A Nanofluidic Platform for In-situ Electron Microscopy of Processes in Liquid Media
Joseph M. Grogan and Haim H. Bau
Until recently, it was not possible to observe phenomena taking place in a liquid medium, such as the formation of colloidal crystals, with the high resolution of the electron microscope.
We have developed a microfabricated chip, dubbed the nanoaquarium, for in-situ, direct observations of dynamical processes in liquid media with a transmission (TEM) and scanning transmission (STEM) electron microscope.
The nanoaquarium consists of a flow cell with a height of tens of nanometers, sandwiched between two thin silicon nitride membranes. The sample cross-section is extremely thin to minimize electron scattering by the suspending fluid, and the device is hermetically sealed and leak-proof to prevent sample evaporation in the high vacuum microscope chamber. The flow cell is equipped with electrodes for actuation and sensing.
Aqueous solutions containing 50 nm gold particles (left) and 5 nm gold particles (right) have been studied in the device. Thermal motion of the particles as well as particle self-assembly have been observed, demonstrating that the nanoaquarium is an effective tool for real-time observations of nanoscale processes in liquid media.