Superstability of micrometre jets surrounded by a polymeric shell.

We have produced superstable compound liquid microjets with a 3D-printed coaxial flow-focusing injector. The aqueous jet core is surrounded by a shell, a few hundred nanometres in thickness, of a low-concentration aqueous solution of a low-molecular-weight polymer. Due to the stabilizing effect of the polymeric shell, the minimum liquid flow rate leading to stable flow-focusing is decreased by one order of magnitude, resulting in much thinner and longer jets. Possible applications of this technique for serial femtosecond X-ray crystallography are discussed.