Molecular dynamics simulation of localized electrochemical deposition

Localized electrochemical deposition (LED) of metals is the method of material addition used in electrochemical additive manufacturing (ECAM), an emerging nontraditional, additive manufacturing process which fabricates three-dimensional parts in a non-thermal, voxel-by-voxel manner. Control over output part characteristics requires a detailed understanding of the electrochemical deposition process, which ultimately arises from atomic time and size scale behaviors. This work demonstrates a molecular dynamics simulation of the LED process, including: setup of a heterogeneous metal-solution system with localized geometry, electrolyte modeling, application of referenced voltages to electrodes, and electrochemical metal deposition reactions. Output behavior - deposition rate, geometry, and current - was analyzed in response to changed voltage, electrolyte composition, and cell geometry to understand the localized deposition behavior at the atomic time and size scales. It was found that there was an optimal tool radius to simultaneously maximize the deposition speed and degree of localization. An increase in the voltage difference between the tool and substrate further improved the rate and overall localization of the deposition to a degree, but excessive voltage or low ion concentration resulted in ion depletion and a hollow geometry to form in the center of the deposition region.