(A) Illustration of a conductive particle attracted to a disclination line that joins two electrodes at points P and Q. (B) Photograph of a horizontal necklace of particles. The red bar is 30 micrometers long. Image copyright: Fleury, et al. (c)2009 APS.

Scientists have demonstrated a new microwire fabrication technique in which microwires self-assemble themselves in a three-dimensional template made of nematic liquid crystals. Amidst concerns about Moore’s law eventually approaching a limit in two dimensions, the new fabrication method could enable researchers to continue to increase the density of transistors on integrated circuits by making use of the third dimension.

As the researchers explain, many different processes have been proposed in the past few years for fabricating high-quality nanowires. Generally, in order to connect nanowires to electrodes, researchers must confine them on a two-dimensional substrate and use the third dimension for manipulating the connections, often using a computer.

In their new study, the scientists show how to manufacture microwires that self-assemble themselves in a three-dimensional template and then connect themselves to electrodes with an accuracy of a few micrometers. First, the researchers took the two substrates to be connected, and filled the space between them with a nematic liquid crystal, which is the same substance used in many kinds of LCDs. Although the molecules in the liquid are free to move, they align themselves parallel to one another, except along threadlike (defect) lines (“nemato” in Greek means “threadlike”).

Next, the scientists created a defect line in the nematic liquid crystal that runs between electrodes in the two substrates. By rubbing the substrates in three different locations at a specific angle, the researchers produced a programmable disclination (i.e., a topological singularity or defect line). In this area, the molecules cannot orient themselves in any direction, creating a disclination that extends between the two substrates.