Electrochemical printing: software reconfigurable electrochemical microfabrication

Electrochemical printing (EcP) is a software reconfigurable tool and process for electrodeposition of multi-scale, multi-material objects from input drawings. The EcP system—comprising custom LabVIEW print driver software, hardware, electrolyte and a microjet print nozzle—creates complex patterns by locally electroplating individual metal and alloy dots as the microjet rasters over a substrate. The rastering of a microjet just a few microns above the substrate provides extraordinary convective mass transfer rates, allowing material growth rates that are routinely two orders of magnitude greater than in conventional plating. EcP has the flexibility to vary the print resolution and material composition during the patterning process via real time control of the microjet fly height, electrolyte flow rate and applied current. Microjet fly-height is used to vary the print resolution from 50 to 1000 dots per inch during the printing of a copper pattern. Simultaneous control of electrolyte flow rate and applied current through the microjet nozzle is used to achieve high plating efficiencies, well-formed dots and alloys of specific compositions for the copper and nickel–copper systems. It is also shown that commercially available noble metal plating baths can be used in the EcP tool, despite the unusually large current densities achievable and the complexity of commercial bath additives. Issues associated with making EcP a robust tool for 2D and 3D microfabrication are discussed.