斯基（MWO）理论相符。在低于交叉频率（ω）的频率下，测量得到的势能值大于MWO理论的预测值。当使用有效颗粒半径（颗粒半径加上德拜长度）来代替颗粒半径时，MWO理论在ω两侧与测量得到的势能拟合得更好。此外，发现测量得到的ω与有效颗粒半径成反比，这与MWO理论一致。新的介电泳势能光谱法不限于颗粒的尺寸或形状，为研究量子点和蛋白质在交变电场中的介电泳响应函数打开了大门。
