We have demonstrated the confined high-resolution direct additive writing of copper nanostructures by using a biased AFM tip in a dilute electrolyte, where the tip is in intermittent contact with the substrate through the oscillation of the cantilever. We find a particularly intriguing critical dependence of deposition on the tapping dynamics of the AFM and ion concentration. We propose a confinement mechanism that balances access of ions and shaping of the electrochemical potential in the tip-substrate gap. While this method is expected to be general for the electrochemical deposition of a variety of materials, opening up new routes for nanofabrication, probing local reactions through topography provides a way to understand the local dynamics and charge transfer at the electrical double layer, such as the Debye time.