Current Status of Liquid Metal Printing

Abstract

This review focuses on the current state of the art in liquid metal additive manufacturing (AM), an emerging and growing family of related printing technologies used to fabricate near-net shape or fully free-standing metal objects. The various printing modes and droplet generation techniques as applied to liquid metals are discussed. Two different printing modes, continuous and drop-on-demand (DOD), exist for liquid metal printing and are based on commercial inkjet printing technology. Several techniques are in various stages of development from laboratory testing, prototyping, to full commercialization. Printing techniques include metal droplet generation by piezoelectric actuation or impact-driven, electrostatic, pneumatic, electrohydrodynamic (EHD), magnetohydrodynamic (MHD) ejection, or droplet generation by application of a high-power laser. The impetus for development of liquid metal printing was the precise, and often small scale, jetting of solder alloys for microelectronics applications. The fabrication of higher-melting-point metals and alloys and the printing of free-standing metal objects has provided further motivation for the research and development of liquid metal printing.

Ultrahigh-temperature melt printing of multi-principal element alloys

“…As a result, 3D printing MPEAs using a focused highenergy heating source typically requires the multi-elemental metals to be pre-alloyed, which adds extra processing costs [32][33][34] . As an alternative, direct liquid metal printing methods have been developed, in which the solid metals are melted by a printhead that is electrically preheated using copper coils 35,36 . However, the temperature of the copper heating coils is generally limited to <1000 K, constraining the range of metals that can be employed with this technique.…”

A Guide to Printed Stretchable Conductors

“…Furthermore, Marlin firmware is compatible with most of the commercially available 3D printing platforms used for extrusion printing. Other sources of pressure include thermal expansion and Lorentz force in the case of conductive fluids . Screw/auger extruders can help uniformly mix the ink, efficiently transfer thermal energy (important for materials that only flow at elevated temperatures), and to impart mechanical torque to push the ink from the nozzle …”

“…Other sources of pressure include thermal expansion 51 and Lorentz force in the case of conductive fluids. 52 Screw/auger extruders can help uniformly mix the ink, efficiently transfer thermal energy (important for materials that only flow at elevated temperatures), and to impart mechanical torque to push the ink from the nozzle. 53 To ensure continuous extrusion of a filament, it is imperative to tune the rheological properties of the ink, such as viscosity, storage modulus, yield stress and surface tension.…”

Influence of Salt Support Structures on Material Jetted Aluminum Parts

“…There is a wide variety of methods for droplet ejection in metal MJT, including piezoelectric, magnetohydrodynamic, pneumatic, impact-driven and laser-induced [ 21 ]. All samples for this investigation are printed on a pneumatically actuated drop on-demand MJT test stand with interchangeable print heads, that was originally developed for printing aluminum.…”