Exploration of Direct-Ink-Write 3D Printing in Space: Droplet Dynamics and Patterns Formation in Microgravity

As a simple, fast and effective 3D printing method, direct-ink-writing (DIW) has potential applications in repairing the circuit board in orbit, printing the wearable devices for the astronaut, and producing the solar cells for the energy supply in space. To expand the DIW technology to space, we designed the colloidal material box (CMB) as the prototype printer of DIW and verified its applicability in the Chinese SJ-10 satellite. The colloidal suspensions was adopted as a diluted ink model to investigate two key processes of DIW under microgravity environment: manipulation of the droplet and formation of the patterns. We have showed the dynamics of the droplet, which would determine the size of the features, could be controlled through tuning the wettability of the needles and the solid surface. Compared to the ground, the "coffee ring" effect was weakened for the drying patterns because of strong interfacial effect under weightless conditions. We have found that fast evaporation could assist for fabricating more uniform and ordered structures