<p>Fabrication of pores at the atomic scale remains a significant challenge in modern nanotechnology, hindering the study of ion transport and molecular dynamics in confined spaces. Here, we introduce a chemically controllable break-membrane approach that enables the repeated formation and closure of nanoscale pores in SiN_x membranes through manipulating the in-pore electrochemical reaction conditions by transmembrane voltage. Ionic current measurements reveal distinct conductance features that are consistent with ion dehydration and transport through highly confined channels approaching sub-nanometer dimensions. The scalable nature of this platform, which allows multiple pores to be actuated simultaneously, offers a powerful tool for probing ion transport and fluid dynamics in extreme confinement. Beyond advancing fundamental understanding of ion transport and fluid dynamics, this chemically driven membrane system holds promise for applications in single-molecule sensing, neuromorphic computing, and nanoreactor design.</p>