It has long been a rule of thumb that compressed metal results in a stronger substance - a technology that has driven blacksmith weaponry for centuries. The principle really took form when scientists began studying "tin whiskers" to understand why they were so sturdy despite their small size. Recently, using an in situ microscope, researchers at Lawrence Berkeley National Laboratory have been able to demonstrate what happens to metal dislocations at a microscopic level during compression.

"The first thing we observed was that, before the test, the nano-scale pillars of nickel were full of dislocations. But as we compressed the pillar, all the dislocations were driven out of the material - literally reducing the dislocation density by 15 orders of magnitude and producing a perfect crystal. We called this effect mechanical annealing." The research findings should lead to improvements in the strength of nano-technology machines.