A novel optically driven electrokinetic technique for manipulating nanoparticles

We utilize a simple parallel electrode setup on which intense holographic optical landscapes are shone. Intense optical illumination creates high local gradients in the dielectric properties of the fluid, which in the presence of an electric field results in a fluid body force. This leads to the creation of toroidal microvortices, which aid the particle concentration process. Fluid drag aiding low frequency AC electrokinetic forces leads to an aggregation of particles on the illuminated regions of the electrode surface. With a fine balance of these forces, we show that such optically driven electrokinetic mechanisms can capture and aggregate nanoparticles (50nm and 100 nm). Particle aggregation is a function of the AC frequency and by using fluorescent particles we characterize the technique as a function of the applied AC frequency. Relatively low optical powers (~20 mW) are utilized in this technique.