Metal 3D printing has enormous potential to revolutionize modern manufacturing. However, parts produced through the most popular metal printing processes, which use lasers to fuse together fine metal powder, often end up with gaps or defects. Researchers from the Lawrence Livermore National Laboratory are taking a new approach to metal 3D printing with a process they call direct metal writing, in which semisolid metal is directly extruded from a nozzle. The metal is engineered to be a shear thinning material, acting like a solid when standing still, and flowing like a liquid when a force is applied. The researchers produced parts using a bismuth-tin mixture, and are moving onto aluminum alloys - a metal that would be more attractive to industries such as aerospace and transportation.