Currently direct Joule heating is the successful method for welding relatively large platinum nanowires. Also for nanowelding, which is similar to large-scale welding a solder is used to fuse the components together. But this method causes significant changes in the nanowire shape, or even complete break-up of the nanowire, due to severe local over-heating. To overcome this problem researchers of Sheffield University, UK have developed a simple method. This can be used to fabricate nanoelectronic test structures for research or to repair interconnects or other defects in circuits. The researchers positioned the wires such that their ends were touching but not their full lengths. Using a scanning electron microscope to view their work, they moved the wires with a nanomanipulator across the adjacent ends and electrically severed the sacrificial wire at two points, leaving a small bridge connecting the two nanowire ends and the bridge was welded into place by applying short voltage pulses inducing enough heat to fuse it to the nanowires. This nanowelding approach produces much better results than simply fusing together two nanowires without the use of solder.
Similarly when electron beam is focused on the overlapped nanowires they start welding together(example Au and Sn nanowires)
Florian Banhart of the University of Ulm in Germany soldered together two carbon nanotubes by focussing a narrow beam of electrons from a scanning electron microscope at the point where the tubes meet, thereby converting contaminants on their surfaces selectively at nanotube junctions into bridges made from graphite-like carbon that can conduct electricity.
A technique to weld conducting nanowires is by current-induced heating, i.e., Joule heating. A constant direct current is applied to the system, where the free ends of two nanowires are contacted, and the ends are successfully welded together to form a continuous straight nanowire. Welded nanowire can be cut at a point on the wire by supplying a high-current to the wire with a cone-shaped probe. Lap welding and a dissimilar metal weld can also be done.
By laying a nanowire across the objects that is wanted to weld and then passing just the right pulse of electricity through it the minuscule objects can be connected. Nanomanipulator is used to pick the wires up, move them around and electrify them so that the solder wire melts and flows onto the joint.