i need axis (i hope thats the name...my english isnt very flexible ; ) for a DC motor. on this axis will be human organ and this organ will be "scaned" with ultrasound. so i need material for axis that will be unvisible on ultrasound pictures. this organ and whole imaging is happening under water so i need material with same density (=1kg/1dm3) but material must be enough "hard" and must be homogenic (no "air bubbles" in himself, no "sponge-like, or swiss-cheese-like" material...)...
And this material is...?
And this material is...?
