Lithographically-directed self-assembly of nanostructures

The combination of lithography and self-assembly provides a powerful means of organizing solution-synthesized nanostructures for a wide variety of applications. We have developed a fluidic assembly method that relies on the local pinning of a moving liquid contact line by lithographically produced topographic features to concentrate nanoparticles at those features. The final stages of the assembly process are controlled first by long-range immersion capillary forces and then by the short-range electrostatic and Van der Waal's interactions. We have successfully assembled nanoparticles from 50 nm to 2 nm in size using this technique and have also demonstrated the controlled positioning of more complex nanotetrapod structures. We have used this process to assemble Au nanoparticles into pre-patterned electrode structures and have performed preliminary electrical characterization of the devices so formed. The fluidic assembly method is capable of very high yield, in terms of positioning nanostructures at each lithographically-defined location, and of excellent specificity, with essentially no particle deposition between features.