Trapping of Nanoparticles with Dielectrophoretic Nano-Probes

Silver gallium nano-probes have been used as dielectrophoretic electrodes to capture sub-micron colloids.  The silver gallium nano-probes were fabricated using a unique self-assembly method.  The nano-probes are crystalline structures that self-assemble at room temperature and pressure when thin films of elemental silver are introduced to micro-spheres of elemental gallium. The direction of the nano-probe assembly can be controlled by the geometry of the substrate on which they are grown.  The diameters of the nano-probes were measured to be approximately 100-500 nm.  Using nano-probes and ITO coverslips as electrodes, sub-micron colloids suspended in DI water and aqueous KCl were attracted and repelled using positive and negative dielectrophoretic forces at voltages of less than 1 V_RMS.  Positive DEP forces successfully captured 200 nm fluorescent polystyrene particles as well as gold colloidal quantum dots as small as 5 nm in diameter.  Negative DEP forces were observed acting on fluorescent sub-micron polystyrene particles in solutions of various conductivity levels.