Roughening orthopedic implants

But whether the implants are destined for the knee, a hip, a spine or a jaw, the silvery metal has one big drawback. Because it has a mirror surface, cells do not adhere to it very well, so implants are often roughened up before they are placed in the body.

A good way to roughen titanium is to etch nanotubes into it, since they provide a superb surface for bone cells to grasp onto as part of the healing process. But etching nanotubes in the titanium alloy is not cheap. Conventional techniques require platinum, which costs over $1,700 (£1,200) an ounce.

Now, however, through her PhD work with Prof Craig Friedrich, director of the Multi-scale Technologies Institute, Tolou Shokufar, a PhD candidate in Mechanical Engineering at Michigan Technological University, has developed a less expensive way to etch nanotubes into the titanium alloy.

In a weak solution of ammonium fluoride, she immerses two rods - one of the titanium alloy and another of copper - and hooks them up to a power source. An electrical current flows into the copper, through the solution and out through the titanium, creating a titanium-dioxide layer in the form of nanotubes about seven microns long and 100nm in diameter. Growing the ideal tube takes about two hours.