There is a company called fabrisonic that uses sound waves to essentially weave different metals together but they also have a process which is almost reverse 3d printing by removing parts of the metal. They said in a documentary that they also produce metal parts for nasa where they need liquid or gas channels inside of a sealed object, by using their method of creating the objects as one piece they can make objects that will be more able to handle strong environmental shifts in pressure and temperature however they do not have the reduced weight capacity that some of those other semi hollow devices and these new meta shapes have , however they can create objects which normally wouldn’t be able to exist.