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When an aqueous suspension of metallic nanoparticles is placed in an alternating current field generated between two planar electrodes, the particles quickly assemble into conducting microwires that grow from one electrode to the other [Science, 294, 1082 (2001)]. The wires, which are micrometers in diameter and millimeters in length, can grow faster than 50 mm per second, according to chemical engineers Eric W. Kaler of the University of Delaware and Orlin D. Velev of North Carolina State University and their coworkers. The method provides a quick and simple way to create electrical connections in watery environments under ambient conditions, they point out. The connections are self-repairing--that is, if the current is increased until it burns a gap in the wire, new nanoparticles immediately start assembling at the wire's tip, restoring the electrical connection. When mixed suspensions of metallic particles and polystyrene latex microspheres are placed in the alternating current field, latex-coated microwires are produced. The researchers believe such structures hold promise for wet electronic and bioelectronic circuits, including chemical sensors
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