<i>In-situ</i> transmission electron microscopy shedding light on the mechanical properties of nanoscale materials

Characterizing the mechanical properties of nanomaterials (NMs) has always been a challenge for researchers due to their size effect and the difficulty of sample manipulation. In recent years, researchers have integrated scanning tunneling microscopy, atomic force microscopy and other techniques into transmission electron microscopy (TEM); thereby, advanced in-situ TEM nanomechanical measurement techniques for NMs have emerged. The study of mechanical properties using in-situ TEM allows a direct correlation among mechanical properties, atomic structures, and their dynamic processes. However, systematic reviews on these in-situ TEM measurement techniques, their working principles, and the corresponding results obtained by these methods are still limited. This review introduces the basic principles of recently developed in-situ TEM techniques (including TEM-atomic force microscopy and TEM-microelectromechanical systems), the features of these measurement techniques, the research progress in characterizing the mechanical properties and deformation behaviors of NMs by the in-situ TEM, and the influence of surface effects and defects on the mechanical properties of NMs. In perspective, several challenges regarding improving the in-situ TEM technique and analyzing the in-situ TEM data are addressed.