Cryo-electron microscopy enables us to elucidate the structure of vitrified biological molecules and molecular assemblies, but does not allow the study of water-based processes as they occur, for example, in living organisms.
Graphene liquid cells (of the ‘veil-type’ variety) are a platform to stably encapsulate femtoliter droplets of water in the vacuum of the transmission electron microscope. As a 2D material, graphene induces minimal electron scattering and thus enables high resolution electron imaging of liquid cell contents, such as viruses and metallic nanoparticles.
In addition to the ‘veil-type’ graphene liquid cells, we also work on microfabricated designs, which can encapsulate larger volumes of liquid and can incorporate liquid flow and make experiments more reproducible.
A hurdle to high resolution imaging is the onset of beam damage under prolonged beam exposure. To limit exposure we use correlated light microscopy: fluorescent dye added to the liquid marks the cells clearly on a fluorescent image of the sample. Using specialized correlation software, the electron microscope then only exposes the cell long enough to record a high resolution image.