A chain of individual gold atoms

has about twice the tensile strength of bulk gold. A team of researchers from Madrid, Spain, and Lyngby, Denmark, drew a gold-tipped scanning tunneling microscope away from a gold cantilever to create a string of up to seven atoms. With a second STM placed under the cantilever, the researchers could observe a chain grow as the atoms in the gold electrodes rearranged to release a single atom at one end or the other. Eventually, when the force needed to rearrange the atoms became too great, the chain broke under the strain. That breaking force was about 1.5 nN, independent of chain length. To break a bond in bulk gold, by contrast, requires only 0.7-0.9 nN. The researchers also showed that the atomic chains have close to one quantum unit of electrical conductance and that the chains are elastically stiffer than the electrodes from which they arise. While it’s not yet...