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Notable recent developments toward the realization of electronic nanocomputers have assembled logic circuits from semiconductor nanowires and individual carbon nanotube molecules. In spite of the broadly based and encouraging recent progress, a set of technical challenges still must be overcome to make a robust, commercially viable computer integrated on the molecular scale. The assembly of colloidal particles under an electric field offers many opportunities for the fabrication of ordered arrays, nanostructured films and microwires. We describe a method for the fabrication of gold nano/microstructures such as wires and dendrites on a lithographically patterned aluminium electrode with electric-field-induced assembly. The simple fabrication process will make these structures suitable for the miniaturisation of electronic circuits that can find application in sensors, actuators, and lab-on-a-chip devices. Our approach to electric-field-mediated fabrication exposes colloidal gold particles to the high electric field that can be generated between electrodes only 200 mm apart. We introduce an electric field of 100 Hz to 10 MHz by application of an alternating voltage of 5 to 10 V to the lithographically patterned microelectrodes. A suspension of gold nanoparticles of diameter 2.5 nm is added. We observe three types of fabrication, represented by three zones due to the different dielectophoretic force and convection effects. Some fibres grow through the liquid from one electrode toward the other, as could be seen in-situ by inverse optical microscopy. Dielectrophoretic-force-mediated fabrication, which is very flexible depending on the magnitudes of electric-field strength and frequency applied, has produced a notable advance in making mechanically flexible nano/microelectronic devices and led to a new understanding of the factors controlling the growth of nano/microstructures. When drops of suspension are patterned on the faces of components, three-dimensional structures can be generated. This type of system indicates how functional, self-assembling nano/microelectronic systems may be made. It provides a faster way of making devices, and the process can be very economical.
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