Non‐spherical colloidal nanoparticles have great potential for applications owing to their enhanced directional properties. However, the lack of methods to precisely assemble them on surfaces has hindered exploitation of their properties for planar devices. Here, the oriented assembly of short gold nanorods with lengths below 100 nm from colloidal suspensions is demonstrated. A locally induced phase transition confines the colloidal nanorods at a receding three‐phase contact line that is controllably moved over a nanostructured surface in a capillary assembly process. Dedicated topographical trapping sites allow for aligned assembly of the nanorods on the single‐particle level. The feasibility of this method is demonstrated by assembling nanorods into long‐range‐ordered, non‐close packed arrays that could serve as anti‐counterfeit labels by virtue of their distinct optical appearance in the far‐field. Furthermore, oriented nanorod dimers that are deterministically assembled have the potential to function as nano‐plasmonic antenna devices.

We have used a temperature sensitive polymer film as a removable template to position, and align, gold nanorods onto an underlying target substrate. Shape-matching guiding structures for the assembly of nanorods of size 80 nm × 25 nm have been written by thermal scanning probe lithography. The nanorods were assembled into the guiding structures, which determine both the position and the orientation of single nanorods, by means of capillary interactions. Following particle assembly, the polymer was removed cleanly by thermal decomposition and the nanorods are transferred to the underlying substrate. We have thus demonstrated both the placement and orientation of nanorods with an overall positioning accuracy of ≈10 nm onto an unstructured target substrate.

Capillary assembly was explored for the precise placement of 25 nm × 70 nm colloidal gold nanorods on prestructured poly(dimethylsiloxane) template surfaces. The concentration of nanorods and cationic surfactant cetyltrimethylammonium bromide (CTAB), the template wettability, and most critically the convective transport of the dispersed nanorods were tuned to study their effect on the resulting assembly yield. It is shown that gold nanorods can be placed into arrayed 120-nm diameter holes, achieving assembly yields as high as 95% when the local concentration of nanorods at the receding contact line is sufficiently high. Regular arrays of gold nanorods have several benefits over randomly deposited nanorod arrangements. Each assembled nanorod resides at a precisely defined location and can easily be found for subsequent characterization or direct utilization in a device. The former is illustrated by collecting scattering spectra from single nanorods and nanorod dimers, followed by subsequent SEM characterization without the need for intricate registration schemes.