EngeniusMicro currently utilizes drop-on-demand printing technology through the use of a Fujifilm Dimatix Materials Printer. The Dimatix prints conductive inks on a variety of substrates from as thin as a few microns up to 25mm thickness using 16 MEMS jets to precisely deposit inks onto the substrate. The print is then submitted to post processing to sinter the conductive particles in the ink while evaporating away solvents and other volatiles. Substrate is held in place by way of vacuum table that can also be heated to provide extra control over materials conditions while printing. Using the appropriate recipe this printer can produce traces as narrow as 10 and 5 micron gaps between traces. EngeniusMicro has printed a number of flexible circuits in addition to advanced sensors specifically developed to be printed on flexible materials using conductive inks.
EngeniusMicro has also developed our own ink dispensing print head called the MicroDispense. It utilizes positive pressure and a needle valve to accurately dispense incredibly detailed patterns, and circuits on the substrate. The MicroDispense print head currently operates on a 3-axis CNC mill, replacing the conventional tool head. The technology was developed in-house with many of the components, such as valves and nozzles, created and printed using our SLA resin printers. These printers are able to quickly produce circuits on par with medium density circuit boards produced through conventional photoresist and etch manufacturing methods.
There are several formulations of conductive inks utilized in the printing of electronics such as Silver Jet DGP45 HTG which is designed cure at temperatures between 400º-550ºC, while producing electronic circuits with fine pitch traces and lines comparable with photolithography. These types of inks use solvents to facilitate flow and wetting during application. These solvents may be alcohol based or may simply be water and will need to be cured through post processing.
Inks dispensed through the MicroDispense are of a thicker consistency and consist of silver nano particles suspended in a quick skinning polyurethane allowing the inks to be self-supporting. These inks cure at room temperature to full hardness within 24 hours. This allows the inks to printed in a fashion more consistent with conventional methods used for polymer 3D printing. These inks often need to be cured in a post-process whether that is the curing and solidification of a binding element or the evaporation of a solvent. This will need to have special attention given the environmental requirements of operating in space.
Options exist for post-processing including furnace sintering, photonic curing, and precision laser sintering. Furnace curing may be the simplest given the expected heating requirements for other additive manufacturing processes assumed to be taking place in the same space, though processes like photonic or laser curing may provide more controlled and efficient curing of the inks. Photonic and laser curing offer the advantage of not heating the entire substrate when multi-material processing has occurred.. Specific trades will need to be performed in order to identify the process most appropriate for the chosen printing process and materials.
While producing printed electronics in microgravity poses similar challenges in regard to thermal management, materials management, and management of any volatiles produced during the curing process, EngeniusMicro has the experience and technical expertise to develop the capability to print conductive materials in space.