Credit: © 2008 AIP

Integrating nanoparticles with silicon-based devices is a major hurdle in the development of nanoscale electronics. For example, mass production techniques that can precisely place individual carbon nanotubes at specific locations on silicon-chips remain elusive. Now, Dimos Poulikakos and colleagues1 at the Swiss Federal Institute of Technology, Zurich, have developed an automated method — combining a fountain-pen-like micropipette and electric-field gradients — for locating single carbon nanotubes at predefined locations between platinum electrodes.

Micropipettes with orifices of 1–10 µm were filled with solutions of multiwall carbon nanotubes and, by precise x–y–z translation, microdroplets were squeezed out between two platinum electrodes that were separated by a gap of 300 nm. Application of an electric-field gradient between the electrodes then caused the carbon nanotubes to move and come to rest across the metallic gap due to dielectrophorosis — forces acting on uncharged particles located in non-uniform electric fields. Finally, the micropipette was retracted, after which the microdroplets evaporated leaving the nanotubes in the desired location.

The researchers also showed that the micropipette acted as a filter, preventing deposition of unwanted carbon-nanotube bundles. Furthermore, the team expect that the method is not confined to carbon nanotubes and could be applicable for many other materials.