Dielectrophoresis force spectroscopy for colloidal nanoparticles (Conference Presentation)

Abstract

Dielectrophoresis (DEP) is the motion of colloidal particles in an inhomogeneous electric field. Accurate determination of dielectrophoresis (DEP) force is important for lab-on-a-chip applications. However current DEP force spectroscopy methods are not suitable for accurately measuring the DEP force for sub-micron particles. A new and facile method is developed to measure the DEP force as a function of the frequency of the electric field for nanoparticles by an ensemble analysis approach. Using the principle of Boltzmann distribution of the concentration of non-interacting particles in a DEP potential field, the new method determines the DEP potential field from the measured time-averaged concentration distribution of fluorescently labeled nanoparticle in the DEP field by confocal fluorescence microscopy. Frequency dependent DEP force is determined by the negative gradient of the DEP potential created by the electric field across gold-film electrodes in a microfluidic setting. This approach is capable of measuring forces at the level of one femto Newton for particles with diameters in the range of 63 nm to 410 nm.