Transmission electron microscopy (TEM) has long been an essential tool for understanding the structure of materials. Over the past couple of decades, this venerable technique has undergone a number of revolutions, such as the development of aberration correction for atomic level imaging, the realization of cryogenic TEM for imaging biological specimens, and new instrumentation permitting the observation of dynamic systems
in situ
. Research in the latter has rapidly accelerated in recent years, based on a silicon-chip architecture that permits a versatile array of experiments to be performed under the high vacuum of the TEM. Of particular interest is using these silicon chips to enclose fluids safely inside the TEM, allowing us to observe liquid dynamics at the nanoscale.
In situ
imaging of liquid phase reactions under TEM can greatly enhance our understanding of fundamental processes in fields from electrochemistry to cell biology. Here, we review how
in situ
TEM experiments of liquids can be performed, with a particular focus on microchip-encapsulated liquid cell TEM. We will cover the basics of the technique, and its strengths and weaknesses with respect to related
in situ
TEM methods for characterizing liquid systems. We will show how this technique has provided unique insights into nanomaterial synthesis and manipulation, battery science and biological cells. A discussion on the main challenges of the technique, and potential means to mitigate and overcome them, will also be presented.
Low Voltage Transmission Electron Microscopy in Cell Biology