Nicholas R. Wood, Amanda I. Wolsiefer, Robert W. Cohn and Stuart J. Williams
The main figure shows a three-dimensional, branched fractal pattern of gold nanoparticles created via dielectrophoresis. Initially, a silver-gallium nanoneedle is mounted on the end of a pulled glass capillary and coated with a thin layer of gold. A conductive coverslip (not pictured) is used to complete the point-and-plate system. A droplet containing suspended non-spherical gold nanoparticles (35 nm mean diameter) of various shapes is introduced. At an AC signal of 200 kHz and 0.6 Vrms the gold nanoparticles are attracted to the probe via positive dielectrophoresis. Subsequent particle-particle electrokinetic interactions, including pearl-chaining, produce the resulting pattern. The inset figures (top, middle) are magnified images showing the trapped gold nanoparticles. The last inset image (bottom) shows a gold nanowire created from two electrodes.