Zeptoliter pipette delivers nanodroplets

Nanometer-sized droplets of liquid crystallize differently than their larger counterparts, according to a new study that challenges conventional theories of phase transformations and may lead to new techniques for manipulating microscopic droplets (Nat. Mater., DOI: 10.1038/nmat1894). Using high-temperature transmission electron microscopy methods, Brookhaven National Laboratory scientists Eli A. Sutter and Peter W. Sutter show that a gold-alloy-tipped germanium nanowire that is encapsulated in a carbon film can function as a pipette and dispense zeptoliter (10^-21 L) metal droplets (13-zL droplet shown). Heating the nanowire and quickly boring a tiny hole into the film with an electron beam causes spherical droplets of Au₇₂Ge₂₈ alloy to be delivered from the tip. A key finding of the study is that the nanodroplets crystallize by way of a surface-faceting process and not via the classic mechanism based on internal nucleation.