Non-destructive pre- and post-experimental validation of glass nanopipette geometry: quantifying beam-induced deformation in membrane-free TEM

Nanopipettes have emerged as versatile tools for diverse applications, ranging from single-molecule sensing and nanoparticle detection to scanning probe microscopies such as scanning electrochemical microscopy and scanning ion conductance microscopy (SICM). In all these fields, precise geometrical characterization is a prerequisite for quantitative analysis. However, conventional "post-experimental" characterization cannot guarantee that the tip maintained its critical geometry during the experiment. While membrane-free transmission electron microscopy enables the non-destructive observation required for "pre- and post-experimental" validation, it introduces a risk of beam-induced deformation. In this study, we systematically investigated the deformation dynamics of quartz and borosilicate glass nanopipettes. Our analysis revealed distinct mechanisms: quartz exhibited continuous spheroidization enabled by structural homogeneity, whereas borosilicate glass showed fracture due to heterogeneity. Crucially, we identified a stable regime where deformation is negligible. By adhering to these conditions, we successfully demonstrated the rigorous tracking of a single quartz nanopipette's geometry both before and after live-cell SICM imaging. This workflow provides the first direct evidence of structural stability throughout the functional process, establishing a quantitative framework for reliable nanopipette metrology.