Nanotube squeeze play

Controlled electron irradiation can transform multiwalled carbon nanotubes (MWNTs) into tiny high-pressure chambers, according to an international team led by Florian Banhart and Litao Sun of Germany's University of Mainz (Science 2006, 312, 1199). Irradiating an MWNT at high temperature knocks carbon atoms out of the material's characteristic carbon lattice. The nanotube restores this atomic network and heals itself by contracting, creating pressures up to 40 gigapascal within its core in the process. When Banhart and Sun's group filled the MWNTs with iron carbide or cobalt nanowires and irradiated the assembly, they found that the contracting tubes could squeeze the solid material like toothpaste through a tube (shown with an Fe₃C nanowire). Because the technique uses transmission electron microscopy to induce the MWNT's self-compression, it offers researchers a way to directly observe pressure-induced atomic motion. This is in contrast with diamond anvil compression techniques, which rely on spectroscopic techniques to study materials under high pressure.