  Conventional 3D printings are generally time-consuming and printable metal
inks are rather limited. From an alternative way, we proposed a liquid phase 3D
printing for quickly making metal objects. Through introducing metal alloys
whose melting point is slightly above room temperature as printing inks,
several representative structures spanning from one, two and three dimension to
more complex patterns were demonstrated to be quickly fabricated. Compared with
the air cooling in a conventional 3D printing, the liquid-phase-manufacturing
offers a much higher cooling rate and thus significantly improves the speed in
fabricating metal objects. This unique strategy also efficiently prevents the
liquid metal inks from air oxidation which is hard to avoid otherwise in an
ordinary 3D printing. Several key physical factors (like properties of the
cooling fluid, injection speed and needle diameter, types and properties of the
printing ink, etc.) were disclosed which would evidently affect the printing
quality. In addition, a basic route to make future liquid phase 3D printer
incorporated with both syringe pump and needle arrays was also suggested. The
liquid phase 3D printing method, which owns potential values not available in a
conventional modality, opens an efficient way for quickly making metal objects
in the coming time.
