It is easy to make a metal hip or jaw implant, but hard to get it to match the flexibility of natural bone. That mismatch causes premature wear and failure. Now Afsaneh Rabiei, associate professor of mechanical, aerospace, and biomedical engineering at North Carolina State University, has found a way to make metal mimic the elastic modulus of natural bone. Not only is Rabiei's porous steel structure more flexible than other metal implants, but it is also lighter and its properties easier to control.