Achieving High Spatial Resolution Transmission Electron Microscopy Studies in Closed Liquid Cells.

Liquid cell transmission electron microscopy (LCTEM) is a rising technique for probing dynamic processes and structural transformations in liquid environments at the nanoscale. However, its broader application is largely constrained by limited spatial resolution, which arises from electron scattering by the encapsulating membranes and the liquid layer. Recent advances in instrument design, micro-electro-mechanical system (MEMS)-based cells, and ultrathin window materials have substantially improved imaging quality, yet achieving atomic-scale resolution in liquids remains a formidable challenge. This review provides a comprehensive overview of such strategies developed to enhance the spatial resolution of LCTEM, emphasizing the roles of liquid layer thickness, MEMS design, and cell configuration. We highlight representative approaches, such as reducing liquid and membrane thicknesses, optimizing MEMS architectures, and employing grid-based liquid cells, and discuss their underlying mechanisms and recent progress. Finally, we outline current challenges and future opportunities for achieving high-resolution, multifunctional LCTEM systems capable of capturing dynamic processes in realistic liquid environments.