The researchers behind the techniques say they can be used to assemble electronic components at smaller scales than have ever been possible.
One technique, called "nanorobotic" spot welding, uses molten copper to join up objects in the same way that a human electrician might use solder.
"We position a 50-nanometre-wide carbon nanotube filled with copper inside a nanorobotic manipulator, and run a small voltage through it to melt the copper," explains Dong. In experiments the researchers positioned the manipulator so the melting metal connected one carbon nanotube to another.
Dong says he expects the technique to be useful for building electronic devices. "The copper can be used to make electrical connections with low resistance," he told New Scientist. That could connect nanotubes into tiny transistors, the current-switching building blocks of most electronic devices, he says.