A method for forming atomic-scale contacts and atomic-scale gaps between two electrodes is disclosed. The method provides for applying a voltage between two electrodes in a circuit with a resistor. The applied voltage etches metal ions off one electrode and deposits the metal ions onto the second electrode. The metal ions are deposited on the sharpest point of the second electrode, causing the second electrode to grow towards the first electrode until an atomic-scale contact is formed. By increasing the magnitude of the resistor, the etching and deposition process will terminate prior to contact, forming an atomic-scale gap. The atomic-scale contacts and gaps formed according to this method are useful as a variety of nanosensors including chemical sensors, biosensors, hydrogen ion sensors, heavy metal ion sensors, magnetoresistive sensors, and molecular switches.