Aligning Nanowires by Standing Surface Acoustic Waves

We present a standing surface acoustic wave (SSAW) based approach to achieve one-dimensional (1D) and two-dimensional (2D) alignment of nanowires (NWs). Our SSAW-based nanowire-aligning technique can be used to construct large-scale (e.g., centimeter scale) network of nanowires within 5 min. In this approach, we use interdigital transducers deposited on a piezoelectric substrate to generate different standing SAW fields, which induce AC electric fields on the substrate and in turn align suspended metallic nanowires in the fluidic chamber. This effect is coined as standing SAW-induced dielectrophoresis (DEP). By controlling the standing SAW field, we show that metallic nanowires can be bundled and aligned in one-dimensional (1D) standing SAW fields, or assembled into networks in two-dimensional (2D) standing SAW fields. We can achieve different patterns of nanowires by changing the distribution of pressure and electric field with different arrangements of interdigital transducers (IDTs). Moreover, three-dimensional (3D) spinning of nanowires are observed near the acoustic pressure antinodes of a 2D standing SAW field. The technique presented in this paper possesses advantages of tunability, high throughput, and low cost, which has the potential to be adopted in electrical, optical, and biological applications.