Fig. 2: Continuous electrochemical fabrication and characterization of the smart Ag nanoparticles.

a Smart Ag nanoparticles were continuously formed at 30 V in aqueous solutions. The photos were captured from Supplementary Movie 1. b The absorption spectrum of the Ag nanoparticle colloid in water. Inset: Tyndall effect was observed when a laser beam passing through the colloidal solution. c Transmission electron microscope image of the prepared Ag nanoparticles at 30 V for 30 s. d The mean size of the Ag nanoparticles fabricated at different voltages. e The production efficiency of Ag nanoparticles in electrolytes with different SDS concentrations at 30 V. f Schematic of the formation process of the Ag nanoparticles. Process I: the nuclei are formed on the electrode surface passivated by dodecyl sulfate ions. Process II: The nanoparticles are negatively charged induced by the dodecyl sulfate ligands. Process III: The Ag nanoparticles are detached from the electrode surface. g Schematic of the forces exerted to the Ag nanoparticles on the electrode surface. f₁, f₂, and f₃ represent the shear force induced by the electrodynamic force and the formation/release of hydrogen bubbles, the electrostatic repulsive force between the nanoparticle and the electrode, and the adhesive force between the Ag nanoparticle and the electrode, respectively. h A large amount of Ag nanoparticles formed on the filtration membrane. i The electrochemical pen. Inset: an electrolyte droplet is formed by pushing the syringe, which can connect the anode and the cathode wires to generate Ag nanoparticles colloidal ink. j The ZJU letters can be written by the electrochemical pen on different substrates. k Repairing the broken circuit by the electrochemical pen. Error bars in (d, e) represent standard deviation of five independent measurements.