A template for microwire self-assembly

Several methods exist for growing nanowires, whether attached to a substrate or dispersed in a liquid. Using those wires to make designated electrical connections in a circuit, however, has been difficult. Yves Galerne and his colleagues at the University of Strasbourg, France, now demonstrate a procedure that produces conducting wires across a gap between two electrodes. The chemical physicists first paint the electrodes with a polymer so as to create "anchors" in predetermined locations; when the gap is filled with nematic liquid crystals, an isolated defect line—a disclination—connects the anchors and therefore the electrodes. Next, silica particles coated with a conducting polymer are introduced and gather along the disclination like beads on a necklace. In the third step, a voltage across the electrodes welds the necklace beads together into a robust wire. Although ragged with extra polymer aggregates, the central region of a 150-micron-long wire, shown in the photo, demonstrates the team’s initial result. The researchers note that the wire’s size, smoothness, and conductivity can be improved—for example, by decreasing the silica particles’ size and concentration and by electroplating them. (J.-B. Fleury, D. Pires, Y. Galerne, Phys. Rev. Lett., in press.) —Stephen G. Benka