Seems like it's related to a breakthrough for X-ray Photoelectron Spectroscopy that was originally thought to not be possible for liquids because it depends on

Seems like it's related to a breakthrough for X-ray Photoelectron Spectroscopy that was originally thought to not be possible for liquids because it depends on having a vacuum, and the liquid would just evaporate. The solution was to use a microjet to spray a thin line of liquid, within the vacuum and cross that with the x-ray beam.