https://phys.org/news/2018-05-line-narrower-cold-virus.html

Oak Ridge National Laboratory (ORNL) researchers at the Center for Nanophase Materials Sciences rastered a highly focused helium-ion beam through a thin layer of precursor solution, causing site-specific platinum deposition in a controlled manner.

This direct-write technique enabled nanofabrication of high-purity metallic ribbons only 15 nanometers wide—narrower than a cold virus. This work was the first demonstration of direct-write nanofabrication using an ion-beam microscope to direct chemical reactions in a liquid cell, or environmental chamber encapsulating a sample in liquid. It would not have been possible to directly write these highly precise, high-purity metallic structures without a full understanding from experiment and theory.