[Electrophoresis] SA novel dielectrophoresis potential spectroscopy for colloidal nanoparticles
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 (EDL). Additionally, there is a lack of suitable experimental techniques to quantify the DEP force of nanoparticles. This paper 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 (ωco), 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 ωco. Also, the measured ωco 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 AC electric field.
Hao Huang, H. Daniel Ou-Yang Accepted manuscript online: 29 March 2017 DOI: 10.1002/elps.201700049